Re: Litra Glow on Linux

[Andreas Bergmeier <abergmeier@gmx.net>]

On Wed, 9 Nov 2022 at 21:27, Andreas Bergmeier <abergmeier@gmx.net> wrote:
>
> Finally I have an environment where I can test my kernel code.
>
> On Mon, 31 Oct 2022 at 10:29, Benjamin Tissoires
> <benjamin.tissoires@redhat.com> wrote:
> > For identifying the GLOW device you should be adding an id in the
> > table of hid-logitech-hidpp, with a driver data that tells the driver
> > to look for 0x1990.
> >
> > >
> > > > - you need to add a hook in connect_event to register the led class
> > > > device that will hook on to the actual LED of the device
> Sadly my tests did not go very far. The code fails already when
> calling the `probe` callback (`hidpp_probe`).
> When it calls into `hidpp_root_get_protocol_version` it seems to
> receive `HIDPP_ERROR_RESOURCE_ERROR`.
> Which then leads to an error message: Device not connected
> Upon looking at `HIDPP_ERROR_RESOURCE_ERROR` (9) there is no
> documentation what it means in code.
> From a look into the docs it says that 9 is UNSUPPORTED error for 2.0
> devices. Thus I am wondering how the code knows
> that it is a problem with connectivity. Couldn't it also mean that the
> device is not supporting getting the protocol version?
> And why is protocol version only enforced for non unifying devices?
Also, looking into `supported_reports` turned out to be 2 (very long).
Inside of `hidpp_root_get_protocol_version` it does upgrade SHORT to
LONG if the former is not supported.
On a whim I then added upgrade of LONG to VERY LONG if the former is
not supported. Sadly, the results stayed the same.