linux-kernel - Re: [PATCH v3 3/7] drm: Add driver for Solomon SSD130X OLED displays

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Message-ID: <600f0f72-4af8-1c43-33a5-a0b5ef97c3c7@redhat.com>
Date:   Wed, 9 Feb 2022 16:17:01 +0100
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     linux-pwm@...r.kernel.org, linux-fbdev@...r.kernel.org,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Liam Girdwood <lgirdwood@...il.com>,
        Noralf Trønnes <noralf@...nnes.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Maxime Ripard <maxime@...no.tech>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
        Thierry Reding <thierry.reding@...il.com>,
        Lee Jones <lee.jones@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Sam Ravnborg <sam@...nborg.org>
Subject: Re: [PATCH v3 3/7] drm: Add driver for Solomon SSD130X OLED displays

On 2/9/22 16:03, Mark Brown wrote:
> On Wed, Feb 09, 2022 at 03:50:13PM +0100, Javier Martinez Canillas wrote:

[snip]

> 
>> But I understand why the Device Tree binding and fbdev driver used VBAT
>> since that's what the documentation mentions.
> 
> What is "the documentation" in this context and how is that distinct
> from the datasheet for the display controller?  In general the consumer
> driver should be using the name from the datasheet and the regulator
> itself should get a regulator-name reflecting the name in the schematic.
>

For "documentation" I meant the datasheet that mentions VBAT but I got
what you mean and will also propose a change to the binding to rename
the property to vcc-supply instead to match the pin name in the device.

>>> It is depressingly common to see broken code here, unfortunately
>>> graphics drivers seem like one of the most common offendors.
> 
>> I'll include a patch for the existing DT binding and mark the vbat-supply
>> property as required. Probably we won't be able to change the fbdev driver
>> without causing regressions, and I'm not interested in that driver anyways.
> 
> There should be little danger of causing regressions given that a dummy
> regualtor will be provided when one is missing.

Right, I forgot that a dummy regulator is provided in that case. Perfect.

Best regards,
-- 
Javier Martinez Canillas
Linux Engineering
Red Hat