ALSA: pcm: Introduce protocol version field to sw_params

For controlling the new fields more strictly, add sw_params.proto
field indicating the protocol version of the user-space.  User-space
should fill the SNDRV_PCM_VERSION value it's built with, then kernel
can know whether the new fields should be evaluated or not.

And now tstamp_type field is evaluated only when the valid value is
set there.  This avoids the wrong override of tstamp_type to zero,
which is SNDRV_PCM_TSTAMP_TYPE_GETTIMEOFDAY.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

include/uapi/sound/asound.h

@@ -391,8 +391,8 @@ struct snd_pcm_sw_params {
 	snd_pcm_uframes_t silence_threshold;	/* min distance from noise for silence filling */
 	snd_pcm_uframes_t silence_size;		/* silence block size */
 	snd_pcm_uframes_t boundary;		/* pointers wrap point */
-	unsigned int tstamp_type;		/* timestamp type */
-	int pads;				/* alignment, reserved */
+	unsigned int proto;			/* protocol version */
+	unsigned int tstamp_type;		/* timestamp type (req. proto >= 2.0.12) */
 	unsigned char reserved[56];		/* reserved for future */
 };
 

sound/core/pcm_native.c

@@ -543,7 +543,8 @@ static int snd_pcm_sw_params(struct snd_pcm_substream *substream,
 
 	if (params->tstamp_mode > SNDRV_PCM_TSTAMP_LAST)
 		return -EINVAL;
-	if (params->tstamp_type > SNDRV_PCM_TSTAMP_TYPE_LAST)
+	if (params->proto >= SNDRV_PROTOCOL_VERSION(2, 0, 12) &&
+	    params->tstamp_type > SNDRV_PCM_TSTAMP_TYPE_LAST)
 		return -EINVAL;
 	if (params->avail_min == 0)
 		return -EINVAL;
@@ -559,6 +560,7 @@ static int snd_pcm_sw_params(struct snd_pcm_substream *substream,
 	err = 0;
 	snd_pcm_stream_lock_irq(substream);
 	runtime->tstamp_mode = params->tstamp_mode;
+	if (params->proto >= SNDRV_PROTOCOL_VERSION(2, 0, 12))
 		runtime->tstamp_type = params->tstamp_type;
 	runtime->period_step = params->period_step;
 	runtime->control->avail_min = params->avail_min;