text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   *  Digital Audio (PCM) abstract layer
   *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
   *                   Abramo Bagnara <abramo@alsa-project.org>
   */
  
  #include <linux/slab.h>
  #include <linux/sched/signal.h>
  #include <linux/time.h>
  #include <linux/math64.h>
  #include <linux/export.h>
  #include <sound/core.h>
  #include <sound/control.h>
  #include <sound/tlv.h>
  #include <sound/info.h>
  #include <sound/pcm.h>
  #include <sound/pcm_params.h>
  #include <sound/timer.h>
  
  #include "pcm_local.h"
  
  #ifdef CONFIG_SND_PCM_XRUN_DEBUG
  #define CREATE_TRACE_POINTS
  #include "pcm_trace.h"
  #else
  #define trace_hwptr(substream, pos, in_interrupt)
  #define trace_xrun(substream)
  #define trace_hw_ptr_error(substream, reason)
  #define trace_applptr(substream, prev, curr)
  #endif
  
  static int fill_silence_frames(struct snd_pcm_substream *substream,
  			       snd_pcm_uframes_t off, snd_pcm_uframes_t frames);
  
  /*
   * fill ring buffer with silence
   * runtime->silence_start: starting pointer to silence area
   * runtime->silence_filled: size filled with silence
   * runtime->silence_threshold: threshold from application
   * runtime->silence_size: maximal size from application
   *
   * when runtime->silence_size >= runtime->boundary - fill processed area with silence immediately
   */
  void snd_pcm_playback_silence(struct snd_pcm_substream *substream, snd_pcm_uframes_t new_hw_ptr)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	snd_pcm_uframes_t frames, ofs, transfer;
  	int err;
  
  	if (runtime->silence_size < runtime->boundary) {
  		snd_pcm_sframes_t noise_dist, n;
  		snd_pcm_uframes_t appl_ptr = READ_ONCE(runtime->control->appl_ptr);
  		if (runtime->silence_start != appl_ptr) {
  			n = appl_ptr - runtime->silence_start;
  			if (n < 0)
  				n += runtime->boundary;
  			if ((snd_pcm_uframes_t)n < runtime->silence_filled)
  				runtime->silence_filled -= n;
  			else
  				runtime->silence_filled = 0;
  			runtime->silence_start = appl_ptr;
  		}
  		if (runtime->silence_filled >= runtime->buffer_size)
  			return;
  		noise_dist = snd_pcm_playback_hw_avail(runtime) + runtime->silence_filled;
  		if (noise_dist >= (snd_pcm_sframes_t) runtime->silence_threshold)
  			return;
  		frames = runtime->silence_threshold - noise_dist;
  		if (frames > runtime->silence_size)
  			frames = runtime->silence_size;
  	} else {
  		if (new_hw_ptr == ULONG_MAX) {	/* initialization */
  			snd_pcm_sframes_t avail = snd_pcm_playback_hw_avail(runtime);
  			if (avail > runtime->buffer_size)
  				avail = runtime->buffer_size;
  			runtime->silence_filled = avail > 0 ? avail : 0;
  			runtime->silence_start = (runtime->status->hw_ptr +
  						  runtime->silence_filled) %
  						 runtime->boundary;
  		} else {
  			ofs = runtime->status->hw_ptr;
  			frames = new_hw_ptr - ofs;
  			if ((snd_pcm_sframes_t)frames < 0)
  				frames += runtime->boundary;
  			runtime->silence_filled -= frames;
  			if ((snd_pcm_sframes_t)runtime->silence_filled < 0) {
  				runtime->silence_filled = 0;
  				runtime->silence_start = new_hw_ptr;
  			} else {
  				runtime->silence_start = ofs;
  			}
  		}
  		frames = runtime->buffer_size - runtime->silence_filled;
  	}
  	if (snd_BUG_ON(frames > runtime->buffer_size))
  		return;
  	if (frames == 0)
  		return;
  	ofs = runtime->silence_start % runtime->buffer_size;
  	while (frames > 0) {
  		transfer = ofs + frames > runtime->buffer_size ? runtime->buffer_size - ofs : frames;
  		err = fill_silence_frames(substream, ofs, transfer);
  		snd_BUG_ON(err < 0);
  		runtime->silence_filled += transfer;
  		frames -= transfer;
  		ofs = 0;
  	}
  }
  
  #ifdef CONFIG_SND_DEBUG
  void snd_pcm_debug_name(struct snd_pcm_substream *substream,
  			   char *name, size_t len)
  {
  	snprintf(name, len, "pcmC%dD%d%c:%d",
  		 substream->pcm->card->number,
  		 substream->pcm->device,
  		 substream->stream ? 'c' : 'p',
  		 substream->number);
  }
  EXPORT_SYMBOL(snd_pcm_debug_name);
  #endif
  
  #define XRUN_DEBUG_BASIC	(1<<0)
  #define XRUN_DEBUG_STACK	(1<<1)	/* dump also stack */
  #define XRUN_DEBUG_JIFFIESCHECK	(1<<2)	/* do jiffies check */
  
  #ifdef CONFIG_SND_PCM_XRUN_DEBUG
  
  #define xrun_debug(substream, mask) \
  			((substream)->pstr->xrun_debug & (mask))
  #else
  #define xrun_debug(substream, mask)	0
  #endif
  
  #define dump_stack_on_xrun(substream) do {			\
  		if (xrun_debug(substream, XRUN_DEBUG_STACK))	\
  			dump_stack();				\
  	} while (0)
  
  /* call with stream lock held */
  void __snd_pcm_xrun(struct snd_pcm_substream *substream)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  
  	trace_xrun(substream);
  	if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE) {
  		struct timespec64 tstamp;
  
  		snd_pcm_gettime(runtime, &tstamp);
  		runtime->status->tstamp.tv_sec = tstamp.tv_sec;
  		runtime->status->tstamp.tv_nsec = tstamp.tv_nsec;
  	}
  	snd_pcm_stop(substream, SNDRV_PCM_STATE_XRUN);
  	if (xrun_debug(substream, XRUN_DEBUG_BASIC)) {
  		char name[16];
  		snd_pcm_debug_name(substream, name, sizeof(name));
  		pcm_warn(substream->pcm, "XRUN: %s\n", name);
  		dump_stack_on_xrun(substream);
  	}
  }
  
  #ifdef CONFIG_SND_PCM_XRUN_DEBUG
  #define hw_ptr_error(substream, in_interrupt, reason, fmt, args...)	\
  	do {								\
  		trace_hw_ptr_error(substream, reason);	\
  		if (xrun_debug(substream, XRUN_DEBUG_BASIC)) {		\
  			pr_err_ratelimited("ALSA: PCM: [%c] " reason ": " fmt, \
  					   (in_interrupt) ? 'Q' : 'P', ##args);	\
  			dump_stack_on_xrun(substream);			\
  		}							\
  	} while (0)
  
  #else /* ! CONFIG_SND_PCM_XRUN_DEBUG */
  
  #define hw_ptr_error(substream, fmt, args...) do { } while (0)
  
  #endif
  
  int snd_pcm_update_state(struct snd_pcm_substream *substream,
  			 struct snd_pcm_runtime *runtime)
  {
  	snd_pcm_uframes_t avail;
  
  	avail = snd_pcm_avail(substream);
  	if (avail > runtime->avail_max)
  		runtime->avail_max = avail;
  	if (runtime->status->state == SNDRV_PCM_STATE_DRAINING) {
  		if (avail >= runtime->buffer_size) {
  			snd_pcm_drain_done(substream);
  			return -EPIPE;
  		}
  	} else {
  		if (avail >= runtime->stop_threshold) {
  			__snd_pcm_xrun(substream);
  			return -EPIPE;
  		}
  	}
  	if (runtime->twake) {
  		if (avail >= runtime->twake)
  			wake_up(&runtime->tsleep);
  	} else if (avail >= runtime->control->avail_min)
  		wake_up(&runtime->sleep);
  	return 0;
  }
  
  static void update_audio_tstamp(struct snd_pcm_substream *substream,
  				struct timespec64 *curr_tstamp,
  				struct timespec64 *audio_tstamp)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	u64 audio_frames, audio_nsecs;
  	struct timespec64 driver_tstamp;
  
  	if (runtime->tstamp_mode != SNDRV_PCM_TSTAMP_ENABLE)
  		return;
  
  	if (!(substream->ops->get_time_info) ||
  		(runtime->audio_tstamp_report.actual_type ==
  			SNDRV_PCM_AUDIO_TSTAMP_TYPE_DEFAULT)) {
  
  		/*
  		 * provide audio timestamp derived from pointer position
  		 * add delay only if requested
  		 */
  
  		audio_frames = runtime->hw_ptr_wrap + runtime->status->hw_ptr;
  
  		if (runtime->audio_tstamp_config.report_delay) {
  			if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
  				audio_frames -=  runtime->delay;
  			else
  				audio_frames +=  runtime->delay;
  		}
  		audio_nsecs = div_u64(audio_frames * 1000000000LL,
  				runtime->rate);
  		*audio_tstamp = ns_to_timespec64(audio_nsecs);
  	}
  
  	if (runtime->status->audio_tstamp.tv_sec != audio_tstamp->tv_sec ||
  	    runtime->status->audio_tstamp.tv_nsec != audio_tstamp->tv_nsec) {
  		runtime->status->audio_tstamp.tv_sec = audio_tstamp->tv_sec;
  		runtime->status->audio_tstamp.tv_nsec = audio_tstamp->tv_nsec;
  		runtime->status->tstamp.tv_sec = curr_tstamp->tv_sec;
  		runtime->status->tstamp.tv_nsec = curr_tstamp->tv_nsec;
  	}
  
  
  	/*
  	 * re-take a driver timestamp to let apps detect if the reference tstamp
  	 * read by low-level hardware was provided with a delay
  	 */
  	snd_pcm_gettime(substream->runtime, &driver_tstamp);
  	runtime->driver_tstamp = driver_tstamp;
  }
  
  static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
  				  unsigned int in_interrupt)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	snd_pcm_uframes_t pos;
  	snd_pcm_uframes_t old_hw_ptr, new_hw_ptr, hw_base;
  	snd_pcm_sframes_t hdelta, delta;
  	unsigned long jdelta;
  	unsigned long curr_jiffies;
  	struct timespec64 curr_tstamp;
  	struct timespec64 audio_tstamp;
  	int crossed_boundary = 0;
  
  	old_hw_ptr = runtime->status->hw_ptr;
  
  	/*
  	 * group pointer, time and jiffies reads to allow for more
  	 * accurate correlations/corrections.
  	 * The values are stored at the end of this routine after
  	 * corrections for hw_ptr position
  	 */
  	pos = substream->ops->pointer(substream);
  	curr_jiffies = jiffies;
  	if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE) {
  		if ((substream->ops->get_time_info) &&
  			(runtime->audio_tstamp_config.type_requested != SNDRV_PCM_AUDIO_TSTAMP_TYPE_DEFAULT)) {
  			substream->ops->get_time_info(substream, &curr_tstamp,
  						&audio_tstamp,
  						&runtime->audio_tstamp_config,
  						&runtime->audio_tstamp_report);
  
