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pcm-indirect.h

/*
 * Helper functions for indirect PCM data transfer
 *
 *  Copyright (c) by Takashi Iwai <tiwai@suse.de>
 *                   Jaroslav Kysela <perex@suse.cz>
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#ifndef __SOUND_PCM_INDIRECT_H
#define __SOUND_PCM_INDIRECT_H

#include <sound/pcm.h>

struct snd_pcm_indirect {
      unsigned int hw_buffer_size;  /* Byte size of hardware buffer */
      unsigned int hw_queue_size;   /* Max queue size of hw buffer (0 = buffer size) */
      unsigned int hw_data;   /* Offset to next dst (or src) in hw ring buffer */
      unsigned int hw_io;     /* Ring buffer hw pointer */
      int hw_ready;           /* Bytes ready for play (or captured) in hw ring buffer */
      unsigned int sw_buffer_size;  /* Byte size of software buffer */
      unsigned int sw_data;   /* Offset to next dst (or src) in sw ring buffer */
      unsigned int sw_io;     /* Current software pointer in bytes */
      int sw_ready;           /* Bytes ready to be transferred to/from hw */
      snd_pcm_uframes_t appl_ptr;   /* Last seen appl_ptr */
};

typedef void (*snd_pcm_indirect_copy_t)(struct snd_pcm_substream *substream,
                              struct snd_pcm_indirect *rec, size_t bytes);

/*
 * helper function for playback ack callback
 */
static inline void
snd_pcm_indirect_playback_transfer(struct snd_pcm_substream *substream,
                           struct snd_pcm_indirect *rec,
                           snd_pcm_indirect_copy_t copy)
{
      struct snd_pcm_runtime *runtime = substream->runtime;
      snd_pcm_uframes_t appl_ptr = runtime->control->appl_ptr;
      snd_pcm_sframes_t diff = appl_ptr - rec->appl_ptr;
      int qsize;

      if (diff) {
            if (diff < -(snd_pcm_sframes_t) (runtime->boundary / 2))
                  diff += runtime->boundary;
            rec->sw_ready += (int)frames_to_bytes(runtime, diff);
            rec->appl_ptr = appl_ptr;
      }
      qsize = rec->hw_queue_size ? rec->hw_queue_size : rec->hw_buffer_size;
      while (rec->hw_ready < qsize && rec->sw_ready > 0) {
            unsigned int hw_to_end = rec->hw_buffer_size - rec->hw_data;
            unsigned int sw_to_end = rec->sw_buffer_size - rec->sw_data;
            unsigned int bytes = qsize - rec->hw_ready;
            if (rec->sw_ready < (int)bytes)
                  bytes = rec->sw_ready;
            if (hw_to_end < bytes)
                  bytes = hw_to_end;
            if (sw_to_end < bytes)
                  bytes = sw_to_end;
            if (! bytes)
                  break;
            copy(substream, rec, bytes);
            rec->hw_data += bytes;
            if (rec->hw_data == rec->hw_buffer_size)
                  rec->hw_data = 0;
            rec->sw_data += bytes;
            if (rec->sw_data == rec->sw_buffer_size)
                  rec->sw_data = 0;
            rec->hw_ready += bytes;
            rec->sw_ready -= bytes;
      }
}

/*
 * helper function for playback pointer callback
 * ptr = current byte pointer
 */
static inline snd_pcm_uframes_t
snd_pcm_indirect_playback_pointer(struct snd_pcm_substream *substream,
                          struct snd_pcm_indirect *rec, unsigned int ptr)
{
      int bytes = ptr - rec->hw_io;
      if (bytes < 0)
            bytes += rec->hw_buffer_size;
      rec->hw_io = ptr;
      rec->hw_ready -= bytes;
      rec->sw_io += bytes;
      if (rec->sw_io >= rec->sw_buffer_size)
            rec->sw_io -= rec->sw_buffer_size;
      if (substream->ops->ack)
            substream->ops->ack(substream);
      return bytes_to_frames(substream->runtime, rec->sw_io);
}


/*
 * helper function for capture ack callback
 */
static inline void
snd_pcm_indirect_capture_transfer(struct snd_pcm_substream *substream,
                          struct snd_pcm_indirect *rec,
                          snd_pcm_indirect_copy_t copy)
{
      struct snd_pcm_runtime *runtime = substream->runtime;
      snd_pcm_uframes_t appl_ptr = runtime->control->appl_ptr;
      snd_pcm_sframes_t diff = appl_ptr - rec->appl_ptr;

      if (diff) {
            if (diff < -(snd_pcm_sframes_t) (runtime->boundary / 2))
                  diff += runtime->boundary;
            rec->sw_ready -= frames_to_bytes(runtime, diff);
            rec->appl_ptr = appl_ptr;
      }
      while (rec->hw_ready > 0 && 
             rec->sw_ready < (int)rec->sw_buffer_size) {
            size_t hw_to_end = rec->hw_buffer_size - rec->hw_data;
            size_t sw_to_end = rec->sw_buffer_size - rec->sw_data;
            size_t bytes = rec->sw_buffer_size - rec->sw_ready;
            if (rec->hw_ready < (int)bytes)
                  bytes = rec->hw_ready;
            if (hw_to_end < bytes)
                  bytes = hw_to_end;
            if (sw_to_end < bytes)
                  bytes = sw_to_end;
            if (! bytes)
                  break;
            copy(substream, rec, bytes);
            rec->hw_data += bytes;
            if ((int)rec->hw_data == rec->hw_buffer_size)
                  rec->hw_data = 0;
            rec->sw_data += bytes;
            if (rec->sw_data == rec->sw_buffer_size)
                  rec->sw_data = 0;
            rec->hw_ready -= bytes;
            rec->sw_ready += bytes;
      }
}

/*
 * helper function for capture pointer callback,
 * ptr = current byte pointer
 */
static inline snd_pcm_uframes_t
snd_pcm_indirect_capture_pointer(struct snd_pcm_substream *substream,
                         struct snd_pcm_indirect *rec, unsigned int ptr)
{
      int qsize;
      int bytes = ptr - rec->hw_io;
      if (bytes < 0)
            bytes += rec->hw_buffer_size;
      rec->hw_io = ptr;
      rec->hw_ready += bytes;
      qsize = rec->hw_queue_size ? rec->hw_queue_size : rec->hw_buffer_size;
      if (rec->hw_ready > qsize)
            return SNDRV_PCM_POS_XRUN;
      rec->sw_io += bytes;
      if (rec->sw_io >= rec->sw_buffer_size)
            rec->sw_io -= rec->sw_buffer_size;
      if (substream->ops->ack)
            substream->ops->ack(substream);
      return bytes_to_frames(substream->runtime, rec->sw_io);
}

#endif /* __SOUND_PCM_INDIRECT_H */

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