text: /*
   * amdtp-ff.c - a part of driver for RME Fireface series
   *
   * Copyright (c) 2015-2017 Takashi Sakamoto
   *
   * Licensed under the terms of the GNU General Public License, version 2.
   */
  
  #include <sound/pcm.h>
  #include "ff.h"
  
  struct amdtp_ff {
  	unsigned int pcm_channels;
  };
  
  int amdtp_ff_set_parameters(struct amdtp_stream *s, unsigned int rate,
  			    unsigned int pcm_channels)
  {
  	struct amdtp_ff *p = s->protocol;
  	unsigned int data_channels;
  
  	if (amdtp_stream_running(s))
  		return -EBUSY;
  
  	p->pcm_channels = pcm_channels;
  	data_channels = pcm_channels;
  
  	return amdtp_stream_set_parameters(s, rate, data_channels);
  }
  
  static void write_pcm_s32(struct amdtp_stream *s,
  			  struct snd_pcm_substream *pcm,
  			  __le32 *buffer, unsigned int frames)
  {
  	struct amdtp_ff *p = s->protocol;
  	struct snd_pcm_runtime *runtime = pcm->runtime;
  	unsigned int channels, remaining_frames, i, c;
  	const u32 *src;
  
  	channels = p->pcm_channels;
  	src = (void *)runtime->dma_area +
  			frames_to_bytes(runtime, s->pcm_buffer_pointer);
  	remaining_frames = runtime->buffer_size - s->pcm_buffer_pointer;
  
  	for (i = 0; i < frames; ++i) {
  		for (c = 0; c < channels; ++c) {
  			buffer[c] = cpu_to_le32(*src);
  			src++;
  		}
  		buffer += s->data_block_quadlets;
  		if (--remaining_frames == 0)
  			src = (void *)runtime->dma_area;
  	}
  }
  
  static void read_pcm_s32(struct amdtp_stream *s,
  			 struct snd_pcm_substream *pcm,
  			 __le32 *buffer, unsigned int frames)
  {
  	struct amdtp_ff *p = s->protocol;
  	struct snd_pcm_runtime *runtime = pcm->runtime;
  	unsigned int channels, remaining_frames, i, c;
  	u32 *dst;
  
  	channels = p->pcm_channels;
  	dst  = (void *)runtime->dma_area +
  			frames_to_bytes(runtime, s->pcm_buffer_pointer);
  	remaining_frames = runtime->buffer_size - s->pcm_buffer_pointer;
  
  	for (i = 0; i < frames; ++i) {
  		for (c = 0; c < channels; ++c) {
  			*dst = le32_to_cpu(buffer[c]) & 0xffffff00;
  			dst++;
  		}
  		buffer += s->data_block_quadlets;
  		if (--remaining_frames == 0)
  			dst = (void *)runtime->dma_area;
  	}
  }
  
  static void write_pcm_silence(struct amdtp_stream *s,
  			      __le32 *buffer, unsigned int frames)
  {
  	struct amdtp_ff *p = s->protocol;
  	unsigned int i, c, channels = p->pcm_channels;
  
  	for (i = 0; i < frames; ++i) {
  		for (c = 0; c < channels; ++c)
  			buffer[c] = cpu_to_le32(0x00000000);
  		buffer += s->data_block_quadlets;
  	}
  }
  
  int amdtp_ff_add_pcm_hw_constraints(struct amdtp_stream *s,
  				    struct snd_pcm_runtime *runtime)
  {
  	int err;
  
  	err = snd_pcm_hw_constraint_msbits(runtime, 0, 32, 24);
  	if (err < 0)
  		return err;
  
  	return amdtp_stream_add_pcm_hw_constraints(s, runtime);
  }
  
  static unsigned int process_rx_data_blocks(struct amdtp_stream *s,
  					   __be32 *buffer,
  					   unsigned int data_blocks,
  					   unsigned int *syt)
  {
  	struct snd_pcm_substream *pcm = ACCESS_ONCE(s->pcm);
  	unsigned int pcm_frames;
  
  	if (pcm) {
  		write_pcm_s32(s, pcm, (__le32 *)buffer, data_blocks);
  		pcm_frames = data_blocks;
  	} else {
  		write_pcm_silence(s, (__le32 *)buffer, data_blocks);
  		pcm_frames = 0;
  	}
  
  	return pcm_frames;
  }
  
  static unsigned int process_tx_data_blocks(struct amdtp_stream *s,
  					   __be32 *buffer,
  					   unsigned int data_blocks,
  					   unsigned int *syt)
  {
  	struct snd_pcm_substream *pcm = ACCESS_ONCE(s->pcm);
  	unsigned int pcm_frames;
  
  	if (pcm) {
  		read_pcm_s32(s, pcm, (__le32 *)buffer, data_blocks);
  		pcm_frames = data_blocks;
  	} else {
  		pcm_frames = 0;
  	}
  
  	return pcm_frames;
  }
  
  int amdtp_ff_init(struct amdtp_stream *s, struct fw_unit *unit,
  		  enum amdtp_stream_direction dir)
  {
  	amdtp_stream_process_data_blocks_t process_data_blocks;
  
  	if (dir == AMDTP_IN_STREAM)
  		process_data_blocks = process_tx_data_blocks;
  	else
  		process_data_blocks = process_rx_data_blocks;
  
  	return amdtp_stream_init(s, unit, dir, CIP_NO_HEADER, 0,
  				 process_data_blocks, sizeof(struct amdtp_ff));
  }
  