At Fri, 09 Jan 2015 09:48:42 +0100, Clemens Ladisch wrote:
Paul Bonser wrote:
On 01/08/2015 03:56 PM, Clemens Ladisch wrote:
Paul Bonser wrote:
The Akai MPC Element incorrectly reports its bInterfaceClass as 255, but otherwise implements the USB MIDI spec correctly.
This adds a quirks-table.h entry which allows the device to be recognized as a standard USB MIDI device.
+++ b/sound/usb/quirks-table.h +{
- /* Akai MPC Element */
- USB_DEVICE(0x09e8, 0x0021),
- .driver_info = (unsigned long) & (const struct snd_usb_audio_quirk) {
.ifnum = QUIRK_ANY_INTERFACE,.type = QUIRK_COMPOSITE,.data = & (const struct snd_usb_audio_quirk[]) {{.ifnum = 0,.type = QUIRK_IGNORE_INTERFACE},{.ifnum = 1,.type = QUIRK_MIDI_STANDARD_INTERFACE},{.ifnum = -1}}- }
+},
Why a composite quirk? Does a single quirk entry not work?
A single quirk entry results in an error message in dmesg: "snd-usb-audio: probe of 3-2:1.0 failed with error -5"
That message is normal for unhandled interfaces.
It's still not good to show a message, so using QUIRK_IGNORE_INTERFACE is good enough as a workaround. So I applied it as is to for-next branch now. Though...
Does it actually prevent the device from working?
... it's still interesting why it needs a special handling. If we find out more and have a better fix, let's put on top of the current patch.
thanks,
Takashi