USB: Fix configuration selection issues introduced in v4.20.0

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Tue, Jan 15, 2019 at 07:13:54PM +0300, Nikolay Yakimov wrote:
> Commit f13912d3f014a introduced changes to the usb_choose_configuration function
> to better support USB Audio UAC3-compatible devices. However, there are a few
> problems with this patch. First of all, it adds new "if" clauses in the middle
> of an existing "if"/"else if" tree, which obviously breaks pre-existing logic.
> Secondly, since it continues iterating over configurations in one of the branches,
> other code in the loop can choose an unintended configuration. Finally,
> if an audio device's first configuration is UAC3-compatible, and there
> are multiple UAC3 configurations, the second one would be chosen, due to
> the first configuration never being checked for UAC3-compatibility.
> 
> Commit ff2a8c532c14 tries to fix the second issue, but it goes about it in a
> somewhat unnecessarily convoluted way, in my opinion, and does nothing
> to fix the first or the last one.
> 
> This patch tries to rectify problems described by essentially rewriting
> code introduced in f13912d3f014a. Notice the code was moved to *before*
> the "if"/"else if" tree.
> 
> Signed-off-by: Nikolay Yakimov <root@livid.pp.ru>
> ---
>  drivers/usb/core/generic.c | 44 ++++++++++++++++++++++----------------
>  1 file changed, 25 insertions(+), 19 deletions(-)

Were you able to test this on one of the devices that ff2a8c532c14
("usbcore: Select only first configuration for non-UAC3 compliant
devices") was created to fix?

thanks,

greg k-h