Extend device driver?

On Sat, Sep 10, 2016 at 08:58:07PM +0200, Pol Eyschen wrote:

On 10/09/16 17:14, Greg KH wrote:

quoted

On Sat, Sep 10, 2016 at 04:41:34PM +0200, Pol Eyschen wrote:

quoted

Hi everyone,

I want to implement some custom functions of my mouse (Madcatz RAT5) in
Linux, e.g custom DPI-values. As this requires writing over USB to the
firmware of the mouse I was thinking of writing a module to accomplish
this. However I don't want to reimplement a whole mouse-driver,so I
wanted to ask if there is a possibility of binding the device to 2
modules or having my module extend usbhid, so that my module would only
be used to perform these custom operations while usbhid stays in charge
of the whole "mouse business".

Please just use the hidraw userspace driver/library instead, that way
you don't have to unbind the kernel driver and everything should work
just fine without having to touch the kernel at all.

Hope this helps,

greg k-h

I looked at hidraw, unfortunately it doesn't work for me, as the mouse
expects control URBs with proprietary requests, hence my thought for a
kernel module.

Ok, then yes, you need to have a separate kernel driver.  Look at one of
the many examples of this in the kernel already, this is quite common.

For specific questions about this, I suggest asking on the linux-input
mailing list, as that is where the developers of this code live.

good luck!

greg k-h