On Mon, Aug 22, 2022 at 04:06:58PM +0800, chihhao chen wrote:
> I am testing many headsets on Android platform with different kernel
> versions.
>
> On kernel-5.10, calling sequence for playback is
> 1. snd_usb_hw_params -> set highest sampling rate, no
> SAMPLING_FREQ_CONTROL USB request sent in this stage
> 2. snd_pcm_release
> 3. snd_usb_hw_params -> set proper sampling rate, still no
> SAMPLING_FREQ_CONTROL USB request
> 4. snd_usb_pcm_parepare -> in configure_endpoint SAMPLING_FREQ_CONTROL
> USB request was sent on USB bus
>
> With the same calling sequence, a slightly behavior change on kernel-
> 5.15 is
> 1. snd_usb_hw_params -> set highest sampling rate,
> SAMPLING_FREQ_CONTROL USB request was sent on USB bus
> 2. snd_pcm_release
> 3. snd_usb_hw_params -> set proper sampling rate, SAMPLING_FREQ_CONTROL
> USB request was sent too
> (because configure_endpoint was moved to snd_usb_hw_params function)
> 4. snd_usb_pcm_parepare -> no SAMPLING_FREQ_CONTROL USB
> request because of USB EP flag check
>
> I checked all USB packets and confirmed audio data output was correct.
> But there may be missing sound problem for the first sound with many
> headsets (for example Samsung headset).
> I found this issue is related to two-times sampling rate set request.
> (I tried to forcibly skip first USB request, everything became okay.)
> So do you guys know why configure_endpoint was moved to
> snd_usb_hw_params?
Hi Chihhao,
the commit you're looking for is bf6313a0ff766925462e97b4e733d5952de02367
("ALSA: usb-audio: Refactor endpoint management")
Good luck,
Geraldo Nascimento
> Or could you provide patch for this problem?
>
> Many thanks
> Chihhao
>
