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

[Xiaofan C. <xia...@gm...>]

On Wed, Oct 6, 2010 at 6:55 PM, Xiaofan Chen <xia...@gm...> wrote:
> On Wed, Oct 6, 2010 at 5:08 PM, Peter Stuge <pe...@st...> wrote:
>> Xiaofan Chen wrote:
>>> > It is really analogous to libusb0.sys in Windows.
>>>
>>> Totally different. If I need to use libusb0.sys, then I need to
>>> attach it to the device (as a device driver or a filter).
>>
>> Exactly the same! usbfs must be attached to the device (well, to the
>> interface) in order for libusb to work.
>>
>> The only difference is that Linux includes a generic USB driver
>> (usbfs) already and Windows does not, and that when calling
>> libusb_claim_interface() on Linux the driver is bound to the
>> interface by the kernel. Windows binds the driver much more
>> statically.
>>
>
> Okay this is a good point and I can agree with you it is
> a kernel driver after all, albeit a generic one.
>
> However, let's go back to the context of libusb. Say,
> for libusb-0.1, what do you expect to return for the
> usb_get_driver_np()?
> http://libusb.sourceforge.net/doc/ref.nonportable.html
>
> The typical code to call usb_detach_kernel_driver_np()
> is to call usb_get_driver_np() first to see if there are
> another driver is attached to the interface. If the existing
> kernel driver (not usbfs) is already detached, you do
> not need to detach the kernel driver.
>
> Similar for libusb-1.0, I expect libusb_kernel_driver_active
> to return one is only usbfs is bound to the interface.

Typo. I expect  libusb_kernel_driver_active to return 0
if only "usbfs" is bound to the interface.

    0 if no kernel driver is active
    1 if a kernel driver is active
    LIBUSB_ERROR_NO_DEVICE if the device has been disconnected
    another LIBUSB_ERROR code on other failure

> http://libusb.sourceforge.net/api-1.0/group__dev.html#ga76e047ca95da2b32d0e7455da1804a49
> And it is clear not the intention of libusb developers
> to ask the user to attach the "usbfs" driver to the interface
> for the libusb_attach_kernel_driver().
>
> So my conclusion is still "usbfs" kernel driver is
> equivalent to no kernel driver in the context of libusb.
>
> Daniel: if I am wrong, please point out. Thanks.
>



-- 
Xiaofan