Re: USB low-speed bulk transfers
Andrew Morton <[email protected]>
| Newsgroups | gmane.linux.usb.devel,gmane.linux.kernel |
|---|---|
| Message-ID | <[email protected]> |
On Wed, 6 Jun 2007 23:20:46 +0200 "Steinar H. Gunderson" <[email protected]> wrote: > [Please Cc on reply] > > Hi, > > I recently bought an USB MIDI interface from ESI (called “ESI MIDI Mate”). It > claims to work with Linux, but doesn't -- I've already asked the manufacturer > for an explanation, but as I was impatient, I hacked a bit on the drivers to > actually make it work... > > The /proc/bus/usb/devices entry looks like this: > > T: Bus=04 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#= 4 Spd=1.5 MxCh= 0 > D: Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS= 8 #Cfgs= 1 > P: Vendor=0a92 ProdID=1001 Rev= 1.04 > S: Manufacturer=ESI > S: Product=ESI MIDI Mate > C:* #Ifs= 2 Cfg#= 1 Atr=80 MxPwr= 20mA > I:* If#= 0 Alt= 0 #EPs= 0 Cls=01(audio) Sub=01 Prot=00 Driver=snd-usb-audio > I:* If#= 1 Alt= 0 #EPs= 2 Cls=01(audio) Sub=03 Prot=00 Driver=snd-usb-audio > E: Ad=81(I) Atr=02(Bulk) MxPS= 4 Ivl=0ms > E: Ad=01(O) Atr=02(Bulk) MxPS= 4 Ivl=0ms > > There are two points worth noting here: > > - The device is USB low speed. snd-usb-audio simply checks for full/high > speed, and refuses any device that isn't. I can hack around this, > inverting a few checks etc., and it seems to work reasonably well > (probably since the device has no PCM parts). > - Both endpoint descriptors are bulk. The HCD driver plain refuses bulk > transfers for low-speed; it looks like they are disallowed in the USB > standard somehow. If I comment out the check, the driver works > (perfectly!), but I guess this isn't acceptable for upstream? > > Could the check for low-speed bulk transfers be replaced by a kernel warning > somehow? I can't see any big harm by allowing them, and obviously, Windows XP > and Mac OS X does so. > > I can supply a patch for the snd-usb-audio specific parts if desired, but I > can't guarantee it's the correct fix for cards that support PCM. Not that I > know of any PCM-capable low-speed USB sound cards out there... > (added linux-usb-devel to cc) ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel