В Чт, 01/02/2024 в 13:51 +0100, Takashi Iwai пишет: > On Thu, 01 Feb 2024 12:53:08 +0100, > Alexander Tsoy wrote: > > > > For devices with multiple clock sources connected to a selector, we > > need > > to check what a clock selector control request has returned. This > > is > > needed to ensure that a requested clock source is indeed selected > > and for > > autoclock feature to work. > > > > For devices with single clock source connected, if we get an error > > there > > is nothing else we can do about it. We can't skip clock selector > > setup as > > it is required by some devices. So lets just ignore error in this > > case. > > > > This should fix various buggy Mackie devices: > > > > [ 649.109785] usb 1-1.3: parse_audio_format_rates_v2v3(): unable > > to find clock source (clock -32) > > [ 649.111946] usb 1-1.3: parse_audio_format_rates_v2v3(): unable > > to find clock source (clock -32) > > [ 649.113822] usb 1-1.3: parse_audio_format_rates_v2v3(): unable > > to find clock source (clock -32) > > > > There is also interesting info from the Windows documentation [1] > > (this > > is probably why manufacturers dont't even test this feature): > > > > "The USB Audio 2.0 driver doesn't support clock selection. The > > driver > > uses the Clock Source Entity, which is selected by default and > > never > > issues a Clock Selector Control SET CUR request." > > > > Link: > > https://learn.microsoft.com/en-us/windows-hardware/drivers/audio/usb-2-0-audio-drivers > > [1] > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=217314 > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=218175 > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=218342 > > Signed-off-by: Alexander Tsoy <alexander@xxxxxxx> > > --- > > sound/usb/clock.c | 10 +++++++++- > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > diff --git a/sound/usb/clock.c b/sound/usb/clock.c > > index a8204c6d6fac..60fcb872a80b 100644 > > --- a/sound/usb/clock.c > > +++ b/sound/usb/clock.c > > @@ -347,8 +347,16 @@ static int __uac_clock_find_source(struct > > snd_usb_audio *chip, > > !writeable) > > return ret; > > err = uac_clock_selector_set_val(chip, > > entity_id, cur); > > - if (err < 0) > > + if (err < 0) { > > + if (pins == 1) { > > + usb_audio_dbg(chip, > > + "%s(): > > selector returned an error, " > > + "assuming a > > firmware bug, id %d, ret %d\n", > > + __func__, > > clock_id, err); > > + return ret; > > + } > > return err; > > + } > > Hmm, what's the difference of the behavior except for the additional > debug message? Both returns ret, so I don't see how it fixes. If pins == 1, then ret is returned, otherwise err is returned. They are not equal here. But yes, the code is a bit confusing.
