Re: [Libusb-devel] Patch: libusb/os/linux_usbfs.c: Distingush between usbfs and other kernel mode drivers

[Uwe B. <bo...@el...>]

>>>>> "Alan" == Alan Stern <st...@ro...> writes:

    Alan> On Wed, 6 Oct 2010, Xiaofan Chen wrote:
...
    >> If there is a kernel driver attached to the USB device (an
    >> interface), then libusb_claim_interface() should fail. And this is
    >> consistent with my view that "usbfs" is not a kernel driver in the
    >> context of libusb.

    Alan> If another program has claimed an interface, then
    Alan> libusb_claim_interface() _will_ fail.

But 
libusb_detach_kernel_driver()
libusb_claim_interface() 
will succeed.

It would be a good thing, if we could distinguish if the kernel driver is
usbfs or something else. For libftdi, we could unload ftdi_sio, that was
nearly always loaded when the device was plugged in, but stop the
application when some other libusb application already claimed the device.

Libusb-0 usb_get_driver_np() exposed the kernel driver name to the
user, libusb-1 doesn't. My proposed patch wouldn't reimplement
usb_get_driver_np but changed the return value of
libusb_kernel_driver_active(). But it was only a proposal,
libusb_kernel_driver_active() could perhaps also return the name.

This procedure has known races, but probably thats the price to pay for
user space versus a kernel driver.

Please let me know if I should work out the problem deeper. 

Bye
-- 
Uwe Bonnes                bo...@el...

Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt
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