From b456abe63f60ad93c83a526d33b71574bc32656c Mon Sep 17 00:00:00 2001 From: Pierre-Louis Bossart Date: Fri, 19 Nov 2021 17:08:50 -0600 Subject: ALSA: pcm: introduce INFO_NO_REWINDS flag 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 Reviewed-by: Takashi Iwai Reviewed-by: Ranjani Sridharan Reviewed-by: Kai Vehmanen Signed-off-by: Pierre-Louis Bossart Link: https://lore.kernel.org/r/20211119230852.206310-3-pierre-louis.bossart@linux.intel.com Signed-off-by: Mark Brown --- sound/core/pcm_lib.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'sound/core') diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c index fdd992772b20..f2090025236b 100644 --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -2128,6 +2128,7 @@ 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) @@ -2135,6 +2136,19 @@ 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) { -- cgit v1.2.3