USB low-speed bulk transfers

[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...

/* Steinar */
--
Homepage: http://www.sesse.net/
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

Relevant Pages

  • Re: HID Multitouch Digitiazer driver samples
    ... Set a breakpoint in your driver entry and AddDevice. ... I'm don't use bulk, because, somehow, the results are not so pleasing, maybe ... Suppose that I want to use USB isoc transfers, ... How is isoch traffic implemented on a serial communication? ...
    (microsoft.public.development.device.drivers)
  • Re: USB low-speed bulk transfers
    ... I recently bought an USB MIDI interface from ESI. ... Both endpoint descriptors are bulk. ... it looks like they are disallowed in the USB ... If I comment out the check, the driver works ...
    (Linux-Kernel)
  • Re: WinCe USB on Serial class problem
    ... i write a usb driver with serial class, ... there are too many bulk out nack between two bulk out ack ... used but i found is had limitation with wince usb host serial ... driver, only 64 byte in bulk out transfer,and how can i do to ...
    (microsoft.public.windowsce.platbuilder)
  • Re: HID Multitouch Digitiazer driver samples
    ... Set a breakpoint in your driver entry and AddDevice. ... I'm don't use bulk, because, somehow, the results are not so pleasing, maybe by the fact that i need to package the data in 16 packets with bulk and ony 4 with isochornous. ... it is a custom hid miniport and uses usb to talk to the device. ... How is isoch traffic implemented on a serial communication? ...
    (microsoft.public.development.device.drivers)
  • Need your advice on how to bind a MIDI virtual port to a USB driver
    ... I have a specific hardware connected to a PC through an USB to UART ... set of APIs that allow to manage the serial port without passing ... Actually I need to supply to the application level a MIDI virtual port, ... - I do not know anything about the USB client driver... ...
    (microsoft.public.development.device.drivers)
Loading