Fix boundary overlap

Fixed the possible bug with boundary overlap in dmix code.

diff --git a/src/pcm/pcm_dmix.c b/src/pcm/pcm_dmix.c
index 462a5a21c150588ec905d850c4779fff91beeeef..af4a67a9bcd79cfcd86cac7db7ef01ec54b3b4f4 100644 (file)
--- a/src/pcm/pcm_dmix.c
+++ b/src/pcm/pcm_dmix.c
@@ -239,13 +239,20 @@ static void snd_pcm_dmix_sync_area(snd_pcm_t *pcm)
 {
        snd_pcm_direct_t *dmix = pcm->private_data;
        snd_pcm_uframes_t appl_ptr, slave_appl_ptr, slave_bsize;
-       snd_pcm_uframes_t size, slave_hw_ptr;
+       snd_pcm_uframes_t size, slave_size, slave_hw_ptr;
        const snd_pcm_channel_area_t *src_areas, *dst_areas;
        
        /* calculate the size to transfer */
+       /* check the available size in the local buffer
+        * last_appl_ptr keeps the last updated position
+        */
        size = dmix->appl_ptr - dmix->last_appl_ptr;
        if (! size)
                return;
+       if (size >= pcm->boundary / 2)
+               size = pcm->boundary - size;
+
+       /* check the available size in the slave PCM buffer */
        slave_bsize = dmix->shmptr->s.buffer_size;
        slave_hw_ptr = dmix->slave_hw_ptr;
        /* don't write on the last active period - this area may be cleared
@@ -253,12 +260,17 @@ static void snd_pcm_dmix_sync_area(snd_pcm_t *pcm)
         */
        slave_hw_ptr -= slave_hw_ptr % dmix->shmptr->s.period_size;
        slave_hw_ptr += slave_bsize;
-       if (dmix->slave_hw_ptr > dmix->slave_appl_ptr)
+       if (slave_hw_ptr >= dmix->shmptr->s.boundary)
                slave_hw_ptr -= dmix->shmptr->s.boundary;
-       if (dmix->slave_appl_ptr + size >= slave_hw_ptr)
-               size = slave_hw_ptr - dmix->slave_appl_ptr;
+       if (slave_hw_ptr < dmix->slave_appl_ptr)
+               slave_size = slave_hw_ptr + (dmix->shmptr->s.boundary - dmix->slave_appl_ptr);
+       else
+               slave_size = slave_hw_ptr - dmix->slave_appl_ptr;
+       if (slave_size < size)
+               size = slave_size;
        if (! size)
                return;
+
        /* add sample areas here */
        src_areas = snd_pcm_mmap_areas(pcm);
        dst_areas = snd_pcm_mmap_areas(dmix->spcm);