  			/* re-test in case tstamp type is not supported in hardware and was demoted to DEFAULT */
  			if (runtime->audio_tstamp_report.actual_type == SNDRV_PCM_AUDIO_TSTAMP_TYPE_DEFAULT)
  				snd_pcm_gettime(runtime, &curr_tstamp);
  		} else
  			snd_pcm_gettime(runtime, &curr_tstamp);
  	}
  
  	if (pos == SNDRV_PCM_POS_XRUN) {
  		__snd_pcm_xrun(substream);
  		return -EPIPE;
  	}
  	if (pos >= runtime->buffer_size) {
  		if (printk_ratelimit()) {
  			char name[16];
  			snd_pcm_debug_name(substream, name, sizeof(name));
  			pcm_err(substream->pcm,
  				"invalid position: %s, pos = %ld, buffer size = %ld, period size = %ld\n",
  				name, pos, runtime->buffer_size,
  				runtime->period_size);
  		}
  		pos = 0;
  	}
  	pos -= pos % runtime->min_align;
  	trace_hwptr(substream, pos, in_interrupt);
  	hw_base = runtime->hw_ptr_base;
  	new_hw_ptr = hw_base + pos;
  	if (in_interrupt) {
  		/* we know that one period was processed */
  		/* delta = "expected next hw_ptr" for in_interrupt != 0 */
  		delta = runtime->hw_ptr_interrupt + runtime->period_size;
  		if (delta > new_hw_ptr) {
  			/* check for double acknowledged interrupts */
  			hdelta = curr_jiffies - runtime->hw_ptr_jiffies;
  			if (hdelta > runtime->hw_ptr_buffer_jiffies/2 + 1) {
  				hw_base += runtime->buffer_size;
  				if (hw_base >= runtime->boundary) {
  					hw_base = 0;
  					crossed_boundary++;
  				}
  				new_hw_ptr = hw_base + pos;
  				goto __delta;
  			}
  		}
  	}
  	/* new_hw_ptr might be lower than old_hw_ptr in case when */
  	/* pointer crosses the end of the ring buffer */
  	if (new_hw_ptr < old_hw_ptr) {
  		hw_base += runtime->buffer_size;
  		if (hw_base >= runtime->boundary) {
  			hw_base = 0;
  			crossed_boundary++;
  		}
  		new_hw_ptr = hw_base + pos;
  	}
        __delta:
  	delta = new_hw_ptr - old_hw_ptr;
  	if (delta < 0)
  		delta += runtime->boundary;
  
  	if (runtime->no_period_wakeup) {
  		snd_pcm_sframes_t xrun_threshold;
  		/*
  		 * Without regular period interrupts, we have to check
  		 * the elapsed time to detect xruns.
  		 */
  		jdelta = curr_jiffies - runtime->hw_ptr_jiffies;
  		if (jdelta < runtime->hw_ptr_buffer_jiffies / 2)
  			goto no_delta_check;
  		hdelta = jdelta - delta * HZ / runtime->rate;
  		xrun_threshold = runtime->hw_ptr_buffer_jiffies / 2 + 1;
  		while (hdelta > xrun_threshold) {
  			delta += runtime->buffer_size;
  			hw_base += runtime->buffer_size;
  			if (hw_base >= runtime->boundary) {
  				hw_base = 0;
  				crossed_boundary++;
  			}
  			new_hw_ptr = hw_base + pos;
  			hdelta -= runtime->hw_ptr_buffer_jiffies;
  		}
  		goto no_delta_check;
  	}
  
  	/* something must be really wrong */
  	if (delta >= runtime->buffer_size + runtime->period_size) {
  		hw_ptr_error(substream, in_interrupt, "Unexpected hw_ptr",
  			     "(stream=%i, pos=%ld, new_hw_ptr=%ld, old_hw_ptr=%ld)\n",
  			     substream->stream, (long)pos,
  			     (long)new_hw_ptr, (long)old_hw_ptr);
  		return 0;
  	}
  
  	/* Do jiffies check only in xrun_debug mode */
  	if (!xrun_debug(substream, XRUN_DEBUG_JIFFIESCHECK))
  		goto no_jiffies_check;
  
  	/* Skip the jiffies check for hardwares with BATCH flag.
  	 * Such hardware usually just increases the position at each IRQ,
  	 * thus it can't give any strange position.
  	 */
  	if (runtime->hw.info & SNDRV_PCM_INFO_BATCH)
  		goto no_jiffies_check;
  	hdelta = delta;
  	if (hdelta < runtime->delay)
  		goto no_jiffies_check;
  	hdelta -= runtime->delay;
  	jdelta = curr_jiffies - runtime->hw_ptr_jiffies;
  	if (((hdelta * HZ) / runtime->rate) > jdelta + HZ/100) {
  		delta = jdelta /
  			(((runtime->period_size * HZ) / runtime->rate)
  								+ HZ/100);
  		/* move new_hw_ptr according jiffies not pos variable */
  		new_hw_ptr = old_hw_ptr;
  		hw_base = delta;
  		/* use loop to avoid checks for delta overflows */
  		/* the delta value is small or zero in most cases */
  		while (delta > 0) {
  			new_hw_ptr += runtime->period_size;
  			if (new_hw_ptr >= runtime->boundary) {
  				new_hw_ptr -= runtime->boundary;
  				crossed_boundary--;
  			}
  			delta--;
  		}
  		/* align hw_base to buffer_size */
  		hw_ptr_error(substream, in_interrupt, "hw_ptr skipping",
  			     "(pos=%ld, delta=%ld, period=%ld, jdelta=%lu/%lu/%lu, hw_ptr=%ld/%ld)\n",
  			     (long)pos, (long)hdelta,
  			     (long)runtime->period_size, jdelta,
  			     ((hdelta * HZ) / runtime->rate), hw_base,
  			     (unsigned long)old_hw_ptr,
  			     (unsigned long)new_hw_ptr);
  		/* reset values to proper state */
  		delta = 0;
  		hw_base = new_hw_ptr - (new_hw_ptr % runtime->buffer_size);
  	}
   no_jiffies_check:
  	if (delta > runtime->period_size + runtime->period_size / 2) {
  		hw_ptr_error(substream, in_interrupt,
  			     "Lost interrupts?",
  			     "(stream=%i, delta=%ld, new_hw_ptr=%ld, old_hw_ptr=%ld)\n",
  			     substream->stream, (long)delta,
  			     (long)new_hw_ptr,
  			     (long)old_hw_ptr);
  	}
  
   no_delta_check:
  	if (runtime->status->hw_ptr == new_hw_ptr) {
  		runtime->hw_ptr_jiffies = curr_jiffies;
  		update_audio_tstamp(substream, &curr_tstamp, &audio_tstamp);
  		return 0;
  	}
  
  	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK &&
  	    runtime->silence_size > 0)
  		snd_pcm_playback_silence(substream, new_hw_ptr);
  
  	if (in_interrupt) {
  		delta = new_hw_ptr - runtime->hw_ptr_interrupt;
  		if (delta < 0)
  			delta += runtime->boundary;
  		delta -= (snd_pcm_uframes_t)delta % runtime->period_size;
  		runtime->hw_ptr_interrupt += delta;
  		if (runtime->hw_ptr_interrupt >= runtime->boundary)
  			runtime->hw_ptr_interrupt -= runtime->boundary;
  	}
  	runtime->hw_ptr_base = hw_base;
  	runtime->status->hw_ptr = new_hw_ptr;
  	runtime->hw_ptr_jiffies = curr_jiffies;
  	if (crossed_boundary) {
  		snd_BUG_ON(crossed_boundary != 1);
  		runtime->hw_ptr_wrap += runtime->boundary;
  	}
  
  	update_audio_tstamp(substream, &curr_tstamp, &audio_tstamp);
  
  	return snd_pcm_update_state(substream, runtime);
  }
  
  /* CAUTION: call it with irq disabled */
  int snd_pcm_update_hw_ptr(struct snd_pcm_substream *substream)
  {
  	return snd_pcm_update_hw_ptr0(substream, 0);
  }
  
  /**
   * snd_pcm_set_ops - set the PCM operators
   * @pcm: the pcm instance
   * @direction: stream direction, SNDRV_PCM_STREAM_XXX
   * @ops: the operator table
   *
   * Sets the given PCM operators to the pcm instance.
   */
  void snd_pcm_set_ops(struct snd_pcm *pcm, int direction,
  		     const struct snd_pcm_ops *ops)
  {
  	struct snd_pcm_str *stream = &pcm->streams[direction];
  	struct snd_pcm_substream *substream;
  	
  	for (substream = stream->substream; substream != NULL; substream = substream->next)
  		substream->ops = ops;
  }
  EXPORT_SYMBOL(snd_pcm_set_ops);
  
  /**
   * snd_pcm_set_sync - set the PCM sync id
   * @substream: the pcm substream
   *
   * Sets the PCM sync identifier for the card.
   */
  void snd_pcm_set_sync(struct snd_pcm_substream *substream)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	
  	runtime->sync.id32[0] = substream->pcm->card->number;
  	runtime->sync.id32[1] = -1;
  	runtime->sync.id32[2] = -1;
  	runtime->sync.id32[3] = -1;
  }
  EXPORT_SYMBOL(snd_pcm_set_sync);
  
  /*
   *  Standard ioctl routine
   */
  
  static inline unsigned int div32(unsigned int a, unsigned int b, 
  				 unsigned int *r)
  {
  	if (b == 0) {
  		*r = 0;
  		return UINT_MAX;
  	}
  	*r = a % b;
  	return a / b;
  }
  
  static inline unsigned int div_down(unsigned int a, unsigned int b)
  {
  	if (b == 0)
  		return UINT_MAX;
  	return a / b;
  }
  
  static inline unsigned int div_up(unsigned int a, unsigned int b)
  {
  	unsigned int r;
  	unsigned int q;
  	if (b == 0)
  		return UINT_MAX;
  	q = div32(a, b, &r);
  	if (r)
  		++q;
  	return q;
  }
  
  static inline unsigned int mul(unsigned int a, unsigned int b)
  {
  	if (a == 0)
  		return 0;
  	if (div_down(UINT_MAX, a) < b)
  		return UINT_MAX;
  	return a * b;
  }
  
  static inline unsigned int muldiv32(unsigned int a, unsigned int b,
  				    unsigned int c, unsigned int *r)
  {
  	u_int64_t n = (u_int64_t) a * b;
  	if (c == 0) {
  		*r = 0;
  		return UINT_MAX;
  	}
  	n = div_u64_rem(n, c, r);
  	if (n >= UINT_MAX) {
  		*r = 0;
  		return UINT_MAX;
  	}
  	return n;
  }
  
