[alsa-devel] Question about tsched=0 on PulseAudio

[Kuninori Morimoto]

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