Re: [Libusb-devel] default drivers for usb devices

[Johannes E. <joh...@er...>]

On Wed, Oct 23, 2002, Bhanu Nagendra P. <bpi...@cs...> wrote:
> I have a Xilinx XSV board with a basic core on it which provides a bulk
> endpoint. I am using libusb to get a handle to the deivce and send bulk
> messages to it, which all works fine.
> 
> I am interested in understanding the working of libusb. When I tried
> handtracing the call to usb_bulk_write() in program, I figured out that it
> boils down
> to a call in linux.c, which reads:
> ret=ioctl(dev->fd, IOCTL_USB_BULK,&bulk);
> 
> fd is a file descriptor which points to the file /proc/bus/usb/001/002-
> which corresponds to my XSV board.
> 
> Given that my board has no custom driver associated with it, I am
> unable to
> fgiure out as to where the above ioctl is being implemented. I tried
> doing a search on IOCTL_USB_BULK in the source for for the libusb and
> kernel but did not find any occurences of implementation.

drivers/usb/devio.c

We use a different name in libusb than the kernel uses.

> The other related question I had is that there are no device numbers
> associated with that device:
> ls -l /proc/bus/usb/001/002
> does not list 002 as any special type of file (as opposed to   character
> or block devices).
> 
> With this being the case, how is the kernel able to recognize this as a
> usb device file and treat it accordingly -i.e- associate a 'special'
> driver for it?

/proc/bus/usb is a virtual filesystem called usbdevfs (usbfs under newer
kernels). That's why they don't show up as device nodes. They are just
virtual files.

JE