[ALSA] Remove PCM xfer_align sw params

The xfer_align sw_params parameter has never been used in a sane manner,
and no one understands what this does exactly.  The current
implementation looks also buggy because it allows write of shorter size
than xfer_align.  So, if you do partial writes, the write isn't actually
aligned at all.
Removing this parameter will make some pcm_lib_* code more readable
(and less buggy).

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

Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl

@@ -2188,7 +2188,6 @@ struct _snd_pcm_runtime {
 	struct timespec tstamp_mode;	/* mmap timestamp is updated */
   	unsigned int period_step;
 	unsigned int sleep_min;		/* min ticks to sleep */
-	snd_pcm_uframes_t xfer_align;	/* xfer size need to be a multiple */
 	snd_pcm_uframes_t start_threshold;
 	snd_pcm_uframes_t stop_threshold;
 	snd_pcm_uframes_t silence_threshold; /* Silence filling happens when

include/sound/asound.h

@@ -363,7 +363,7 @@ struct snd_pcm_sw_params {
 	unsigned int period_step;
 	unsigned int sleep_min;			/* min ticks to sleep */
 	snd_pcm_uframes_t avail_min;		/* min avail frames for wakeup */
-	snd_pcm_uframes_t xfer_align;		/* xfer size need to be a multiple */
+	snd_pcm_uframes_t xfer_align;		/* obsolete: xfer size need to be a multiple */
 	snd_pcm_uframes_t start_threshold;	/* min hw_avail frames for automatic start */
 	snd_pcm_uframes_t stop_threshold;	/* min avail frames for automatic stop */
 	snd_pcm_uframes_t silence_threshold;	/* min distance from noise for silence filling */

include/sound/pcm.h

@@ -287,7 +287,6 @@ struct snd_pcm_runtime {
 	int tstamp_mode;		/* mmap timestamp is updated */
   	unsigned int period_step;
 	unsigned int sleep_min;		/* min ticks to sleep */
-	snd_pcm_uframes_t xfer_align;	/* xfer size need to be a multiple */
 	snd_pcm_uframes_t start_threshold;
 	snd_pcm_uframes_t stop_threshold;
 	snd_pcm_uframes_t silence_threshold; /* Silence filling happens when

sound/core/oss/pcm_oss.c

@@ -988,7 +988,6 @@ static int snd_pcm_oss_change_params(struct snd_pcm_substream *substream)
 	sw_params->sleep_min = 0;
 	sw_params->avail_min = substream->stream == SNDRV_PCM_STREAM_PLAYBACK ?
 		1 : runtime->period_size;
-	sw_params->xfer_align = 1;
 	if (atomic_read(&substream->mmap_count) ||
 	    substream->oss.setup.nosilence) {
 		sw_params->silence_threshold = 0;

sound/core/pcm.c

@@ -389,7 +389,6 @@ static void snd_pcm_substream_proc_sw_params_read(struct snd_info_entry *entry,
 	snd_iprintf(buffer, "period_step: %u\n", runtime->period_step);
 	snd_iprintf(buffer, "sleep_min: %u\n", runtime->sleep_min);
 	snd_iprintf(buffer, "avail_min: %lu\n", runtime->control->avail_min);
-	snd_iprintf(buffer, "xfer_align: %lu\n", runtime->xfer_align);
 	snd_iprintf(buffer, "start_threshold: %lu\n", runtime->start_threshold);
 	snd_iprintf(buffer, "stop_threshold: %lu\n", runtime->stop_threshold);
 	snd_iprintf(buffer, "silence_threshold: %lu\n", runtime->silence_threshold);

sound/core/pcm_lib.c

@@ -1628,8 +1628,6 @@ static snd_pcm_sframes_t snd_pcm_lib_write1(struct snd_pcm_substream *substream,
 
 	if (size == 0)
 		return 0;
-	if (size > runtime->xfer_align)
-		size -= size % runtime->xfer_align;
 
 	snd_pcm_stream_lock_irq(substream);
 	switch (runtime->status->state) {
@@ -1657,9 +1655,7 @@ static snd_pcm_sframes_t snd_pcm_lib_write1(struct snd_pcm_substream *substream,
 		avail = snd_pcm_playback_avail(runtime);
 		if (!avail ||
 		    (snd_pcm_running(substream) &&
-		     ((avail < runtime->control->avail_min && size > avail) ||
-		      (size >= runtime->xfer_align &&
-		       avail < runtime->xfer_align)))) {
+		     (avail < runtime->control->avail_min && size > avail))) {
 			wait_queue_t wait;
 			enum { READY, SIGNALED, ERROR, SUSPENDED, EXPIRED, DROPPED } state;
 			long tout;
@@ -1731,8 +1727,6 @@ static snd_pcm_sframes_t snd_pcm_lib_write1(struct snd_pcm_substream *substream,
 				break;
 			}
 		}
-		if (avail > runtime->xfer_align)
-			avail -= avail % runtime->xfer_align;
 		frames = size > avail ? avail : size;
 		cont = runtime->buffer_size - runtime->control->appl_ptr % runtime->buffer_size;
 		if (frames > cont)
@@ -1900,8 +1894,6 @@ static snd_pcm_sframes_t snd_pcm_lib_read1(struct snd_pcm_substream *substream,
 
