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Date:   Wed, 2 Feb 2022 09:38:51 +0100
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Subject: Re: [PATCH 0/4] drm/tiny: Add driver for Solomon SSD1307 OLED
 displays
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To:     Sam Ravnborg <sam@ravnborg.org>
Cc:     Geert Uytterhoeven <geert@linux-m68k.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux PWM List <linux-pwm@vger.kernel.org>,
        Linux Fbdev development list <linux-fbdev@vger.kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        Mark Brown <broonie@kernel.org>,
        DRI Development <dri-devel@lists.freedesktop.org>,
        Liam Girdwood <lgirdwood@gmail.com>,
        =?UTF-8?Q?Noralf_Tr=c3=b8nnes?= <noralf@tronnes.org>,
        Maxime Ripard <maxime@cerno.tech>,
        =?UTF-8?Q?Uwe_Kleine-K=c3=b6nig?= <u.kleine-koenig@pengutronix.de>,
        Thierry Reding <thierry.reding@gmail.com>,
        Lee Jones <lee.jones@linaro.org>,
        Peter Robinson <pbrobinson@gmail.com>
References: <20220131201225.2324984-1-javierm@redhat.com>
 <YfhM97cVH3+lJKg0@ravnborg.org> <Yfj/XGRRDNABsLPm@smile.fi.intel.com>
 <f8d71acb-5c8b-ac4e-0c32-38eb66af04c3@redhat.com>
 <CAMuHMdVP6ER119r2KAegjZes1a=KWZ47z6j=kgQ0oNx1oeUJ+w@mail.gmail.com>
 <51f54519-bb8b-f108-1c1e-4fed101ca5ef@redhat.com>
 <CAMuHMdVwUfv7pXhPazsgG6t=X=aVtDQkFUk_=mUuFH8Fscx8wg@mail.gmail.com>
 <abf63995-a529-1e80-18c3-df473a3e7a9c@redhat.com>
 <YfmaqUBqCrgp0QdO@ravnborg.org>
From:   Javier Martinez Canillas <javierm@redhat.com>
In-Reply-To: <YfmaqUBqCrgp0QdO@ravnborg.org>
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Hello Sam,

On 2/1/22 21:40, Sam Ravnborg wrote:

[snip]

> 
> I took a look at the datasheets - and all ssd1305, ssd1306 and ssd1307
> are the same. They have timing constrains on the Vcc.
> The random schematic I found on the net showed me that a PWM was used to
> control the Vcc voltage - which again is used to control the brightness.
> 
> All the above has nothing to do with backlight - I had this mixed up in
> my head.
>

Yes, same here. I was leaning towards fixing the DT binding but then due
Geert comment and after reading the datasheets for ssd130{5,6,7} like you
I had the same understanding.

Glad that you agree.

[snip] 

> 
> Last I recommend to drop the fbdev variant - if the drm driver has any
> regressions we can fix them. And I do not see any other way to move
> users over. Unless their setup breaks then they do not change.
>

As I mentioned in this thread I wouldn't propose to drop the fbdev variant.
I prefer to use the carrot and not the stick. Peter Robinson suggested to
make the driver mutually exclusive and add !FB_SSD1307 in the config symbol.

I think that makes sense and will do it in v2.

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