[PATCH 1/7] ALSA: pcm: Fix negative appl_ptr handling in pcm-indirect helpers

Takashi Iwai
2017-05-21T19:02:52Z

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>
---
include/sound/pcm-indirect.h | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/sound/pcm-indirect.h b/include/sound/pcm-indirect.h
index 1df7acaaa535..7ade285328cf 100644
--- 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;
}

/*
--
2.13.0