 	if (size == 0)
 		return 0;
-	if (size > runtime->xfer_align)
-		size -= size % runtime->xfer_align;
 
 	snd_pcm_stream_lock_irq(substream);
 	switch (runtime->status->state) {
@@ -1936,12 +1928,12 @@ static snd_pcm_sframes_t snd_pcm_lib_read1(struct snd_pcm_substream *substream,
 	      __draining:
 		avail = snd_pcm_capture_avail(runtime);
 		if (runtime->status->state == SNDRV_PCM_STATE_DRAINING) {
-			if (avail < runtime->xfer_align) {
+			if (!avail) {
 				err = -EPIPE;
 				goto _end_unlock;
 			}
-		} else if ((avail < runtime->control->avail_min && size > avail) ||
-			   (size >= runtime->xfer_align && avail < runtime->xfer_align)) {
+		} else if (avail < runtime->control->avail_min &&
+			   size > avail) {
 			wait_queue_t wait;
 			enum { READY, SIGNALED, ERROR, SUSPENDED, EXPIRED, DROPPED } state;
 			long tout;
@@ -2014,8 +2006,6 @@ static snd_pcm_sframes_t snd_pcm_lib_read1(struct snd_pcm_substream *substream,
 				break;
 			}
 		}
-		if (avail > runtime->xfer_align)
-			avail -= avail % runtime->xfer_align;
 		frames = size > avail ? avail : size;
 		cont = runtime->buffer_size - runtime->control->appl_ptr % runtime->buffer_size;
 		if (frames > cont)

sound/core/pcm_native.c

@@ -435,7 +435,6 @@ static int snd_pcm_hw_params(struct snd_pcm_substream *substream,
 	runtime->period_step = 1;
 	runtime->sleep_min = 0;
 	runtime->control->avail_min = runtime->period_size;
-	runtime->xfer_align = runtime->period_size;
 	runtime->start_threshold = 1;
 	runtime->stop_threshold = runtime->buffer_size;
 	runtime->silence_threshold = 0;
@@ -532,9 +531,6 @@ static int snd_pcm_sw_params(struct snd_pcm_substream *substream,
 		return -EINVAL;
 	if (params->avail_min == 0)
 		return -EINVAL;
-	if (params->xfer_align == 0 ||
-	    params->xfer_align % runtime->min_align != 0)
-		return -EINVAL;
 	if (params->silence_size >= runtime->boundary) {
 		if (params->silence_threshold != 0)
 			return -EINVAL;
@@ -553,7 +549,6 @@ static int snd_pcm_sw_params(struct snd_pcm_substream *substream,
 	runtime->stop_threshold = params->stop_threshold;
 	runtime->silence_threshold = params->silence_threshold;
 	runtime->silence_size = params->silence_size;
-	runtime->xfer_align = params->xfer_align;
         params->boundary = runtime->boundary;
 	if (snd_pcm_running(substream)) {
 		if (runtime->sleep_min)
@@ -2239,8 +2234,6 @@ static snd_pcm_sframes_t snd_pcm_playback_rewind(struct snd_pcm_substream *subst
 	}
 	if (frames > (snd_pcm_uframes_t)hw_avail)
 		frames = hw_avail;
-	else
-		frames -= frames % runtime->xfer_align;
 	appl_ptr = runtime->control->appl_ptr - frames;
 	if (appl_ptr < 0)
 		appl_ptr += runtime->boundary;
@@ -2289,8 +2282,6 @@ static snd_pcm_sframes_t snd_pcm_capture_rewind(struct snd_pcm_substream *substr
 	}
 	if (frames > (snd_pcm_uframes_t)hw_avail)
 		frames = hw_avail;
-	else
-		frames -= frames % runtime->xfer_align;
 	appl_ptr = runtime->control->appl_ptr - frames;
 	if (appl_ptr < 0)
 		appl_ptr += runtime->boundary;
@@ -2340,8 +2331,6 @@ static snd_pcm_sframes_t snd_pcm_playback_forward(struct snd_pcm_substream *subs
 	}
 	if (frames > (snd_pcm_uframes_t)avail)
 		frames = avail;
-	else
-		frames -= frames % runtime->xfer_align;
 	appl_ptr = runtime->control->appl_ptr + frames;
 	if (appl_ptr >= (snd_pcm_sframes_t)runtime->boundary)
 		appl_ptr -= runtime->boundary;
@@ -2391,8 +2380,6 @@ static snd_pcm_sframes_t snd_pcm_capture_forward(struct snd_pcm_substream *subst
 	}
 	if (frames > (snd_pcm_uframes_t)avail)
 		frames = avail;
-	else
-		frames -= frames % runtime->xfer_align;
 	appl_ptr = runtime->control->appl_ptr + frames;
 	if (appl_ptr >= (snd_pcm_sframes_t)runtime->boundary)
 		appl_ptr -= runtime->boundary;