Re: [PATCH AUTOSEL 5.4 057/130] ALSA: usb-audio: Check valid altsetting at parsing rates for UAC2/3

[Sasha Levin]

On Wed, Dec 23, 2020 at 08:09:41AM +0100, Takashi Iwai wrote:
> On Wed, 23 Dec 2020 03:17:00 +0100,
> Sasha Levin wrote:
> > From: Takashi Iwai <tiwai@xxxxxxx>
> >
> > [ Upstream commit 93db51d06b32227319dae2ac289029ccf1b33181 ]
> >
> > The current driver code assumes blindly that all found sample rates for
> > the same endpoint from the UAC2 and UAC3 descriptors can be used no
> > matter which altsetting, but actually this was wrong: some devices
> > accept only limited sample rates in each altsetting.  For determining
> > which altsetting supports which rate, we need to verify each sample rate
> > and check the validity via UAC2_AS_VAL_ALT_SETTINGS.  This control
> > reports back the available altsettings as a bitmap.
> >
> > This patch implements the missing piece above, the verification and
> > reconstructs the sample rate tables based on the result.
> >
> > An open question is how to deal with the altsettings that ended up
> > with no valid sample rates after verification.  At least, there is a
> > device that showed this problem although the sample rates did work in
> > the later usage (see bug link).  For now, we accept such an altset as
> > is, assuming that it's a firmware bug.
> >
> > Reported-by: Dylan Robinson <dylan_robinson@xxxxxxxx>
> > Tested-by: Keith Milner <kamilner@xxxxxxxxxxxxxxx>
> > Tested-by: Dylan Robinson <dylan_robinson@xxxxxxxx>
> > BugLink: https://bugzilla.suse.com/show_bug.cgi?id=1178203
> > Link: https://lore.kernel.org/r/20201123085347.19667-4-tiwai@xxxxxxx
> > Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
>
> Please drop this for 5.4 or older.  At least this caused some problem
> on 5.3 kernel that confused USB core by some reason while it works
> fine with the recent upstream.

Will do, thanks.

--
Thanks,
Sasha