ALSA: PCM midlevel: improve fifo_size handling

Move the fifo_size assignment to hw->ioctl callback to allow lowlevel
drivers overwrite the default behaviour.

fifo_size is in frames not bytes as specified in asound.h and alsa-lib's
documentation, but most hardware have fixed byte based FIFOs. Introduce
internal SNDRV_PCM_INFO_FIFO_IN_FRAMES.

Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

2 files changed, 2 insertions, 0 deletions

diff --git a/include/sound/asound.h b/include/sound/asound.h
index 6add80fc251..82aed3f4753 100644
--- a/include/sound/asound.h
+++ b/include/sound/asound.h
@@ -255,6 +255,7 @@ typedef int __bitwise snd_pcm_subformat_t;
 #define SNDRV_PCM_INFO_HALF_DUPLEX      0x00100000      /* only half duplex */
 #define SNDRV_PCM_INFO_JOINT_DUPLEX     0x00200000      /* playback and capture stream are somewhat correlated */
 #define SNDRV_PCM_INFO_SYNC_START       0x00400000      /* pcm support some kind of sync go */
+#define SNDRV_PCM_INFO_FIFO_IN_FRAMES   0x80000000      /* internal kernel flag - FIFO size is in frames */
 
 typedef int __bitwise snd_pcm_state_t;
 #define SNDRV_PCM_STATE_OPEN            ((__force snd_pcm_state_t) 0) /* stream is open */
diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index 267effddb07..8a69b5c1e1c 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -98,6 +98,7 @@ struct snd_pcm_ops {
 #define SNDRV_PCM_IOCTL1_INFO           1
 #define SNDRV_PCM_IOCTL1_CHANNEL_INFO   2
 #define SNDRV_PCM_IOCTL1_GSTATE         3
+#define SNDRV_PCM_IOCTL1_FIFO_SIZE      4
 
 #define SNDRV_PCM_TRIGGER_STOP          0
 #define SNDRV_PCM_TRIGGER_START         1