text: /* SPDX-License-Identifier: GPL-2.0-or-later */
  /*
   * Helper functions for indirect PCM data transfer to a simple FIFO in
   * hardware (small, no possibility to read "hardware io position",
   * updating position done by interrupt, ...)
   *
   *  Copyright (c) by 2007  Joachim Foerster <JOFT@gmx.de>
   *
   *  Based on "pcm-indirect.h" (alsa-driver-1.0.13) by
   *
   *  Copyright (c) by Takashi Iwai <tiwai@suse.de>
   *                   Jaroslav Kysela <perex@suse.cz>
   */
  
  #ifndef __SOUND_PCM_INDIRECT2_H
  #define __SOUND_PCM_INDIRECT2_H
  
  /* struct snd_pcm_substream, struct snd_pcm_runtime, snd_pcm_uframes_t */
  #include <sound/pcm.h>
  
  /* Debug options for code which may be removed completely in a final version */
  #ifdef CONFIG_SND_DEBUG
  #define SND_PCM_INDIRECT2_STAT    /* turn on some "statistics" about the
  				   * process of copying bytes from the
  				   * intermediate buffer to the hardware
  				   * fifo and the other way round
  				   */
  #endif
  
  struct snd_pcm_indirect2 {
  	unsigned int hw_buffer_size;  /* Byte size of hardware buffer */
  	int hw_ready;		      /* playback: 1 = hw fifo has room left,
  				       * 0 = hw fifo is full
  				       */
  	unsigned int min_multiple;
  	int min_periods;	      /* counts number of min. periods until
  				       * min_multiple is reached
  				       */
  	int min_period_count;	      /* counts bytes to count number of
  				       * min. periods
  				       */
  
  	unsigned int sw_buffer_size;  /* Byte size of software buffer */
  
  	/* sw_data: position in intermediate buffer, where we will read (or
  	 *          write) from/to next time (to transfer data to/from HW)
  	 */
  	unsigned int sw_data;         /* Offset to next dst (or src) in sw
  				       * ring buffer
  				       */
  	/* easiest case (playback):
  	 * sw_data is nearly the same as ~ runtime->control->appl_ptr, with the
  	 * exception that sw_data is "behind" by the number if bytes ALSA wrote
  	 * to the intermediate buffer last time.
  	 * A call to ack() callback synchronizes both indirectly.
  	 */
  
  	/* We have no real sw_io pointer here. Usually sw_io is pointing to the
  	 * current playback/capture position _inside_ the hardware. Devices
  	 * with plain FIFOs often have no possibility to publish this position.
  	 * So we say: if sw_data is updated, that means bytes were copied to
  	 * the hardware, we increase sw_io by that amount, because there have
  	 * to be as much bytes which were played. So sw_io will stay behind
  	 * sw_data all the time and has to converge to sw_data at the end of
  	 * playback.
  	 */
  	unsigned int sw_io;           /* Current software pointer in bytes */
  
  	/* sw_ready: number of bytes ALSA copied to the intermediate buffer, so
  	 * it represents the number of bytes which wait for transfer to the HW
  	 */
  	int sw_ready;		  /* Bytes ready to be transferred to/from hw */
  
  	/* appl_ptr: last known position of ALSA (where ALSA is going to write
  	 * next time into the intermediate buffer
  	 */
  	snd_pcm_uframes_t appl_ptr;   /* Last seen appl_ptr */
  
  	unsigned int bytes2hw;
  	int check_alignment;
  
  #ifdef SND_PCM_INDIRECT2_STAT
  	unsigned int zeros2hw;
  	unsigned int mul_elapsed;
  	unsigned int mul_elapsed_real;
  	unsigned long firstbytetime;
  	unsigned long lastbytetime;
  	unsigned long firstzerotime;
  	unsigned int byte_sizes[64];
  	unsigned int zero_sizes[64];
  	unsigned int min_adds[8];
  	unsigned int mul_adds[8];
  	unsigned int zero_times[3750];	/* = 15s */
  	unsigned int zero_times_saved;
  	unsigned int zero_times_notsaved;
  	unsigned int irq_occured;
  	unsigned int pointer_calls;
  	unsigned int lastdifftime;
  #endif
  };
  
  typedef size_t (*snd_pcm_indirect2_copy_t) (struct snd_pcm_substream *substream,
  					   struct snd_pcm_indirect2 *rec,
  					   size_t bytes);
  typedef size_t (*snd_pcm_indirect2_zero_t) (struct snd_pcm_substream *substream,
  					   struct snd_pcm_indirect2 *rec);
  
  #ifdef SND_PCM_INDIRECT2_STAT
  void snd_pcm_indirect2_stat(struct snd_pcm_substream *substream,
  				   struct snd_pcm_indirect2 *rec);
  #endif
  
  snd_pcm_uframes_t
  snd_pcm_indirect2_pointer(struct snd_pcm_substream *substream,
  			  struct snd_pcm_indirect2 *rec);
  void
  snd_pcm_indirect2_playback_interrupt(struct snd_pcm_substream *substream,
  				     struct snd_pcm_indirect2 *rec,
  				     snd_pcm_indirect2_copy_t copy,
  				     snd_pcm_indirect2_zero_t zero);
  void
  snd_pcm_indirect2_capture_interrupt(struct snd_pcm_substream *substream,
  				    struct snd_pcm_indirect2 *rec,
  				    snd_pcm_indirect2_copy_t copy,
  				    snd_pcm_indirect2_zero_t null);
  
  #endif /* __SOUND_PCM_INDIRECT2_H */
  