When the hardware can only deal with a monotonically increasing
appl_ptr, this flag can be set.
In case the application requests a rewind, be it with a
snd_pcm_rewind() or with a direct change of a mmap'ed pointer followed
by a SNDRV_PCM_IOCTL_SYNC_PTR, this patch checks if a rewind
occurred and returns an error.
Credits to Takashi Iwai for identifying the path with SYNC_PTR and
suggesting the pointer checks.
Suggested-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@xxxxxxxxxxxxxxx>
Reviewed-by: Kai Vehmanen <kai.vehmanen@xxxxxxxxx>
---
include/uapi/sound/asound.h | 2 +-
sound/core/pcm_lib.c | 14 ++++++++++++++
2 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h
index 5859ca0a1439..59fcf39f022e 100644
--- a/include/uapi/sound/asound.h
+++ b/include/uapi/sound/asound.h
@@ -300,7 +300,7 @@ typedef int __bitwise snd_pcm_subformat_t;
#define SNDRV_PCM_INFO_HAS_LINK_ESTIMATED_ATIME 0x04000000 /* report estimated link audio time */
#define SNDRV_PCM_INFO_HAS_LINK_SYNCHRONIZED_ATIME 0x08000000 /* report synchronized audio/system time */
#define SNDRV_PCM_INFO_EXPLICIT_SYNC 0x10000000 /* needs explicit sync of pointers and data */
-
+#define SNDRV_PCM_INFO_NO_REWINDS 0x20000000 /* hardware can only support monotonic changes of appl_ptr */
#define SNDRV_PCM_INFO_DRAIN_TRIGGER 0x40000000 /* internal kernel flag - trigger in drain */
#define SNDRV_PCM_INFO_FIFO_IN_FRAMES 0x80000000 /* internal kernel flag - FIFO size is in frames */
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index ec53a3e7cf35..1d3927aa3dd8 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -2127,6 +2127,7 @@ int pcm_lib_apply_appl_ptr(struct snd_pcm_substream *substream,
{
struct snd_pcm_runtime *runtime = substream->runtime;
snd_pcm_uframes_t old_appl_ptr = runtime->control->appl_ptr;
+ snd_pcm_sframes_t diff;
int ret;
if (old_appl_ptr == appl_ptr)
@@ -2134,6 +2135,19 @@ int pcm_lib_apply_appl_ptr(struct snd_pcm_substream *substream,
if (appl_ptr >= runtime->boundary)
return -EINVAL;
+ /*
+ * check if a rewind is requested by the application
+ */
+ if (substream->runtime->info & SNDRV_PCM_INFO_NO_REWINDS) {
+ diff = appl_ptr - old_appl_ptr;
+ if (diff >= 0) {
+ if (diff > runtime->buffer_size)
+ return -EINVAL;
+ } else {
+ if (runtime->boundary + diff > runtime->buffer_size)
+ return -EINVAL;
+ }
+ }
runtime->control->appl_ptr = appl_ptr;
if (substream->ops->ack) {
--
2.25.1
