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

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Date:	Tue, 12 May 2009 09:55:08 +0200
From:	Clemens Ladisch <clemens@...isch.de>
To:	David Fries <david@...es.net>
CC:	David Griffith <dgriffi@...csubak.edu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	todd@...es.net
Subject: Re: bad endpoint address, MOTU FastLane

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.


--- 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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