linux-kernel - Re: [PATCH v4 1/4] pwm: pca9685: Switch to atomic API

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Message-ID: <CAGngYiUMP8P=8nEJu2weaR11PoZ9B2OGEdaz=DEeDsLoh3gmCw@mail.gmail.com>
Date:   Mon, 14 Dec 2020 11:27:40 -0500
From:   Sven Van Asbroeck <thesven73@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Clemens Gruber <clemens.gruber@...ruber.com>,
        linux-pwm@...r.kernel.org, Lee Jones <lee.jones@...aro.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        David Jander <david@...tonic.nl>
Subject: Re: [PATCH v4 1/4] pwm: pca9685: Switch to atomic API

Hi Thierry,

On Mon, Dec 14, 2020 at 9:28 AM Thierry Reding <thierry.reding@...il.com> wrote:
>
>
> Perhaps Clemens and Sven can shed some light into how this driver is
> being used. There clearly seem to be people interested in this driver,
> so why are there no consumers of this upstream. What's keeping people
> from upstreaming device trees that make use of this?
>

There are many reasons why a driver may not appear in the devicetree.
In my specific case, I backported the PCA9685 driver to a 4.1 Android vendor
kernel. This is too far behind to upstream. Also, the company regards the
devicetree as a trade secret, which it is entitled to do, as devicetrees
tend to be dual-licensed (GPL and MIT).

More generally, I believe that the PCA9685 is quite popular in the Raspberry
Pi world. Raspi devicetrees are not part of mainline, for various reasons
that we don't need to get into here.

Example:
https://learn.adafruit.com/adafruit-16-channel-servo-driver-with-raspberry-pi