linux-kernel - Re: bad endpoint address, MOTU FastLane

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Message-ID: <20090524220756.GC4300@spacedout.fries.net>
Date:	Sun, 24 May 2009 17:07:56 -0500
From:	David Fries <david@...es.net>
To:	Clemens Ladisch <clemens@...isch.de>
Cc:	David Griffith <dgriffi@...csubak.edu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alan Stern <stern@...land.harvard.edu>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: bad endpoint address, MOTU FastLane

On Tue, May 12, 2009 at 09:55:08AM +0200, Clemens Ladisch wrote:
> David Fries wrote:
> > usb_submit_urb returns -22 EINVAL invalid argument as it is trying to
> > submit an interrupt packet to what is registered as an isoc endpoint.
> > The second interface has the same end point addresses as the first.
> > Any suggestions on how to deal with this class of broken hardware?
> > 
> > I:* If#= 0 Alt= 0 ...
> > E:  Ad=81(I) Atr=03(Int.) MxPS=   4 Ivl=1ms
> > I:* If#= 1 Alt= 0 ...
> > E:  Ad=81(I) Atr=01(Isoc) MxPS=   4 Ivl=1ms
> 
> AFAICS the USB core memorizes the descriptor belonging to a specific
> endpoint number whenever usb_set_interface() is called.  In this case,
> the second interface is initialized later, so the second set of
> descriptors wins.
> 
> The driver could call usb_set_interface() again for the first interface
> so that the USB core takes notice of the first set of endpoints again.
> Please try the patch below.
> 
> I guess I'll have to write another quirk for this.

Thanks for the quick response, sorry for taking so long to test it.
Adding usb_set_interface lets the device work again, I had been
tracking this down for a while, I'm glad you knew what to do.

The MOTU Fastlane device is the only one using QUIRK_MIDI_RAW.  How about
changing the name to QUIRK_MIDI_FASTLANE to imply it isn't completely
generic anymore and adding a comment?  I can write up that patch if
it's agreeable.  The only danger I see is if there are some MOTU
Fastlane devices with a corrected descriptor record, but if that were
the case setting it to the 0 alternative setting would be a no-op in
that case, so it sounds good to me.

	case QUIRK_MIDI_FASTLANE:
		/* MOTU Fastlane has two interfaces with the second
		 * interface reusing the endpoint addresses voilating
		 * the standard.  Select interface 0 again to reload
		 * that configuration.
		 */
		usb_set_interface(umidi->chip->dev, 0, 0);
		umidi->usb_protocol_ops = &snd_usbmidi_raw_ops;
		err = snd_usbmidi_detect_per_port_endpoints(umidi, endpoints);
		break;

> --- linux/sound/usb/usbmidi.c
> +++ linux/sound/usb/usbmidi.c
> @@ -1779,6 +1779,7 @@
>  		err = snd_usbmidi_detect_per_port_endpoints(umidi, endpoints);
>  		break;
>  	case QUIRK_MIDI_RAW:
> +		usb_set_interface(umidi->chip->dev, 0, 0);
>  		umidi->usb_protocol_ops = &snd_usbmidi_raw_ops;
>  		err = snd_usbmidi_detect_per_port_endpoints(umidi, endpoints);
>  		break;
> --
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-- 
David Fries <david@...es.net>
http://fries.net/~david/ (PGP encryption key available)
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