On Fri, 13 Aug 2021 10:21:42 +0200, Takashi Iwai wrote: > > ALSA PCM core has an optimized way to communicate with user-space for > its control and status data via mmap on the supported architectures > like x86. Depending on the situation, however, we'd rather want to > enforce user-space notifying the applptr or hwptr change explicitly > via ioctl. For example, the upcoming non-contig and non-coherent > buffer handling would need an explicit sync, and this needs to catch > the applptr and hwptr changes. Also, ASoC SOF driver will have the > SPIB support that has the similar requirement for the explicit control > of the applptr and hwptr. > > This patch adds the new PCM hardware info flag, > SNDRV_PCM_INFO_EXPLICIT_SYNC. When this flag is set, PCM core > disables both the control and the status mmap, which enforces > user-space to update via SYNC_PTR ioctl. In that way, drivers can > catch the applptr and hwptr update and apply the sync operation if > needed. > > Link: https://lore.kernel.org/r/20210812113818.6479-1-tiwai@xxxxxxx > Link: https://lore.kernel.org/r/20210610205326.1176400-1-pierre-louis.bossart@xxxxxxxxxxxxxxx > Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> Now merged to for-next branch. Takashi
