On Thu, 12 Aug 2021 20:37:06 +0200, Pierre-Louis Bossart wrote: > > > Hi Takashi, > > > 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. > > > > 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. > > This looks like the same functionality as in the patch "ALSA: pcm: > conditionally avoid mmap of control data" that we submitted for the SPIB > support, no? Yes, quite similar. That's what I mentioned in the reply at that time. > I was about to resubmit a v2 based on my version (code was reviewed on > GitHub in https://github.com/thesofproject/linux/pull/3076). > > If it's the same solution, could this patch be applied first so we are > aligned regardless of the order in which memalloc and SPIB patches are > merged? The renaming is fine, and that was your idea that I implemented > anyways. > > I think there would be a need for a tag as well so that Mark's tree > compiles when the SOF driver uses this. Sure, I can merge this one with a slight more rewording. thanks, Takashi