  /**
   * snd_interval_refine - refine the interval value of configurator
   * @i: the interval value to refine
   * @v: the interval value to refer to
   *
   * Refines the interval value with the reference value.
   * The interval is changed to the range satisfying both intervals.
   * The interval status (min, max, integer, etc.) are evaluated.
   *
   * Return: Positive if the value is changed, zero if it's not changed, or a
   * negative error code.
   */
  int snd_interval_refine(struct snd_interval *i, const struct snd_interval *v)
  {
  	int changed = 0;
  	if (snd_BUG_ON(snd_interval_empty(i)))
  		return -EINVAL;
  	if (i->min < v->min) {
  		i->min = v->min;
  		i->openmin = v->openmin;
  		changed = 1;
  	} else if (i->min == v->min && !i->openmin && v->openmin) {
  		i->openmin = 1;
  		changed = 1;
  	}
  	if (i->max > v->max) {
  		i->max = v->max;
  		i->openmax = v->openmax;
  		changed = 1;
  	} else if (i->max == v->max && !i->openmax && v->openmax) {
  		i->openmax = 1;
  		changed = 1;
  	}
  	if (!i->integer && v->integer) {
  		i->integer = 1;
  		changed = 1;
  	}
  	if (i->integer) {
  		if (i->openmin) {
  			i->min++;
  			i->openmin = 0;
  		}
  		if (i->openmax) {
  			i->max--;
  			i->openmax = 0;
  		}
  	} else if (!i->openmin && !i->openmax && i->min == i->max)
  		i->integer = 1;
  	if (snd_interval_checkempty(i)) {
  		snd_interval_none(i);
  		return -EINVAL;
  	}
  	return changed;
  }
  EXPORT_SYMBOL(snd_interval_refine);
  
  static int snd_interval_refine_first(struct snd_interval *i)
  {
  	const unsigned int last_max = i->max;
  
  	if (snd_BUG_ON(snd_interval_empty(i)))
  		return -EINVAL;
  	if (snd_interval_single(i))
  		return 0;
  	i->max = i->min;
  	if (i->openmin)
  		i->max++;
  	/* only exclude max value if also excluded before refine */
  	i->openmax = (i->openmax && i->max >= last_max);
  	return 1;
  }
  
  static int snd_interval_refine_last(struct snd_interval *i)
  {
  	const unsigned int last_min = i->min;
  
  	if (snd_BUG_ON(snd_interval_empty(i)))
  		return -EINVAL;
  	if (snd_interval_single(i))
  		return 0;
  	i->min = i->max;
  	if (i->openmax)
  		i->min--;
  	/* only exclude min value if also excluded before refine */
  	i->openmin = (i->openmin && i->min <= last_min);
  	return 1;
  }
  
  void snd_interval_mul(const struct snd_interval *a, const struct snd_interval *b, struct snd_interval *c)
  {
  	if (a->empty || b->empty) {
  		snd_interval_none(c);
  		return;
  	}
  	c->empty = 0;
  	c->min = mul(a->min, b->min);
  	c->openmin = (a->openmin || b->openmin);
  	c->max = mul(a->max,  b->max);
  	c->openmax = (a->openmax || b->openmax);
  	c->integer = (a->integer && b->integer);
  }
  
  /**
   * snd_interval_div - refine the interval value with division
   * @a: dividend
   * @b: divisor
   * @c: quotient
   *
   * c = a / b
   *
   * Returns non-zero if the value is changed, zero if not changed.
   */
  void snd_interval_div(const struct snd_interval *a, const struct snd_interval *b, struct snd_interval *c)
  {
  	unsigned int r;
  	if (a->empty || b->empty) {
  		snd_interval_none(c);
  		return;
  	}
  	c->empty = 0;
  	c->min = div32(a->min, b->max, &r);
  	c->openmin = (r || a->openmin || b->openmax);
  	if (b->min > 0) {
  		c->max = div32(a->max, b->min, &r);
  		if (r) {
  			c->max++;
  			c->openmax = 1;
  		} else
  			c->openmax = (a->openmax || b->openmin);
  	} else {
  		c->max = UINT_MAX;
  		c->openmax = 0;
  	}
  	c->integer = 0;
  }
  
  /**
   * snd_interval_muldivk - refine the interval value
   * @a: dividend 1
   * @b: dividend 2
   * @k: divisor (as integer)
   * @c: result
    *
   * c = a * b / k
   *
   * Returns non-zero if the value is changed, zero if not changed.
   */
  void snd_interval_muldivk(const struct snd_interval *a, const struct snd_interval *b,
  		      unsigned int k, struct snd_interval *c)
  {
  	unsigned int r;
  	if (a->empty || b->empty) {
  		snd_interval_none(c);
  		return;
  	}
  	c->empty = 0;
  	c->min = muldiv32(a->min, b->min, k, &r);
  	c->openmin = (r || a->openmin || b->openmin);
  	c->max = muldiv32(a->max, b->max, k, &r);
  	if (r) {
  		c->max++;
  		c->openmax = 1;
  	} else
  		c->openmax = (a->openmax || b->openmax);
  	c->integer = 0;
  }
  
  /**
   * snd_interval_mulkdiv - refine the interval value
   * @a: dividend 1
   * @k: dividend 2 (as integer)
   * @b: divisor
   * @c: result
   *
   * c = a * k / b
   *
   * Returns non-zero if the value is changed, zero if not changed.
   */
  void snd_interval_mulkdiv(const struct snd_interval *a, unsigned int k,
  		      const struct snd_interval *b, struct snd_interval *c)
  {
  	unsigned int r;
  	if (a->empty || b->empty) {
  		snd_interval_none(c);
  		return;
  	}
  	c->empty = 0;
  	c->min = muldiv32(a->min, k, b->max, &r);
  	c->openmin = (r || a->openmin || b->openmax);
  	if (b->min > 0) {
  		c->max = muldiv32(a->max, k, b->min, &r);
  		if (r) {
  			c->max++;
  			c->openmax = 1;
  		} else
  			c->openmax = (a->openmax || b->openmin);
  	} else {
  		c->max = UINT_MAX;
  		c->openmax = 0;
  	}
  	c->integer = 0;
  }
  
  /* ---- */
  
  
  /**
   * snd_interval_ratnum - refine the interval value
   * @i: interval to refine
   * @rats_count: number of ratnum_t 
   * @rats: ratnum_t array
   * @nump: pointer to store the resultant numerator
   * @denp: pointer to store the resultant denominator
   *
   * Return: Positive if the value is changed, zero if it's not changed, or a
   * negative error code.
   */
  int snd_interval_ratnum(struct snd_interval *i,
  			unsigned int rats_count, const struct snd_ratnum *rats,
  			unsigned int *nump, unsigned int *denp)
  {
  	unsigned int best_num, best_den;
  	int best_diff;
  	unsigned int k;
  	struct snd_interval t;
  	int err;
  	unsigned int result_num, result_den;
  	int result_diff;
  
  	best_num = best_den = best_diff = 0;
  	for (k = 0; k < rats_count; ++k) {
  		unsigned int num = rats[k].num;
  		unsigned int den;
  		unsigned int q = i->min;
  		int diff;
  		if (q == 0)
  			q = 1;
  		den = div_up(num, q);
  		if (den < rats[k].den_min)
  			continue;
  		if (den > rats[k].den_max)
  			den = rats[k].den_max;
  		else {
  			unsigned int r;
  			r = (den - rats[k].den_min) % rats[k].den_step;
  			if (r != 0)
  				den -= r;
  		}
  		diff = num - q * den;
  		if (diff < 0)
  			diff = -diff;
  		if (best_num == 0 ||
  		    diff * best_den < best_diff * den) {
  			best_diff = diff;
  			best_den = den;
  			best_num = num;
  		}
  	}
  	if (best_den == 0) {
  		i->empty = 1;
  		return -EINVAL;
  	}
  	t.min = div_down(best_num, best_den);
  	t.openmin = !!(best_num % best_den);
  	
  	result_num = best_num;
  	result_diff = best_diff;
  	result_den = best_den;
  	best_num = best_den = best_diff = 0;
  	for (k = 0; k < rats_count; ++k) {
  		unsigned int num = rats[k].num;
  		unsigned int den;
  		unsigned int q = i->max;
  		int diff;
  		if (q == 0) {
  			i->empty = 1;
  			return -EINVAL;
  		}
  		den = div_down(num, q);
  		if (den > rats[k].den_max)
  			continue;
  		if (den < rats[k].den_min)
  			den = rats[k].den_min;
  		else {
  			unsigned int r;
  			r = (den - rats[k].den_min) % rats[k].den_step;
  			if (r != 0)
  				den += rats[k].den_step - r;
  		}
  		diff = q * den - num;
  		if (diff < 0)
  			diff = -diff;
  		if (best_num == 0 ||
  		    diff * best_den < best_diff * den) {
  			best_diff = diff;
  			best_den = den;
  			best_num = num;
  		}
  	}
  	if (best_den == 0) {
  		i->empty = 1;
  		return -EINVAL;
  	}
  	t.max = div_up(best_num, best_den);
  	t.openmax = !!(best_num % best_den);
  	t.integer = 0;
  	err = snd_interval_refine(i, &t);
  	if (err < 0)
  		return err;
  
  	if (snd_interval_single(i)) {
  		if (best_diff * result_den < result_diff * best_den) {
  			result_num = best_num;
  			result_den = best_den;
  		}
  		if (nump)
  			*nump = result_num;
  		if (denp)
  			*denp = result_den;
  	}
  	return err;
  }
  EXPORT_SYMBOL(snd_interval_ratnum);
  
  /**
   * snd_interval_ratden - refine the interval value
   * @i: interval to refine
   * @rats_count: number of struct ratden
   * @rats: struct ratden array
   * @nump: pointer to store the resultant numerator
   * @denp: pointer to store the resultant denominator
   *
   * Return: Positive if the value is changed, zero if it's not changed, or a
   * negative error code.
   */
  static int snd_interval_ratden(struct snd_interval *i,
  			       unsigned int rats_count,
  			       const struct snd_ratden *rats,
  			       unsigned int *nump, unsigned int *denp)
  {
  	unsigned int best_num, best_diff, best_den;
  	unsigned int k;
  	struct snd_interval t;
  	int err;
  
  	best_num = best_den = best_diff = 0;
  	for (k = 0; k < rats_count; ++k) {
  		unsigned int num;
  		unsigned int den = rats[k].den;
  		unsigned int q = i->min;
  		int diff;
  		num = mul(q, den);
  		if (num > rats[k].num_max)
  			continue;
  		if (num < rats[k].num_min)
  			num = rats[k].num_max;
  		else {
  			unsigned int r;
  			r = (num - rats[k].num_min) % rats[k].num_step;
  			if (r != 0)
  				num += rats[k].num_step - r;
  		}
  		diff = num - q * den;
  		if (best_num == 0 ||
  		    diff * best_den < best_diff * den) {
  			best_diff = diff;
  			best_den = den;
  			best_num = num;
  		}
  	}
  	if (best_den == 0) {
  		i->empty = 1;
  		return -EINVAL;
  	}
  	t.min = div_down(best_num, best_den);
  	t.openmin = !!(best_num % best_den);
  	
  	best_num = best_den = best_diff = 0;
  	for (k = 0; k < rats_count; ++k) {
  		unsigned int num;
  		unsigned int den = rats[k].den;
  		unsigned int q = i->max;
  		int diff;
  		num = mul(q, den);
  		if (num < rats[k].num_min)
  			continue;
  		if (num > rats[k].num_max)
  			num = rats[k].num_max;
  		else {
  			unsigned int r;
  			r = (num - rats[k].num_min) % rats[k].num_step;
  			if (r != 0)
  				num -= r;
  		}
  		diff = q * den - num;
  		if (best_num == 0 ||
  		    diff * best_den < best_diff * den) {
  			best_diff = diff;
  			best_den = den;
  			best_num = num;
  		}
  	}
  	if (best_den == 0) {
  		i->empty = 1;
  		return -EINVAL;
  	}
  	t.max = div_up(best_num, best_den);
  	t.openmax = !!(best_num % best_den);
  	t.integer = 0;
  	err = snd_interval_refine(i, &t);
  	if (err < 0)
  		return err;
  
  	if (snd_interval_single(i)) {
  		if (nump)
  			*nump = best_num;
  		if (denp)
  			*denp = best_den;
  	}
  	return err;
  }
  
