On 6/13/21 2:28 AM, Takashi Iwai wrote: > On Thu, 10 Jun 2021 22:53:24 +0200, > Pierre-Louis Bossart wrote: >> >> In case of mmap, by default alsa-lib mmaps both control and status data. >> >> If driver subscribes for application pointer update, driver needs to get >> notification whenever appl ptr changes. With the above case driver won't >> get appl ptr notifications. >> >> This patch check on a hw info flag and returns error when user land asks >> for mmaping control & status data, thus forcing user to issue >> IOCTL_SYNC_PTR. >> >> This patch was originally submitted in 2017, c.f. >> https://lore.kernel.org/alsa-devel/1494896518-23399-4-git-send-email-subhransu.s.prusty@xxxxxxxxx/ >> >> Suggested-by: Takashi Iwai <tiwai@xxxxxxx> >> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx> >> Reviewed-by: Kai Vehmanen <kai.vehmanen@xxxxxxxxxxxxxxx> >> Reviewed-by: Ranjani Sridharan <ranjani.sridharan@xxxxxxxxxxxxxxx> > > This kind of flag itself was what I also introduced for another > purpose, too. There is a WIP patch that allows the use of > non-coherent non-contiguous buffer pages, and this flag would fit for > that. FWIW, the patch is found at > https://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git/log/?h=topic/memalloc Sorry Takashi, I missed your feedback on this patch. Are you saying I should use the definition in that patch? +#define SNDRV_DMA_TYPE_NONCONTIG 8 /* non-coherent SG buffer */ I am not quite sure if how this is related to the application using mmap or not?
