Writing a driver for the Corsair K90 keyboard

[Clément Vuchener]

Thanks, I did not know about these lists. I see a leds mailing list too, 
I think I will split my backlight issue there.

> Maybe http://vger.kernel.org/vger-lists.html#linux-input ?
>
> On Mon, Aug 10, 2015 at 11:00 AM, Clément Vuchener
> <clement.vuchener at gmail.com> wrote:
>> It looks like no one had the answers to these questions. Is there a
>> better place to ask them?
>>
>>> Hello.
>>>
>>> I first sent this email to kernel-mentors, but I got no response. So I
>>> am sending it again here.
>>>
>>> I wrote a driver for the Corsair K90 keyboard, it is my first kernel
>>> development and I have a few questions about how to properly do a few
>>> things (mainly interactions with the user space).
>>>
>>> The Corsair Vengeance K90 is a mechanical keyboard with a backlight,
>>> macro keys (G1 to G18) and some other special keys (macro recording,
>>> profile switching, changing the light level or disabling the "windows
>>> logo" keys). The macro playback can be switched between hardware or
>>> software (from the driver not a key). Using the generic HID driver,
>>> the macro keys and special keys send wrong key code or no key code at
>>> all (because of the HID usage code used by the keyboard).
>>>
>>> The source for my driver can be found at this address:
>>> https://github.com/cvuchener/k90-linux-driver . It solves the problem
>>> of the generic driver and add some handling of the other features (see
>>> the README for more details).
>>>
>>> So, my questions are about:
>>>
>>> - Macro keys
>>> For handling the macro keys from a software, they need to send some
>>> keycodes but I have no idea what to use. Currently I use F keys above
>>> 12 and some MISC buttons and a parameter for changing that (at load
>>> time). Are there 18 keycodes reserved for custom uses? It would also
>>> be possible to send no keycode at all and use a specific software
>>> listening to the hidraw or hiddev devices, but I think it would be
>>> better to be able to use a generic software.
>>>
>>> - Backlight
>>> I chose to use a led class device to manage the backlight. It seems to
>>> work fine but when unregistering the driver, the light is set to 0.
>>> The keyboard remembers the previous light level and so nothing should
>>> be done when registering or unregistering the driver. Is the led class
>>> the right class for that? or am I using it wrong?
>>>
>>> - Sending the macro profiles to the keyboard
>>> I created a "profile" branch on my git repo for adding binary
>>> attributes used for sending macro data to the keyboard. But I am not
>>> sure it is a good idea, it may be better to leave that to the user space.
>>>
>>> Any other comment is welcome.
>>>
>>> Thanks,
>>> Clément
>>
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>