  /**
   * snd_interval_list - refine the interval value from the list
   * @i: the interval value to refine
   * @count: the number of elements in the list
   * @list: the value list
   * @mask: the bit-mask to evaluate
   *
   * Refines the interval value from the list.
   * When mask is non-zero, only the elements corresponding to bit 1 are
   * evaluated.
   *
   * Return: Positive if the value is changed, zero if it's not changed, or a
   * negative error code.
   */
  int snd_interval_list(struct snd_interval *i, unsigned int count,
  		      const unsigned int *list, unsigned int mask)
  {
          unsigned int k;
  	struct snd_interval list_range;
  
  	if (!count) {
  		i->empty = 1;
  		return -EINVAL;
  	}
  	snd_interval_any(&list_range);
  	list_range.min = UINT_MAX;
  	list_range.max = 0;
          for (k = 0; k < count; k++) {
  		if (mask && !(mask & (1 << k)))
  			continue;
  		if (!snd_interval_test(i, list[k]))
  			continue;
  		list_range.min = min(list_range.min, list[k]);
  		list_range.max = max(list_range.max, list[k]);
          }
  	return snd_interval_refine(i, &list_range);
  }
  EXPORT_SYMBOL(snd_interval_list);
  
  /**
   * snd_interval_ranges - refine the interval value from the list of ranges
   * @i: the interval value to refine
   * @count: the number of elements in the list of ranges
   * @ranges: the ranges list
   * @mask: the bit-mask to evaluate
   *
   * Refines the interval value from the list of ranges.
   * When mask is non-zero, only the elements corresponding to bit 1 are
   * evaluated.
   *
   * Return: Positive if the value is changed, zero if it's not changed, or a
   * negative error code.
   */
  int snd_interval_ranges(struct snd_interval *i, unsigned int count,
  			const struct snd_interval *ranges, unsigned int mask)
  {
  	unsigned int k;
  	struct snd_interval range_union;
  	struct snd_interval range;
  
  	if (!count) {
  		snd_interval_none(i);
  		return -EINVAL;
  	}
  	snd_interval_any(&range_union);
  	range_union.min = UINT_MAX;
  	range_union.max = 0;
  	for (k = 0; k < count; k++) {
  		if (mask && !(mask & (1 << k)))
  			continue;
  		snd_interval_copy(&range, &ranges[k]);
  		if (snd_interval_refine(&range, i) < 0)
  			continue;
  		if (snd_interval_empty(&range))
  			continue;
  
  		if (range.min < range_union.min) {
  			range_union.min = range.min;
  			range_union.openmin = 1;
  		}
  		if (range.min == range_union.min && !range.openmin)
  			range_union.openmin = 0;
  		if (range.max > range_union.max) {
  			range_union.max = range.max;
  			range_union.openmax = 1;
  		}
  		if (range.max == range_union.max && !range.openmax)
  			range_union.openmax = 0;
  	}
  	return snd_interval_refine(i, &range_union);
  }
  EXPORT_SYMBOL(snd_interval_ranges);
  
  static int snd_interval_step(struct snd_interval *i, unsigned int step)
  {
  	unsigned int n;
  	int changed = 0;
  	n = i->min % step;
  	if (n != 0 || i->openmin) {
  		i->min += step - n;
  		i->openmin = 0;
  		changed = 1;
  	}
  	n = i->max % step;
  	if (n != 0 || i->openmax) {
  		i->max -= n;
  		i->openmax = 0;
  		changed = 1;
  	}
  	if (snd_interval_checkempty(i)) {
  		i->empty = 1;
  		return -EINVAL;
  	}
  	return changed;
  }
  
  /* Info constraints helpers */
  
  /**
   * snd_pcm_hw_rule_add - add the hw-constraint rule
   * @runtime: the pcm runtime instance
   * @cond: condition bits
   * @var: the variable to evaluate
   * @func: the evaluation function
   * @private: the private data pointer passed to function
   * @dep: the dependent variables
   *
   * Return: Zero if successful, or a negative error code on failure.
   */
  int snd_pcm_hw_rule_add(struct snd_pcm_runtime *runtime, unsigned int cond,
  			int var,
  			snd_pcm_hw_rule_func_t func, void *private,
  			int dep, ...)
  {
  	struct snd_pcm_hw_constraints *constrs = &runtime->hw_constraints;
  	struct snd_pcm_hw_rule *c;
  	unsigned int k;
  	va_list args;
  	va_start(args, dep);
  	if (constrs->rules_num >= constrs->rules_all) {
  		struct snd_pcm_hw_rule *new;
  		unsigned int new_rules = constrs->rules_all + 16;
  		new = krealloc_array(constrs->rules, new_rules,
  				     sizeof(*c), GFP_KERNEL);
  		if (!new) {
  			va_end(args);
  			return -ENOMEM;
  		}
  		constrs->rules = new;
  		constrs->rules_all = new_rules;
  	}
  	c = &constrs->rules[constrs->rules_num];
  	c->cond = cond;
  	c->func = func;
  	c->var = var;
  	c->private = private;
  	k = 0;
  	while (1) {
  		if (snd_BUG_ON(k >= ARRAY_SIZE(c->deps))) {
  			va_end(args);
  			return -EINVAL;
  		}
  		c->deps[k++] = dep;
  		if (dep < 0)
  			break;
  		dep = va_arg(args, int);
  	}
  	constrs->rules_num++;
  	va_end(args);
  	return 0;
  }
  EXPORT_SYMBOL(snd_pcm_hw_rule_add);
  
  /**
   * snd_pcm_hw_constraint_mask - apply the given bitmap mask constraint
   * @runtime: PCM runtime instance
   * @var: hw_params variable to apply the mask
   * @mask: the bitmap mask
   *
   * Apply the constraint of the given bitmap mask to a 32-bit mask parameter.
   *
   * Return: Zero if successful, or a negative error code on failure.
   */
  int snd_pcm_hw_constraint_mask(struct snd_pcm_runtime *runtime, snd_pcm_hw_param_t var,
  			       u_int32_t mask)
  {
  	struct snd_pcm_hw_constraints *constrs = &runtime->hw_constraints;
  	struct snd_mask *maskp = constrs_mask(constrs, var);
  	*maskp->bits &= mask;
  	memset(maskp->bits + 1, 0, (SNDRV_MASK_MAX-32) / 8); /* clear rest */
  	if (*maskp->bits == 0)
  		return -EINVAL;
  	return 0;
  }
  
  /**
   * snd_pcm_hw_constraint_mask64 - apply the given bitmap mask constraint
   * @runtime: PCM runtime instance
   * @var: hw_params variable to apply the mask
   * @mask: the 64bit bitmap mask
   *
   * Apply the constraint of the given bitmap mask to a 64-bit mask parameter.
   *
   * Return: Zero if successful, or a negative error code on failure.
   */
  int snd_pcm_hw_constraint_mask64(struct snd_pcm_runtime *runtime, snd_pcm_hw_param_t var,
  				 u_int64_t mask)
  {
  	struct snd_pcm_hw_constraints *constrs = &runtime->hw_constraints;
  	struct snd_mask *maskp = constrs_mask(constrs, var);
  	maskp->bits[0] &= (u_int32_t)mask;
  	maskp->bits[1] &= (u_int32_t)(mask >> 32);
  	memset(maskp->bits + 2, 0, (SNDRV_MASK_MAX-64) / 8); /* clear rest */
  	if (! maskp->bits[0] && ! maskp->bits[1])
  		return -EINVAL;
  	return 0;
  }
  EXPORT_SYMBOL(snd_pcm_hw_constraint_mask64);
  
  /**
   * snd_pcm_hw_constraint_integer - apply an integer constraint to an interval
   * @runtime: PCM runtime instance
   * @var: hw_params variable to apply the integer constraint
   *
   * Apply the constraint of integer to an interval parameter.
   *
   * Return: Positive if the value is changed, zero if it's not changed, or a
   * negative error code.
   */
  int snd_pcm_hw_constraint_integer(struct snd_pcm_runtime *runtime, snd_pcm_hw_param_t var)
  {
  	struct snd_pcm_hw_constraints *constrs = &runtime->hw_constraints;
  	return snd_interval_setinteger(constrs_interval(constrs, var));
  }
  EXPORT_SYMBOL(snd_pcm_hw_constraint_integer);
  
  /**
   * snd_pcm_hw_constraint_minmax - apply a min/max range constraint to an interval
   * @runtime: PCM runtime instance
   * @var: hw_params variable to apply the range
   * @min: the minimal value
   * @max: the maximal value
   * 
   * Apply the min/max range constraint to an interval parameter.
   *
   * Return: Positive if the value is changed, zero if it's not changed, or a
   * negative error code.
   */
  int snd_pcm_hw_constraint_minmax(struct snd_pcm_runtime *runtime, snd_pcm_hw_param_t var,
  				 unsigned int min, unsigned int max)
  {
  	struct snd_pcm_hw_constraints *constrs = &runtime->hw_constraints;
  	struct snd_interval t;
  	t.min = min;
  	t.max = max;
  	t.openmin = t.openmax = 0;
  	t.integer = 0;
  	return snd_interval_refine(constrs_interval(constrs, var), &t);
  }
  EXPORT_SYMBOL(snd_pcm_hw_constraint_minmax);
  
  static int snd_pcm_hw_rule_list(struct snd_pcm_hw_params *params,
  				struct snd_pcm_hw_rule *rule)
  {
  	struct snd_pcm_hw_constraint_list *list = rule->private;
  	return snd_interval_list(hw_param_interval(params, rule->var), list->count, list->list, list->mask);
  }		
  
  
  /**
   * snd_pcm_hw_constraint_list - apply a list of constraints to a parameter
   * @runtime: PCM runtime instance
   * @cond: condition bits
   * @var: hw_params variable to apply the list constraint
   * @l: list
   * 
   * Apply the list of constraints to an interval parameter.
   *
   * Return: Zero if successful, or a negative error code on failure.
   */
  int snd_pcm_hw_constraint_list(struct snd_pcm_runtime *runtime,
  			       unsigned int cond,
  			       snd_pcm_hw_param_t var,
  			       const struct snd_pcm_hw_constraint_list *l)
  {
  	return snd_pcm_hw_rule_add(runtime, cond, var,
  				   snd_pcm_hw_rule_list, (void *)l,
  				   var, -1);
  }
  EXPORT_SYMBOL(snd_pcm_hw_constraint_list);
  
  static int snd_pcm_hw_rule_ranges(struct snd_pcm_hw_params *params,
  				  struct snd_pcm_hw_rule *rule)
  {
  	struct snd_pcm_hw_constraint_ranges *r = rule->private;
  	return snd_interval_ranges(hw_param_interval(params, rule->var),
  				   r->count, r->ranges, r->mask);
  }
  
