Re: [PATCH 0/4] drm/tiny: Add driver for Solomon SSD1307 OLED displays

From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Javier Martinez Canillas <javierm@redhat.com>
Cc: "Sam Ravnborg" <sam@ravnborg.org>,
	"Geert Uytterhoeven" <geert@linux-m68k.org>,
	"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>,
	"Noralf Trønnes" <noralf@tronnes.org>,
	"Maxime Ripard" <maxime@cerno.tech>,
	"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	"Thierry Reding" <thierry.reding@gmail.com>,
	"Lee Jones" <lee.jones@linaro.org>,
	"Peter Robinson" <pbrobinson@gmail.com>
Subject: Re: [PATCH 0/4] drm/tiny: Add driver for Solomon SSD1307 OLED displays
Date: Wed, 2 Feb 2022 13:50:50 +0200	[thread overview]
Message-ID: <YfpwGtjj5hGkN7A4@smile.fi.intel.com> (raw)
In-Reply-To: <2f149fef-b991-9e34-98cb-426e561192ff@redhat.com>

On Wed, Feb 02, 2022 at 12:39:29PM +0100, Javier Martinez Canillas wrote:
> On 2/2/22 12:06, Andy Shevchenko wrote:
> > On Wed, Feb 02, 2022 at 09:38:51AM +0100, Javier Martinez Canillas wrote:
> >> On 2/1/22 21:40, Sam Ravnborg wrote:

> > And how will distros choose "the right" option in this case?
> 
> It depends on the distro. In Fedora we are disabling *all* the fbdev drivers.

Yes, and Distro A will think about old driver (because they have customers and
don't want to have a bad user experience) and Distro F will choose a new one.

> > What to do when I wan to see a regression and I want to change drivers w/o
> > recompilation?
> 
> If you want to have the two drivers without recompilation (and same compatible
> to match) then how would kmod / udev choose which one to load ? It becomes a
> race condition between the two drivers which one probes first.

We have a long history in kernel where new drivers came and old faded.
When two or more drivers of the same feature is enabled in the kernel
we may use modprobe facilities to prioritize them (blacklisting).

> > NAK from me to that proposal.
> 
> What's your suggestion then to solve the issue mentioned above ? With my distro
> maintainer hat I don't care that much, since the fbdev drivers will be disabled.

I think both of them can work together. If user doesn't care, the first one wins.

-- 
With Best Regards,
Andy Shevchenko