On Fri, 15 Oct 2021 21:59:30 +0200,
Pierre-Louis Bossart wrote:
>
> 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>
Reviewed-by: Takashi Iwai <tiwai@xxxxxxx>
thanks,
Takashi
> ---
> 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
>