  
  /**
   * snd_pcm_hw_constraint_ranges - apply list of range constraints to a parameter
   * @runtime: PCM runtime instance
   * @cond: condition bits
   * @var: hw_params variable to apply the list of range constraints
   * @r: ranges
   *
   * Apply the list of range constraints to an interval parameter.
   *
   * Return: Zero if successful, or a negative error code on failure.
   */
  int snd_pcm_hw_constraint_ranges(struct snd_pcm_runtime *runtime,
  				 unsigned int cond,
  				 snd_pcm_hw_param_t var,
  				 const struct snd_pcm_hw_constraint_ranges *r)
  {
  	return snd_pcm_hw_rule_add(runtime, cond, var,
  				   snd_pcm_hw_rule_ranges, (void *)r,
  				   var, -1);
  }
  EXPORT_SYMBOL(snd_pcm_hw_constraint_ranges);
  
  static int snd_pcm_hw_rule_ratnums(struct snd_pcm_hw_params *params,
  				   struct snd_pcm_hw_rule *rule)
  {
  	const struct snd_pcm_hw_constraint_ratnums *r = rule->private;
  	unsigned int num = 0, den = 0;
  	int err;
  	err = snd_interval_ratnum(hw_param_interval(params, rule->var),
  				  r->nrats, r->rats, &num, &den);
  	if (err >= 0 && den && rule->var == SNDRV_PCM_HW_PARAM_RATE) {
  		params->rate_num = num;
  		params->rate_den = den;
  	}
  	return err;
  }
  
  /**
   * snd_pcm_hw_constraint_ratnums - apply ratnums constraint to a parameter
   * @runtime: PCM runtime instance
   * @cond: condition bits
   * @var: hw_params variable to apply the ratnums constraint
   * @r: struct snd_ratnums constriants
   *
   * Return: Zero if successful, or a negative error code on failure.
   */
  int snd_pcm_hw_constraint_ratnums(struct snd_pcm_runtime *runtime, 
  				  unsigned int cond,
  				  snd_pcm_hw_param_t var,
  				  const struct snd_pcm_hw_constraint_ratnums *r)
  {
  	return snd_pcm_hw_rule_add(runtime, cond, var,
  				   snd_pcm_hw_rule_ratnums, (void *)r,
  				   var, -1);
  }
  EXPORT_SYMBOL(snd_pcm_hw_constraint_ratnums);
  
  static int snd_pcm_hw_rule_ratdens(struct snd_pcm_hw_params *params,
  				   struct snd_pcm_hw_rule *rule)
  {
  	const struct snd_pcm_hw_constraint_ratdens *r = rule->private;
  	unsigned int num = 0, den = 0;
  	int err = snd_interval_ratden(hw_param_interval(params, rule->var),
  				  r->nrats, r->rats, &num, &den);
  	if (err >= 0 && den && rule->var == SNDRV_PCM_HW_PARAM_RATE) {
  		params->rate_num = num;
  		params->rate_den = den;
  	}
  	return err;
  }
  
  /**
   * snd_pcm_hw_constraint_ratdens - apply ratdens constraint to a parameter
   * @runtime: PCM runtime instance
   * @cond: condition bits
   * @var: hw_params variable to apply the ratdens constraint
   * @r: struct snd_ratdens constriants
   *
   * Return: Zero if successful, or a negative error code on failure.
   */
  int snd_pcm_hw_constraint_ratdens(struct snd_pcm_runtime *runtime, 
  				  unsigned int cond,
  				  snd_pcm_hw_param_t var,
  				  const struct snd_pcm_hw_constraint_ratdens *r)
  {
  	return snd_pcm_hw_rule_add(runtime, cond, var,
  				   snd_pcm_hw_rule_ratdens, (void *)r,
  				   var, -1);
  }
  EXPORT_SYMBOL(snd_pcm_hw_constraint_ratdens);
  
  static int snd_pcm_hw_rule_msbits(struct snd_pcm_hw_params *params,
  				  struct snd_pcm_hw_rule *rule)
  {
  	unsigned int l = (unsigned long) rule->private;
  	int width = l & 0xffff;
  	unsigned int msbits = l >> 16;
  	const struct snd_interval *i =
  		hw_param_interval_c(params, SNDRV_PCM_HW_PARAM_SAMPLE_BITS);
  
  	if (!snd_interval_single(i))
  		return 0;
  
  	if ((snd_interval_value(i) == width) ||
  	    (width == 0 && snd_interval_value(i) > msbits))
  		params->msbits = min_not_zero(params->msbits, msbits);
  
  	return 0;
  }
  
  /**
   * snd_pcm_hw_constraint_msbits - add a hw constraint msbits rule
   * @runtime: PCM runtime instance
   * @cond: condition bits
   * @width: sample bits width
   * @msbits: msbits width
   *
   * This constraint will set the number of most significant bits (msbits) if a
   * sample format with the specified width has been select. If width is set to 0
   * the msbits will be set for any sample format with a width larger than the
   * specified msbits.
   *
   * Return: Zero if successful, or a negative error code on failure.
   */
  int snd_pcm_hw_constraint_msbits(struct snd_pcm_runtime *runtime, 
  				 unsigned int cond,
  				 unsigned int width,
  				 unsigned int msbits)
  {
  	unsigned long l = (msbits << 16) | width;
  	return snd_pcm_hw_rule_add(runtime, cond, -1,
  				    snd_pcm_hw_rule_msbits,
  				    (void*) l,
  				    SNDRV_PCM_HW_PARAM_SAMPLE_BITS, -1);
  }
  EXPORT_SYMBOL(snd_pcm_hw_constraint_msbits);
  
  static int snd_pcm_hw_rule_step(struct snd_pcm_hw_params *params,
  				struct snd_pcm_hw_rule *rule)
  {
  	unsigned long step = (unsigned long) rule->private;
  	return snd_interval_step(hw_param_interval(params, rule->var), step);
  }
  
  /**
   * snd_pcm_hw_constraint_step - add a hw constraint step rule
   * @runtime: PCM runtime instance
   * @cond: condition bits
   * @var: hw_params variable to apply the step constraint
   * @step: step size
   *
   * Return: Zero if successful, or a negative error code on failure.
   */
  int snd_pcm_hw_constraint_step(struct snd_pcm_runtime *runtime,
  			       unsigned int cond,
  			       snd_pcm_hw_param_t var,
  			       unsigned long step)
  {
  	return snd_pcm_hw_rule_add(runtime, cond, var, 
  				   snd_pcm_hw_rule_step, (void *) step,
  				   var, -1);
  }
  EXPORT_SYMBOL(snd_pcm_hw_constraint_step);
  
  static int snd_pcm_hw_rule_pow2(struct snd_pcm_hw_params *params, struct snd_pcm_hw_rule *rule)
  {
  	static const unsigned int pow2_sizes[] = {
  		1<<0, 1<<1, 1<<2, 1<<3, 1<<4, 1<<5, 1<<6, 1<<7,
  		1<<8, 1<<9, 1<<10, 1<<11, 1<<12, 1<<13, 1<<14, 1<<15,
  		1<<16, 1<<17, 1<<18, 1<<19, 1<<20, 1<<21, 1<<22, 1<<23,
  		1<<24, 1<<25, 1<<26, 1<<27, 1<<28, 1<<29, 1<<30
  	};
  	return snd_interval_list(hw_param_interval(params, rule->var),
  				 ARRAY_SIZE(pow2_sizes), pow2_sizes, 0);
  }		
  
  /**
   * snd_pcm_hw_constraint_pow2 - add a hw constraint power-of-2 rule
   * @runtime: PCM runtime instance
   * @cond: condition bits
   * @var: hw_params variable to apply the power-of-2 constraint
   *
   * Return: Zero if successful, or a negative error code on failure.
   */
  int snd_pcm_hw_constraint_pow2(struct snd_pcm_runtime *runtime,
  			       unsigned int cond,
  			       snd_pcm_hw_param_t var)
  {
  	return snd_pcm_hw_rule_add(runtime, cond, var, 
  				   snd_pcm_hw_rule_pow2, NULL,
  				   var, -1);
  }
  EXPORT_SYMBOL(snd_pcm_hw_constraint_pow2);
  
  static int snd_pcm_hw_rule_noresample_func(struct snd_pcm_hw_params *params,
  					   struct snd_pcm_hw_rule *rule)
  {
  	unsigned int base_rate = (unsigned int)(uintptr_t)rule->private;
  	struct snd_interval *rate;
  
  	rate = hw_param_interval(params, SNDRV_PCM_HW_PARAM_RATE);
  	return snd_interval_list(rate, 1, &base_rate, 0);
  }
  
  /**
   * snd_pcm_hw_rule_noresample - add a rule to allow disabling hw resampling
   * @runtime: PCM runtime instance
   * @base_rate: the rate at which the hardware does not resample
   *
   * Return: Zero if successful, or a negative error code on failure.
   */
  int snd_pcm_hw_rule_noresample(struct snd_pcm_runtime *runtime,
  			       unsigned int base_rate)
  {
  	return snd_pcm_hw_rule_add(runtime, SNDRV_PCM_HW_PARAMS_NORESAMPLE,
  				   SNDRV_PCM_HW_PARAM_RATE,
  				   snd_pcm_hw_rule_noresample_func,
  				   (void *)(uintptr_t)base_rate,
  				   SNDRV_PCM_HW_PARAM_RATE, -1);
  }
  EXPORT_SYMBOL(snd_pcm_hw_rule_noresample);
  
  static void _snd_pcm_hw_param_any(struct snd_pcm_hw_params *params,
  				  snd_pcm_hw_param_t var)
  {
  	if (hw_is_mask(var)) {
  		snd_mask_any(hw_param_mask(params, var));
  		params->cmask |= 1 << var;
  		params->rmask |= 1 << var;
  		return;
  	}
  	if (hw_is_interval(var)) {
  		snd_interval_any(hw_param_interval(params, var));
  		params->cmask |= 1 << var;
  		params->rmask |= 1 << var;
  		return;
  	}
  	snd_BUG();
  }
  
  void _snd_pcm_hw_params_any(struct snd_pcm_hw_params *params)
  {
  	unsigned int k;
  	memset(params, 0, sizeof(*params));
  	for (k = SNDRV_PCM_HW_PARAM_FIRST_MASK; k <= SNDRV_PCM_HW_PARAM_LAST_MASK; k++)
  		_snd_pcm_hw_param_any(params, k);
  	for (k = SNDRV_PCM_HW_PARAM_FIRST_INTERVAL; k <= SNDRV_PCM_HW_PARAM_LAST_INTERVAL; k++)
  		_snd_pcm_hw_param_any(params, k);
  	params->info = ~0U;
  }
  EXPORT_SYMBOL(_snd_pcm_hw_params_any);
  
