Hi Takashi-san # Oops !? # You and Iwai-san are both same name :) > > OK, thank you for your explanation. > > My current driver updates snd_pcm_ops::pointer only when DMA transfer was > > finished, but I guess it needs to adjust to update it during transfer, too. > > I think I can use dmaengine_tx_status() for this purpose. > > I don't know how to know about delay, but I will try update pointer as 1st step. > > If your driver calls 'snd_pcm_period_elapsed()' in any hw/sw IRQ > context, it's correct. But 'struct snd_pcm_ops.pointer' callback is > not only executed by the function, but also in the other contexts such > as ioctl(2) with HWSYNC. > > In design of ALSA PCM core, the callback is expected to return the > number of PCM frames currently transferred via physical audio serial > bus, inner PCM period boundary. As long as I know, recent hardwares > have any register for this purpose and your driver could calculate the > number. > > The 'accuracy' represents how accurate the returned number is, against > actual transferring via audio serial bus. Thank you for your detail explanation. I will adjust my driver Best regards --- Kuninori Morimoto _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
