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>

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 */

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

sound/core/pcm_lib.c

@@ -1524,6 +1524,23 @@ static int snd_pcm_lib_ioctl_channel_info(struct snd_pcm_substream *substream,
 	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, width;
+
+	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);
+		width = snd_pcm_format_physical_width(format);
+		params->fifo_size /= width * channels;
+	}
+	return 0;
+}
+
 /**
  * snd_pcm_lib_ioctl - a generic PCM ioctl callback
  * @substream: the pcm substream instance
@@ -1545,6 +1562,8 @@ int snd_pcm_lib_ioctl(struct snd_pcm_substream *substream,
 		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;
 }

sound/core/pcm_native.c

@@ -312,9 +312,18 @@ int snd_pcm_hw_refine(struct snd_pcm_substream *substream,
 
 	hw = &substream->runtime->hw;
 	if (!params->info)
-		params->info = hw->info;
-	if (!params->fifo_size)
-		params->fifo_size = hw->fifo_size;
+		params->info = hw->info & ~SNDRV_PCM_INFO_FIFO_IN_FRAMES;
+	if (!params->fifo_size) {
+		if (snd_mask_min(&params->masks[SNDRV_PCM_HW_PARAM_FORMAT]) ==
+		    snd_mask_max(&params->masks[SNDRV_PCM_HW_PARAM_FORMAT]) &&
+                    snd_mask_min(&params->masks[SNDRV_PCM_HW_PARAM_CHANNELS]) ==
+                    snd_mask_max(&params->masks[SNDRV_PCM_HW_PARAM_CHANNELS])) {
+			changed = substream->ops->ioctl(substream,
+					SNDRV_PCM_IOCTL1_FIFO_SIZE, params);
+			if (params < 0)
+				return changed;
+		}
+	}
 	params->rmask = 0;
 	return 0;
 }