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Date:   Mon, 20 Dec 2021 12:30:32 +0100
From:   Johan Hovold <johan@kernel.org>
To:     Oliver Neukum <oneukum@suse.com>
Cc:     Ralf Beck <musical_snake@gmx.de>, linux-usb@vger.kernel.org
Subject: Duplicate endpoints (was: Re:)
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On Mon, Dec 20, 2021 at 11:01:56AM +0100, Oliver Neukum wrote:
> 
> On 20.12.21 07:46, Ralf Beck wrote
> > One set with audio class specific interfaces for use by an audi
> > class driver.  The other set with vendor specific interfaces for use
> > by the vendor driver.  Obviously the class specific interfaces and
> > vendor specific interfaces are not intended to be use by a driver
> > simultaniously.

> Such devices are buggy. We usually define quirks for such devices.

> > There must be another solution to deal with this. It is unacceptable
> > to request a user of these devices to have to disablethe duplicate
> > endpoint check and recompile the kernel on every update in order to
> > be able to use their devices in vendor mode.

> I suggest you write a patch to introduce a quirk that disables one of the
> interfaces and disregards disabled interfaces for purposes of the check.

We already have USB_QUIRK_ENDPOINT_IGNORE (previously known as
USB_QUIRK_ENDPOINT_BLACKLIST) for this. See, for example:

	184eead057cc ("USB: core: Fix regression in Hercules audio card")

and

	bdd1b147b802 ("USB: quirks: blacklist duplicate ep on Sound Devices USBPre2")

Johan