ALSA: pcm: Fix negative appl_ptr handling in pcm-indirect helpers

The indirect-PCM helper codes have an implicit assumption that the
appl_ptr always increases.  But the PCM core may deal with the
decrement of appl_ptr via rewind ioctls, and it may screw up the
buffer pointer management.

This patch adds the negative appl_ptr diff in transfer functions and
let returning an error instead of always accepting the appl_ptr
updates.  The callers are usually PCM ack callbacks, and they pass the
error to the upper layer accordingly.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/include/sound/pcm-indirect.h b/include/sound/pcm-indirect.h
index 1df7acaaa53527b10a79f390ab07573f17474881..7ade285328cf8a86f1c3f600128760c8428a3f6b 100644 (file)
--- a/include/sound/pcm-indirect.h
+++ b/include/sound/pcm-indirect.h
@@ -43,7 +43,7 @@ typedef void (*snd_pcm_indirect_copy_t)(struct snd_pcm_substream *substream,
 /*
  * helper function for playback ack callback
  */
-static inline void
+static inline int
 snd_pcm_indirect_playback_transfer(struct snd_pcm_substream *substream,
                                   struct snd_pcm_indirect *rec,
                                   snd_pcm_indirect_copy_t copy)
@@ -56,6 +56,8 @@ snd_pcm_indirect_playback_transfer(struct snd_pcm_substream *substream,
        if (diff) {
                if (diff < -(snd_pcm_sframes_t) (runtime->boundary / 2))
                        diff += runtime->boundary;
+               if (diff < 0)
+                       return -EINVAL;
                rec->sw_ready += (int)frames_to_bytes(runtime, diff);
                rec->appl_ptr = appl_ptr;
        }
@@ -82,6 +84,7 @@ snd_pcm_indirect_playback_transfer(struct snd_pcm_substream *substream,
                rec->hw_ready += bytes;
                rec->sw_ready -= bytes;
        }
+       return 0;
 }
 
 /*
@@ -109,7 +112,7 @@ snd_pcm_indirect_playback_pointer(struct snd_pcm_substream *substream,
 /*
  * helper function for capture ack callback
  */
-static inline void
+static inline int
 snd_pcm_indirect_capture_transfer(struct snd_pcm_substream *substream,
                                  struct snd_pcm_indirect *rec,
                                  snd_pcm_indirect_copy_t copy)
@@ -121,6 +124,8 @@ snd_pcm_indirect_capture_transfer(struct snd_pcm_substream *substream,
        if (diff) {
                if (diff < -(snd_pcm_sframes_t) (runtime->boundary / 2))
                        diff += runtime->boundary;
+               if (diff < 0)
+                       return -EINVAL;
                rec->sw_ready -= frames_to_bytes(runtime, diff);
                rec->appl_ptr = appl_ptr;
        }
@@ -147,6 +152,7 @@ snd_pcm_indirect_capture_transfer(struct snd_pcm_substream *substream,
                rec->hw_ready -= bytes;
                rec->sw_ready += bytes;
        }
+       return 0;
 }
 
 /*