Martin Langer wrote:
> my new USB-MIDI-Keyboard has two USB subclasses usb-midi and usb-audio.
> Evolution, the manufacturer, told me "it's an Audio Class compliant device",
> but I don't find a new entry in /proc/asound/seq/clients after loading the
> modules.
>
> usb.c: registered new driver snd-usb-midi
> snd-usb-midi: using interface 1
> snd-usb-midi: MIDIStreaming version 01.00
> snd-usb-midi: using 1 input jack(s) on endpoint 1
> snd-usb-midi: using 1 output jack(s) on endpoint 2
> snd-usb-midi: detected Evolution Electronics L MK-249C USB MIDI keyboa
> usb.c: snd-usb-midi driver claimed interface dfe688d8
>
> It's not typical to have a midi-keyboard with two subclasses, or?
As Pedro said, subclass 1 is an AudioControl interface. There should be
two cards, one created by snd-usb-audio, and the other one created by
snd-usb-midi (see /proc/asound/cards). The contents of the control
interface (if there are any controls) should be visible in the output
of the "lsusb" command.
Your keyboard is unusual in two respects: it's an Audio Class compliant
device (yes, this _is_ unusual for USB MIDI devices :-) , and it uses
two endpoints, one for each direction. The combination of these two
triggers an ugly bug in the descriptor parsing code (device_info isn't
initialized).
Please try the following patch (the current taciturnity of the driver
is somewhat inconvenient, so it adds some error messages as well).
Index: usb/usbmidi.c
===================================================================
RCS file: /cvsroot/alsa/alsa-driver/usb/usbmidi.c,v
retrieving revision 1.4
diff -u -r1.4 usbmidi.c
--- usb/usbmidi.c 5 Jul 2002 13:39:28 -0000 1.4
+++ usb/usbmidi.c 30 Jul 2002 12:39:00 -0000
@@ -834,8 +834,10 @@
port = snd_seq_event_port_attach(umidi->seq_client,
&port_callback,
cap, type, port_name);
- if (port < 0)
+ if (port < 0) {
+ snd_printk(KERN_ERR "cannot create port (error code %d)\n",
+err);
return port;
+ }
if (in)
umidi->endpoints[ep].in->ports[c].seq_port = port;
@@ -1084,6 +1086,8 @@
usb_ms_endpoint_descriptor_t* ms_ep;
int i, epidx;
+ memset(device_info, 0, sizeof(*device_info));
+
if (usb_device->descriptor.iManufacturer == 0 ||
usb_string(usb_device, usb_device->descriptor.iManufacturer,
device_info->vendor, sizeof(device_info->vendor)) < 0)
@@ -1180,12 +1184,15 @@
{
usbmidi_device_info_t device_info;
snd_card_t* card = NULL;
+ int err;
if (snd_usbmidi_get_device_info(device, ifnum, device_id,
&device_info) == 0) {
printk(KERN_INFO "snd-usb-midi: detected %s %s\n",
device_info.vendor, device_info.product);
- snd_usbmidi_card_create(device, &device_info, &card);
+ err = snd_usbmidi_card_create(device, &device_info, &card);
+ if (err < 0)
+ snd_printk(KERN_ERR "cannot create card (error code %d)\n",
+err);
}
return card;
}
> ... and doing rmmod snd-usb-midi and rmmod snd-usb-audio ends here with
> Segmentation fault:
>
> Jul 28 22:28:10 tuba kernel: usb.c: deregistering driver snd-usb-midi
> Jul 28 22:28:10 tuba kernel: Unable to handle kernel paging request at
> virtual address 29323034
>
> a small bug or a big hole?
A small bug which results in a big mess.
HTH
Clemens
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