pcm: rate: fix drain of partial period at end of buffer

In the case that:
* the buffer size is not an integer multiple of the period size, and
* drain must flush a partial period located before the end of the buffer
  but without a full period available, where
* these conditions may pertain to the source or slave pcm buffer, and
* because rate conversion is always done on a full period,
it is necessary to check that both a full source period is available
before source pcm buffer wrap and a full slave period is available
before slave pcm buffer wrap in order to use the simple, single-commit
implementation in snd_pcm_rate_commit_area().

The alternative fix would be to change snd_pcm_rate_write_areas1() to
take size and slave_size parameters. This would be more disruptive to
the code base, tricky to get right, and is unnecessary given that
snd_pcm_mmap_commit() only commits the partial period of actually valid
converted samples.

Fixes: 3047f8fa5a3d ("Fix possible problems of playback drain with rate plugin")
Signed-off-by: Alan Young <consult.awy@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/src/pcm/pcm_rate.c b/src/pcm/pcm_rate.c
index c45895a9df2759c00c659dd70b5ed224f33486be..ba5364c0c03aaaa26f9d110463a88314a1a99515 100644 (file)
--- a/src/pcm/pcm_rate.c
+++ b/src/pcm/pcm_rate.c
@@ -781,16 +781,25 @@ static int snd_pcm_rate_commit_area(snd_pcm_t *pcm, snd_pcm_rate_t *rate,
        snd_pcm_sframes_t result;
 
        areas = snd_pcm_mmap_areas(pcm);
-       if (cont >= size) {
+       /*
+        * Because snd_pcm_rate_write_areas1() below will convert a full source period
+        * then there had better be a full period available in the current buffer.
+        */
+       if (cont >= pcm->period_size) {
                result = snd_pcm_mmap_begin(rate->gen.slave, &slave_areas, &slave_offset, &slave_frames);
                if (result < 0)
                        return result;
-               if (slave_frames < slave_size) {
+               /*
+                * Because snd_pcm_rate_write_areas1() below will convert to a full slave period
+                * then there had better be a full slave period available in the slave buffer.
+                */
+               if (slave_frames < rate->gen.slave->period_size) {
                        snd_pcm_rate_write_areas1(pcm, areas, appl_offset, rate->sareas, 0);
                        goto __partial;
                }
                snd_pcm_rate_write_areas1(pcm, areas, appl_offset,
                                          slave_areas, slave_offset);
+               /* Only commit the requested slave_size, even if more was actually converted */
                result = snd_pcm_mmap_commit(rate->gen.slave, slave_offset, slave_size);
                if (result < (snd_pcm_sframes_t)slave_size) {
                        if (result < 0)