On Tue, 8 Jan 2008, Takashi Iwai wrote: > At Tue, 8 Jan 2008 10:45:34 +0100 (CET), > Jaroslav Kysela wrote: > > > > Hi, > > > > it seems that we have another inconsistency with PCM MMAP mode > > timestamps. If I read code correctly, snd_pcm_status() returns timestamp > > from last interrupt BUT updates hw_ptr to current (calling > > snd_pcm_update_hw_ptr() again). > > It means, that application will get unrelated timestamp to > > hw position returned in snd_pcm_status() in case of mmap mode. I don't see > > any way to use this timestamp now. > > To fix this issue, I would like to create a next status ioctl > > which will return only mmap timestamp plus last related interrupt ring > > buffer position and remove 'if (runtime->tstamp_mode == > > SNDRV_PCM_TSTAMP_MMAP)' condition from snd_pcm_status() in driver > > completely. > > Any opinion? Other idea? > > It'd be OK to remove the tstamp_mode check there. It was newly added > after discussions. We are still in the development phase about this, > and removing is no regression. > > However, I'm against adding new ioctls. The same thing can be simply > done by reading the mmapped status struct, as snd_pcm_hw_fast_tstamp() > in alsa-lib pcm_hw.c. If the mmaped status isn't available, it can > fallback to the normal snd_pcm_status(). You're right. I forgot on mmaped status and PCM_IOCTL_SYNC_PTR for non-mmap architectures. > The real problem is that the behavior of TSTAMP_MMAP isn't strictly > defined. It's just a TSTAMP_NORMAL in the end unless the new if check > there. I think we may get rid of this mode if the tstamp via mmap is > available. Actually, after condition removal, TSTAMP_MMAP will just enable timestamping in interrupt update. No other tests are in the driver. I commited change to HG. Jaroslav ----- Jaroslav Kysela <perex@xxxxxxxx> Linux Kernel Sound Maintainer ALSA Project, Red Hat, Inc. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
