Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <ce3adf7013ba01aad54fb65bf9c657dd9d0b7d23.camel@hadess.net>
Subject: Re: [PATCH] HID: logitech-hidpp: support Color LED feature (8071).
From:   Bastien Nocera <hadess@hadess.net>
To:     Filipe =?ISO-8859-1?Q?La=EDns?= <lains@riseup.net>,
        Manuel =?ISO-8859-1?Q?Sch=F6nlaub?= <manuel.schoenlaub@gmail.com>
Cc:     jikos@kernel.org, benjamin.tissoires@redhat.com,
        linux-input@vger.kernel.org, linux-kernel@vger.kernel.org
Date:   Wed, 23 Mar 2022 23:24:18 +0100
In-Reply-To: <275245e8048fa124055d9ff3d10ce6562294483a.camel@riseup.net>
References: <Yifr4etBFPu1a2Ct@hermes>
         <275245e8048fa124055d9ff3d10ce6562294483a.camel@riseup.net>
Content-Type: text/plain; charset="UTF-8"
User-Agent: Evolution 3.42.4 (3.42.4-1.fc35) 
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

On Wed, 2022-03-23 at 21:22 +0000, Filipe Laíns wrote:
> On Tue, 2022-03-08 at 16:50 -0700, Manuel Schönlaub wrote:
> > The HID++ protocol allows to set multicolor (RGB) to a static
> > color.
> > Multiple of such LED zones per device are supported.
> > This patch exports said LEDs so that they can be set from
> > userspace.
> > 
> > Signed-off-by: Manuel Schönlaub <manuel.schoenlaub@gmail.com>
> > ---
> >  drivers/hid/hid-logitech-hidpp.c | 188
> > +++++++++++++++++++++++++++++++
> >  1 file changed, 188 insertions(+)
> 
> *snip*
> 
> Hi Manuel,
> 
> Thanks for putting this forward, although I am not sure if this is
> the best way
> to handle this.
> 
> Before anything, could you elaborate a bit on what lead to you
> wanting this?
> 
> There are a couple of reasons why merging this in the kernel might be
> problematic.
> 
> 1) I don't think we will ever support the full capabilities of the
> devices, so
> configuration via userspace apps will always be required, and here we
> are
> introducing a weird line between the two.
> 
> 2) There is already an ecosystem of userspace configuration apps,
> with which
> this would conflict. They might not be in the best maintenance state
> due to lack
> of time from the maintainers, but moving this functionality to the
> kernel, which
> is harder change, and harder to ship to users, will only make that
> worse.

There's already an API for LEDs in the kernel, why shouldn't it be used
to avoid user-space needing to know how to configure Logitech, and
every other brand of keyboards?

systemd has code to save and restore LED status, as well as code to
change the level of backlight. I can imagine that it wouldn't take much
to make it aware of RGB LEDs so it handles them properly, whether it's
for Logitech, or another brand of keyboards, or laptops.