  /**
   * snd_pcm_hw_param_value - return @params field @var value
   * @params: the hw_params instance
   * @var: parameter to retrieve
   * @dir: pointer to the direction (-1,0,1) or %NULL
   *
   * Return: The value for field @var if it's fixed in configuration space
   * defined by @params. -%EINVAL otherwise.
   */
  int snd_pcm_hw_param_value(const struct snd_pcm_hw_params *params,
  			   snd_pcm_hw_param_t var, int *dir)
  {
  	if (hw_is_mask(var)) {
  		const struct snd_mask *mask = hw_param_mask_c(params, var);
  		if (!snd_mask_single(mask))
  			return -EINVAL;
  		if (dir)
  			*dir = 0;
  		return snd_mask_value(mask);
  	}
  	if (hw_is_interval(var)) {
  		const struct snd_interval *i = hw_param_interval_c(params, var);
  		if (!snd_interval_single(i))
  			return -EINVAL;
  		if (dir)
  			*dir = i->openmin;
  		return snd_interval_value(i);
  	}
  	return -EINVAL;
  }
  EXPORT_SYMBOL(snd_pcm_hw_param_value);
  
  void _snd_pcm_hw_param_setempty(struct snd_pcm_hw_params *params,
  				snd_pcm_hw_param_t var)
  {
  	if (hw_is_mask(var)) {
  		snd_mask_none(hw_param_mask(params, var));
  		params->cmask |= 1 << var;
  		params->rmask |= 1 << var;
  	} else if (hw_is_interval(var)) {
  		snd_interval_none(hw_param_interval(params, var));
  		params->cmask |= 1 << var;
  		params->rmask |= 1 << var;
  	} else {
  		snd_BUG();
  	}
  }
  EXPORT_SYMBOL(_snd_pcm_hw_param_setempty);
  
  static int _snd_pcm_hw_param_first(struct snd_pcm_hw_params *params,
  				   snd_pcm_hw_param_t var)
  {
  	int changed;
  	if (hw_is_mask(var))
  		changed = snd_mask_refine_first(hw_param_mask(params, var));
  	else if (hw_is_interval(var))
  		changed = snd_interval_refine_first(hw_param_interval(params, var));
  	else
  		return -EINVAL;
  	if (changed > 0) {
  		params->cmask |= 1 << var;
  		params->rmask |= 1 << var;
  	}
  	return changed;
  }
  
  
  /**
   * snd_pcm_hw_param_first - refine config space and return minimum value
   * @pcm: PCM instance
   * @params: the hw_params instance
   * @var: parameter to retrieve
   * @dir: pointer to the direction (-1,0,1) or %NULL
   *
   * Inside configuration space defined by @params remove from @var all
   * values > minimum. Reduce configuration space accordingly.
   *
   * Return: The minimum, or a negative error code on failure.
   */
  int snd_pcm_hw_param_first(struct snd_pcm_substream *pcm, 
  			   struct snd_pcm_hw_params *params, 
  			   snd_pcm_hw_param_t var, int *dir)
  {
  	int changed = _snd_pcm_hw_param_first(params, var);
  	if (changed < 0)
  		return changed;
  	if (params->rmask) {
  		int err = snd_pcm_hw_refine(pcm, params);
  		if (err < 0)
  			return err;
  	}
  	return snd_pcm_hw_param_value(params, var, dir);
  }
  EXPORT_SYMBOL(snd_pcm_hw_param_first);
  
  static int _snd_pcm_hw_param_last(struct snd_pcm_hw_params *params,
  				  snd_pcm_hw_param_t var)
  {
  	int changed;
  	if (hw_is_mask(var))
  		changed = snd_mask_refine_last(hw_param_mask(params, var));
  	else if (hw_is_interval(var))
  		changed = snd_interval_refine_last(hw_param_interval(params, var));
  	else
  		return -EINVAL;
  	if (changed > 0) {
  		params->cmask |= 1 << var;
  		params->rmask |= 1 << var;
  	}
  	return changed;
  }
  
  
  /**
   * snd_pcm_hw_param_last - refine config space and return maximum value
   * @pcm: PCM instance
   * @params: the hw_params instance
   * @var: parameter to retrieve
   * @dir: pointer to the direction (-1,0,1) or %NULL
   *
   * Inside configuration space defined by @params remove from @var all
   * values < maximum. Reduce configuration space accordingly.
   *
   * Return: The maximum, or a negative error code on failure.
   */
  int snd_pcm_hw_param_last(struct snd_pcm_substream *pcm, 
  			  struct snd_pcm_hw_params *params,
  			  snd_pcm_hw_param_t var, int *dir)
  {
  	int changed = _snd_pcm_hw_param_last(params, var);
  	if (changed < 0)
  		return changed;
  	if (params->rmask) {
  		int err = snd_pcm_hw_refine(pcm, params);
  		if (err < 0)
  			return err;
  	}
  	return snd_pcm_hw_param_value(params, var, dir);
  }
  EXPORT_SYMBOL(snd_pcm_hw_param_last);
  
  static int snd_pcm_lib_ioctl_reset(struct snd_pcm_substream *substream,
  				   void *arg)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	unsigned long flags;
  	snd_pcm_stream_lock_irqsave(substream, flags);
  	if (snd_pcm_running(substream) &&
  	    snd_pcm_update_hw_ptr(substream) >= 0)
  		runtime->status->hw_ptr %= runtime->buffer_size;
  	else {
  		runtime->status->hw_ptr = 0;
  		runtime->hw_ptr_wrap = 0;
  	}
  	snd_pcm_stream_unlock_irqrestore(substream, flags);
  	return 0;
  }
  
  static int snd_pcm_lib_ioctl_channel_info(struct snd_pcm_substream *substream,
  					  void *arg)
  {
  	struct snd_pcm_channel_info *info = arg;
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	int width;
  	if (!(runtime->info & SNDRV_PCM_INFO_MMAP)) {
  		info->offset = -1;
  		return 0;
  	}
  	width = snd_pcm_format_physical_width(runtime->format);
  	if (width < 0)
  		return width;
  	info->offset = 0;
  	switch (runtime->access) {
  	case SNDRV_PCM_ACCESS_MMAP_INTERLEAVED:
  	case SNDRV_PCM_ACCESS_RW_INTERLEAVED:
  		info->first = info->channel * width;
  		info->step = runtime->channels * width;
  		break;
  	case SNDRV_PCM_ACCESS_MMAP_NONINTERLEAVED:
  	case SNDRV_PCM_ACCESS_RW_NONINTERLEAVED:
  	{
  		size_t size = runtime->dma_bytes / runtime->channels;
  		info->first = info->channel * size * 8;
  		info->step = width;
  		break;
  	}
  	default:
  		snd_BUG();
  		break;
  	}
  	return 0;
  }
  
  static int snd_pcm_lib_ioctl_fifo_size(struct snd_pcm_substream *substream,
  				       void *arg)
  {
  	struct snd_pcm_hw_params *params = arg;
  	snd_pcm_format_t format;
  	int channels;
  	ssize_t frame_size;
  
  	params->fifo_size = substream->runtime->hw.fifo_size;
  	if (!(substream->runtime->hw.info & SNDRV_PCM_INFO_FIFO_IN_FRAMES)) {
  		format = params_format(params);
  		channels = params_channels(params);
  		frame_size = snd_pcm_format_size(format, channels);
  		if (frame_size > 0)
  			params->fifo_size /= (unsigned)frame_size;
  	}
  	return 0;
  }
  
  /**
   * snd_pcm_lib_ioctl - a generic PCM ioctl callback
   * @substream: the pcm substream instance
   * @cmd: ioctl command
   * @arg: ioctl argument
   *
   * Processes the generic ioctl commands for PCM.
   * Can be passed as the ioctl callback for PCM ops.
   *
   * Return: Zero if successful, or a negative error code on failure.
   */
  int snd_pcm_lib_ioctl(struct snd_pcm_substream *substream,
  		      unsigned int cmd, void *arg)
  {
  	switch (cmd) {
  	case SNDRV_PCM_IOCTL1_RESET:
  		return snd_pcm_lib_ioctl_reset(substream, arg);
  	case SNDRV_PCM_IOCTL1_CHANNEL_INFO:
  		return snd_pcm_lib_ioctl_channel_info(substream, arg);
  	case SNDRV_PCM_IOCTL1_FIFO_SIZE:
  		return snd_pcm_lib_ioctl_fifo_size(substream, arg);
  	}
  	return -ENXIO;
  }
  EXPORT_SYMBOL(snd_pcm_lib_ioctl);
  
  /**
   * snd_pcm_period_elapsed - update the pcm status for the next period
   * @substream: the pcm substream instance
   *
   * This function is called from the interrupt handler when the
   * PCM has processed the period size.  It will update the current
   * pointer, wake up sleepers, etc.
   *
   * Even if more than one periods have elapsed since the last call, you
   * have to call this only once.
   */
  void snd_pcm_period_elapsed(struct snd_pcm_substream *substream)
  {
  	struct snd_pcm_runtime *runtime;
  	unsigned long flags;
  
  	if (snd_BUG_ON(!substream))
  		return;
  
  	snd_pcm_stream_lock_irqsave(substream, flags);
  	if (PCM_RUNTIME_CHECK(substream))
  		goto _unlock;
  	runtime = substream->runtime;
  
  	if (!snd_pcm_running(substream) ||
  	    snd_pcm_update_hw_ptr0(substream, 1) < 0)
  		goto _end;
  
  #ifdef CONFIG_SND_PCM_TIMER
  	if (substream->timer_running)
  		snd_timer_interrupt(substream->timer, 1);
  #endif
   _end:
  	kill_fasync(&runtime->fasync, SIGIO, POLL_IN);
   _unlock:
  	snd_pcm_stream_unlock_irqrestore(substream, flags);
  }
  EXPORT_SYMBOL(snd_pcm_period_elapsed);
  
  /*
   * Wait until avail_min data becomes available
   * Returns a negative error code if any error occurs during operation.
   * The available space is stored on availp.  When err = 0 and avail = 0
   * on the capture stream, it indicates the stream is in DRAINING state.
   */
  static int wait_for_avail(struct snd_pcm_substream *substream,
  			      snd_pcm_uframes_t *availp)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	int is_playback = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
  	wait_queue_entry_t wait;
  	int err = 0;
  	snd_pcm_uframes_t avail = 0;
  	long wait_time, tout;
  
  	init_waitqueue_entry(&wait, current);
  	set_current_state(TASK_INTERRUPTIBLE);
  	add_wait_queue(&runtime->tsleep, &wait);
  
  	if (runtime->no_period_wakeup)
  		wait_time = MAX_SCHEDULE_TIMEOUT;
  	else {
  		/* use wait time from substream if available */
  		if (substream->wait_time) {
  			wait_time = substream->wait_time;
  		} else {
  			wait_time = 10;
  
  			if (runtime->rate) {
  				long t = runtime->period_size * 2 /
  					 runtime->rate;
  				wait_time = max(t, wait_time);
  			}
  			wait_time = msecs_to_jiffies(wait_time * 1000);
  		}
  	}
  
  	for (;;) {
  		if (signal_pending(current)) {
  			err = -ERESTARTSYS;
  			break;
  		}
  
  		/*
  		 * We need to check if space became available already
  		 * (and thus the wakeup happened already) first to close
  		 * the race of space already having become available.
  		 * This check must happen after been added to the waitqueue
  		 * and having current state be INTERRUPTIBLE.
  		 */
  		avail = snd_pcm_avail(substream);
  		if (avail >= runtime->twake)
  			break;
  		snd_pcm_stream_unlock_irq(substream);
  
  		tout = schedule_timeout(wait_time);
  
  		snd_pcm_stream_lock_irq(substream);
  		set_current_state(TASK_INTERRUPTIBLE);
  		switch (runtime->status->state) {
  		case SNDRV_PCM_STATE_SUSPENDED:
  			err = -ESTRPIPE;
  			goto _endloop;
  		case SNDRV_PCM_STATE_XRUN:
  			err = -EPIPE;
  			goto _endloop;
  		case SNDRV_PCM_STATE_DRAINING:
  			if (is_playback)
  				err = -EPIPE;
  			else 
  				avail = 0; /* indicate draining */
  			goto _endloop;
  		case SNDRV_PCM_STATE_OPEN:
  		case SNDRV_PCM_STATE_SETUP:
  		case SNDRV_PCM_STATE_DISCONNECTED:
  			err = -EBADFD;
  			goto _endloop;
  		case SNDRV_PCM_STATE_PAUSED:
  			continue;
  		}
  		if (!tout) {
  			pcm_dbg(substream->pcm,
  				"%s write error (DMA or IRQ trouble?)\n",
  				is_playback ? "playback" : "capture");
  			err = -EIO;
  			break;
  		}
  	}
   _endloop:
  	set_current_state(TASK_RUNNING);
  	remove_wait_queue(&runtime->tsleep, &wait);
  	*availp = avail;
  	return err;
  }
  	
  typedef int (*pcm_transfer_f)(struct snd_pcm_substream *substream,
  			      int channel, unsigned long hwoff,
  			      void *buf, unsigned long bytes);
  
  typedef int (*pcm_copy_f)(struct snd_pcm_substream *, snd_pcm_uframes_t, void *,
  			  snd_pcm_uframes_t, snd_pcm_uframes_t, pcm_transfer_f);
  
  /* calculate the target DMA-buffer position to be written/read */
  static void *get_dma_ptr(struct snd_pcm_runtime *runtime,
  			   int channel, unsigned long hwoff)
  {
  	return runtime->dma_area + hwoff +
  		channel * (runtime->dma_bytes / runtime->channels);
  }
  
  /* default copy_user ops for write; used for both interleaved and non- modes */
  static int default_write_copy(struct snd_pcm_substream *substream,
  			      int channel, unsigned long hwoff,
  			      void *buf, unsigned long bytes)
  {
  	if (copy_from_user(get_dma_ptr(substream->runtime, channel, hwoff),
  			   (void __user *)buf, bytes))
  		return -EFAULT;
  	return 0;
  }
  
  /* default copy_kernel ops for write */
  static int default_write_copy_kernel(struct snd_pcm_substream *substream,
  				     int channel, unsigned long hwoff,
  				     void *buf, unsigned long bytes)
  {
  	memcpy(get_dma_ptr(substream->runtime, channel, hwoff), buf, bytes);
  	return 0;
  }
  
  /* fill silence instead of copy data; called as a transfer helper
   * from __snd_pcm_lib_write() or directly from noninterleaved_copy() when
   * a NULL buffer is passed
   */
  static int fill_silence(struct snd_pcm_substream *substream, int channel,
  			unsigned long hwoff, void *buf, unsigned long bytes)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  
  	if (substream->stream != SNDRV_PCM_STREAM_PLAYBACK)
  		return 0;
  	if (substream->ops->fill_silence)
  		return substream->ops->fill_silence(substream, channel,
  						    hwoff, bytes);
  
  	snd_pcm_format_set_silence(runtime->format,
  				   get_dma_ptr(runtime, channel, hwoff),
  				   bytes_to_samples(runtime, bytes));
  	return 0;
  }
  
  /* default copy_user ops for read; used for both interleaved and non- modes */
  static int default_read_copy(struct snd_pcm_substream *substream,
  			     int channel, unsigned long hwoff,
  			     void *buf, unsigned long bytes)
  {
  	if (copy_to_user((void __user *)buf,
  			 get_dma_ptr(substream->runtime, channel, hwoff),
  			 bytes))
  		return -EFAULT;
  	return 0;
  }
  
  /* default copy_kernel ops for read */
  static int default_read_copy_kernel(struct snd_pcm_substream *substream,
  				    int channel, unsigned long hwoff,
  				    void *buf, unsigned long bytes)
  {
  	memcpy(buf, get_dma_ptr(substream->runtime, channel, hwoff), bytes);
  	return 0;
  }
  
  /* call transfer function with the converted pointers and sizes;
   * for interleaved mode, it's one shot for all samples
   */
  static int interleaved_copy(struct snd_pcm_substream *substream,
  			    snd_pcm_uframes_t hwoff, void *data,
  			    snd_pcm_uframes_t off,
  			    snd_pcm_uframes_t frames,
  			    pcm_transfer_f transfer)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  
  	/* convert to bytes */
  	hwoff = frames_to_bytes(runtime, hwoff);
  	off = frames_to_bytes(runtime, off);
  	frames = frames_to_bytes(runtime, frames);
  	return transfer(substream, 0, hwoff, data + off, frames);
  }
  
  /* call transfer function with the converted pointers and sizes for each
   * non-interleaved channel; when buffer is NULL, silencing instead of copying
   */
  static int noninterleaved_copy(struct snd_pcm_substream *substream,
  			       snd_pcm_uframes_t hwoff, void *data,
  			       snd_pcm_uframes_t off,
  			       snd_pcm_uframes_t frames,
  			       pcm_transfer_f transfer)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	int channels = runtime->channels;
  	void **bufs = data;
  	int c, err;
  
  	/* convert to bytes; note that it's not frames_to_bytes() here.
  	 * in non-interleaved mode, we copy for each channel, thus
  	 * each copy is n_samples bytes x channels = whole frames.
  	 */
  	off = samples_to_bytes(runtime, off);
  	frames = samples_to_bytes(runtime, frames);
  	hwoff = samples_to_bytes(runtime, hwoff);
  	for (c = 0; c < channels; ++c, ++bufs) {
  		if (!data || !*bufs)
  			err = fill_silence(substream, c, hwoff, NULL, frames);
  		else
  			err = transfer(substream, c, hwoff, *bufs + off,
  				       frames);
  		if (err < 0)
  			return err;
  	}
  	return 0;
  }
  
  /* fill silence on the given buffer position;
   * called from snd_pcm_playback_silence()
   */
  static int fill_silence_frames(struct snd_pcm_substream *substream,
  			       snd_pcm_uframes_t off, snd_pcm_uframes_t frames)
  {
  	if (substream->runtime->access == SNDRV_PCM_ACCESS_RW_INTERLEAVED ||
  	    substream->runtime->access == SNDRV_PCM_ACCESS_MMAP_INTERLEAVED)
  		return interleaved_copy(substream, off, NULL, 0, frames,
  					fill_silence);
  	else
  		return noninterleaved_copy(substream, off, NULL, 0, frames,
  					   fill_silence);
  }
  
  /* sanity-check for read/write methods */
  static int pcm_sanity_check(struct snd_pcm_substream *substream)
  {
  	struct snd_pcm_runtime *runtime;
  	if (PCM_RUNTIME_CHECK(substream))
  		return -ENXIO;
  	runtime = substream->runtime;
  	if (snd_BUG_ON(!substream->ops->copy_user && !runtime->dma_area))
  		return -EINVAL;
  	if (runtime->status->state == SNDRV_PCM_STATE_OPEN)
  		return -EBADFD;
  	return 0;
  }
  
  static int pcm_accessible_state(struct snd_pcm_runtime *runtime)
  {
  	switch (runtime->status->state) {
  	case SNDRV_PCM_STATE_PREPARED:
  	case SNDRV_PCM_STATE_RUNNING:
  	case SNDRV_PCM_STATE_PAUSED:
  		return 0;
  	case SNDRV_PCM_STATE_XRUN:
  		return -EPIPE;
  	case SNDRV_PCM_STATE_SUSPENDED:
  		return -ESTRPIPE;
  	default:
  		return -EBADFD;
  	}
  }
  
  /* update to the given appl_ptr and call ack callback if needed;
   * when an error is returned, take back to the original value
   */
  int pcm_lib_apply_appl_ptr(struct snd_pcm_substream *substream,
  			   snd_pcm_uframes_t appl_ptr)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	snd_pcm_uframes_t old_appl_ptr = runtime->control->appl_ptr;
  	int ret;
  
  	if (old_appl_ptr == appl_ptr)
  		return 0;
  
  	runtime->control->appl_ptr = appl_ptr;
  	if (substream->ops->ack) {
  		ret = substream->ops->ack(substream);
  		if (ret < 0) {
  			runtime->control->appl_ptr = old_appl_ptr;
  			return ret;
  		}
  	}
  
  	trace_applptr(substream, old_appl_ptr, appl_ptr);
  
  	return 0;
  }
  
  /* the common loop for read/write data */
  snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream,
  				     void *data, bool interleaved,
  				     snd_pcm_uframes_t size, bool in_kernel)
  {
  	struct snd_pcm_runtime *runtime = substream->runtime;
  	snd_pcm_uframes_t xfer = 0;
  	snd_pcm_uframes_t offset = 0;
  	snd_pcm_uframes_t avail;
  	pcm_copy_f writer;
  	pcm_transfer_f transfer;
  	bool nonblock;
  	bool is_playback;
  	int err;
  
  	err = pcm_sanity_check(substream);
  	if (err < 0)
  		return err;
  
  	is_playback = substream->stream == SNDRV_PCM_STREAM_PLAYBACK;
  	if (interleaved) {
  		if (runtime->access != SNDRV_PCM_ACCESS_RW_INTERLEAVED &&
  		    runtime->channels > 1)
  			return -EINVAL;
  		writer = interleaved_copy;
  	} else {
  		if (runtime->access != SNDRV_PCM_ACCESS_RW_NONINTERLEAVED)
  			return -EINVAL;
  		writer = noninterleaved_copy;
  	}
  
  	if (!data) {
  		if (is_playback)
  			transfer = fill_silence;
  		else
  			return -EINVAL;
  	} else if (in_kernel) {
  		if (substream->ops->copy_kernel)
  			transfer = substream->ops->copy_kernel;
  		else
  			transfer = is_playback ?
  				default_write_copy_kernel : default_read_copy_kernel;
  	} else {
  		if (substream->ops->copy_user)
  			transfer = (pcm_transfer_f)substream->ops->copy_user;
  		else
  			transfer = is_playback ?
  				default_write_copy : default_read_copy;
  	}
  
  	if (size == 0)
  		return 0;
  
  	nonblock = !!(substream->f_flags & O_NONBLOCK);
  
  	snd_pcm_stream_lock_irq(substream);
  	err = pcm_accessible_state(runtime);
  	if (err < 0)
  		goto _end_unlock;
  
  	runtime->twake = runtime->control->avail_min ? : 1;
  	if (runtime->status->state == SNDRV_PCM_STATE_RUNNING)
  		snd_pcm_update_hw_ptr(substream);
  
  	/*
  	 * If size < start_threshold, wait indefinitely. Another
  	 * thread may start capture
  	 */
  	if (!is_playback &&
  	    runtime->status->state == SNDRV_PCM_STATE_PREPARED &&
  	    size >= runtime->start_threshold) {
  		err = snd_pcm_start(substream);
  		if (err < 0)
  			goto _end_unlock;
  	}
  
  	avail = snd_pcm_avail(substream);
  
  	while (size > 0) {
  		snd_pcm_uframes_t frames, appl_ptr, appl_ofs;
  		snd_pcm_uframes_t cont;
  		if (!avail) {
  			if (!is_playback &&
  			    runtime->status->state == SNDRV_PCM_STATE_DRAINING) {
  				snd_pcm_stop(substream, SNDRV_PCM_STATE_SETUP);
  				goto _end_unlock;
  			}
  			if (nonblock) {
  				err = -EAGAIN;
  				goto _end_unlock;
  			}
  			runtime->twake = min_t(snd_pcm_uframes_t, size,
  					runtime->control->avail_min ? : 1);
  			err = wait_for_avail(substream, &avail);
  			if (err < 0)
  				goto _end_unlock;
  			if (!avail)
  				continue; /* draining */
  		}
  		frames = size > avail ? avail : size;
  		appl_ptr = READ_ONCE(runtime->control->appl_ptr);
  		appl_ofs = appl_ptr % runtime->buffer_size;
  		cont = runtime->buffer_size - appl_ofs;
  		if (frames > cont)
  			frames = cont;
  		if (snd_BUG_ON(!frames)) {
  			err = -EINVAL;
  			goto _end_unlock;
  		}
  		snd_pcm_stream_unlock_irq(substream);
  		err = writer(substream, appl_ofs, data, offset, frames,
  			     transfer);
  		snd_pcm_stream_lock_irq(substream);
  		if (err < 0)
  			goto _end_unlock;
  		err = pcm_accessible_state(runtime);
  		if (err < 0)
  			goto _end_unlock;
  		appl_ptr += frames;
  		if (appl_ptr >= runtime->boundary)
  			appl_ptr -= runtime->boundary;
  		err = pcm_lib_apply_appl_ptr(substream, appl_ptr);
  		if (err < 0)
  			goto _end_unlock;
  
  		offset += frames;
  		size -= frames;
  		xfer += frames;
  		avail -= frames;
  		if (is_playback &&
  		    runtime->status->state == SNDRV_PCM_STATE_PREPARED &&
  		    snd_pcm_playback_hw_avail(runtime) >= (snd_pcm_sframes_t)runtime->start_threshold) {
  			err = snd_pcm_start(substream);
  			if (err < 0)
  				goto _end_unlock;
  		}
  	}
   _end_unlock:
  	runtime->twake = 0;
  	if (xfer > 0 && err >= 0)
  		snd_pcm_update_state(substream, runtime);
  	snd_pcm_stream_unlock_irq(substream);
  	return xfer > 0 ? (snd_pcm_sframes_t)xfer : err;
  }
  EXPORT_SYMBOL(__snd_pcm_lib_xfer);
  
  /*
   * standard channel mapping helpers
   */
  
  /* default channel maps for multi-channel playbacks, up to 8 channels */
  const struct snd_pcm_chmap_elem snd_pcm_std_chmaps[] = {
  	{ .channels = 1,
  	  .map = { SNDRV_CHMAP_MONO } },
  	{ .channels = 2,
  	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR } },
  	{ .channels = 4,
  	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR,
  		   SNDRV_CHMAP_RL, SNDRV_CHMAP_RR } },
  	{ .channels = 6,
  	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR,
  		   SNDRV_CHMAP_RL, SNDRV_CHMAP_RR,
  		   SNDRV_CHMAP_FC, SNDRV_CHMAP_LFE } },
  	{ .channels = 8,
  	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR,
  		   SNDRV_CHMAP_RL, SNDRV_CHMAP_RR,
  		   SNDRV_CHMAP_FC, SNDRV_CHMAP_LFE,
  		   SNDRV_CHMAP_SL, SNDRV_CHMAP_SR } },
  	{ }
  };
  EXPORT_SYMBOL_GPL(snd_pcm_std_chmaps);
  
  /* alternative channel maps with CLFE <-> surround swapped for 6/8 channels */
  const struct snd_pcm_chmap_elem snd_pcm_alt_chmaps[] = {
  	{ .channels = 1,
  	  .map = { SNDRV_CHMAP_MONO } },
  	{ .channels = 2,
  	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR } },
  	{ .channels = 4,
  	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR,
  		   SNDRV_CHMAP_RL, SNDRV_CHMAP_RR } },
  	{ .channels = 6,
  	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR,
  		   SNDRV_CHMAP_FC, SNDRV_CHMAP_LFE,
  		   SNDRV_CHMAP_RL, SNDRV_CHMAP_RR } },
  	{ .channels = 8,
  	  .map = { SNDRV_CHMAP_FL, SNDRV_CHMAP_FR,
  		   SNDRV_CHMAP_FC, SNDRV_CHMAP_LFE,
  		   SNDRV_CHMAP_RL, SNDRV_CHMAP_RR,
  		   SNDRV_CHMAP_SL, SNDRV_CHMAP_SR } },
  	{ }
  };
  EXPORT_SYMBOL_GPL(snd_pcm_alt_chmaps);
  
  static bool valid_chmap_channels(const struct snd_pcm_chmap *info, int ch)
  {
  	if (ch > info->max_channels)
  		return false;
  	return !info->channel_mask || (info->channel_mask & (1U << ch));
  }
  
  static int pcm_chmap_ctl_info(struct snd_kcontrol *kcontrol,
  			      struct snd_ctl_elem_info *uinfo)
  {
  	struct snd_pcm_chmap *info = snd_kcontrol_chip(kcontrol);
  
  	uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
  	uinfo->count = info->max_channels;
  	uinfo->value.integer.min = 0;
  	uinfo->value.integer.max = SNDRV_CHMAP_LAST;
  	return 0;
  }
  
  /* get callback for channel map ctl element
   * stores the channel position firstly matching with the current channels
   */
  static int pcm_chmap_ctl_get(struct snd_kcontrol *kcontrol,
  			     struct snd_ctl_elem_value *ucontrol)
  {
  	struct snd_pcm_chmap *info = snd_kcontrol_chip(kcontrol);
  	unsigned int idx = snd_ctl_get_ioffidx(kcontrol, &ucontrol->id);
  	struct snd_pcm_substream *substream;
  	const struct snd_pcm_chmap_elem *map;
  
  	if (!info->chmap)
  		return -EINVAL;
  	substream = snd_pcm_chmap_substream(info, idx);
  	if (!substream)
  		return -ENODEV;
  	memset(ucontrol->value.integer.value, 0,
  	       sizeof(long) * info->max_channels);
  	if (!substream->runtime)
  		return 0; /* no channels set */
  	for (map = info->chmap; map->channels; map++) {
  		int i;
  		if (map->channels == substream->runtime->channels &&
  		    valid_chmap_channels(info, map->channels)) {
  			for (i = 0; i < map->channels; i++)
  				ucontrol->value.integer.value[i] = map->map[i];
  			return 0;
  		}
  	}
  	return -EINVAL;
  }
  
  /* tlv callback for channel map ctl element
   * expands the pre-defined channel maps in a form of TLV
   */
  static int pcm_chmap_ctl_tlv(struct snd_kcontrol *kcontrol, int op_flag,
  			     unsigned int size, unsigned int __user *tlv)
  {
  	struct snd_pcm_chmap *info = snd_kcontrol_chip(kcontrol);
  	const struct snd_pcm_chmap_elem *map;
  	unsigned int __user *dst;
  	int c, count = 0;
  
  	if (!info->chmap)
  		return -EINVAL;
  	if (size < 8)
  		return -ENOMEM;
  	if (put_user(SNDRV_CTL_TLVT_CONTAINER, tlv))
  		return -EFAULT;
  	size -= 8;
  	dst = tlv + 2;
  	for (map = info->chmap; map->channels; map++) {
  		int chs_bytes = map->channels * 4;
  		if (!valid_chmap_channels(info, map->channels))
  			continue;
  		if (size < 8)
  			return -ENOMEM;
  		if (put_user(SNDRV_CTL_TLVT_CHMAP_FIXED, dst) ||
  		    put_user(chs_bytes, dst + 1))
  			return -EFAULT;
  		dst += 2;
  		size -= 8;
  		count += 8;
  		if (size < chs_bytes)
  			return -ENOMEM;
  		size -= chs_bytes;
  		count += chs_bytes;
  		for (c = 0; c < map->channels; c++) {
  			if (put_user(map->map[c], dst))
  				return -EFAULT;
  			dst++;
  		}
  	}
  	if (put_user(count, tlv + 1))
  		return -EFAULT;
  	return 0;
  }
  
  static void pcm_chmap_ctl_private_free(struct snd_kcontrol *kcontrol)
  {
  	struct snd_pcm_chmap *info = snd_kcontrol_chip(kcontrol);
  	info->pcm->streams[info->stream].chmap_kctl = NULL;
  	kfree(info);
  }
  
  /**
   * snd_pcm_add_chmap_ctls - create channel-mapping control elements
   * @pcm: the assigned PCM instance
   * @stream: stream direction
   * @chmap: channel map elements (for query)
   * @max_channels: the max number of channels for the stream
   * @private_value: the value passed to each kcontrol's private_value field
   * @info_ret: store struct snd_pcm_chmap instance if non-NULL
   *
   * Create channel-mapping control elements assigned to the given PCM stream(s).
   * Return: Zero if successful, or a negative error value.
   */
  int snd_pcm_add_chmap_ctls(struct snd_pcm *pcm, int stream,
  			   const struct snd_pcm_chmap_elem *chmap,
  			   int max_channels,
  			   unsigned long private_value,
  			   struct snd_pcm_chmap **info_ret)
  {
  	struct snd_pcm_chmap *info;
  	struct snd_kcontrol_new knew = {
  		.iface = SNDRV_CTL_ELEM_IFACE_PCM,
  		.access = SNDRV_CTL_ELEM_ACCESS_READ |
  			SNDRV_CTL_ELEM_ACCESS_TLV_READ |
  			SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK,
  		.info = pcm_chmap_ctl_info,
  		.get = pcm_chmap_ctl_get,
  		.tlv.c = pcm_chmap_ctl_tlv,
  	};
  	int err;
  
  	if (WARN_ON(pcm->streams[stream].chmap_kctl))
  		return -EBUSY;
  	info = kzalloc(sizeof(*info), GFP_KERNEL);
  	if (!info)
  		return -ENOMEM;
  	info->pcm = pcm;
  	info->stream = stream;
  	info->chmap = chmap;
  	info->max_channels = max_channels;
  	if (stream == SNDRV_PCM_STREAM_PLAYBACK)
  		knew.name = "Playback Channel Map";
  	else
  		knew.name = "Capture Channel Map";
  	knew.device = pcm->device;
  	knew.count = pcm->streams[stream].substream_count;
  	knew.private_value = private_value;
  	info->kctl = snd_ctl_new1(&knew, info);
  	if (!info->kctl) {
  		kfree(info);
  		return -ENOMEM;
  	}
  	info->kctl->private_free = pcm_chmap_ctl_private_free;
  	err = snd_ctl_add(pcm->card, info->kctl);
  	if (err < 0)
  		return err;
  	pcm->streams[stream].chmap_kctl = info->kctl;
  	if (info_ret)
  		*info_ret = info;
  	return 0;
  }
  EXPORT_SYMBOL_GPL(snd_pcm_add_chmap_ctls);
  