linux-kernel - Re: [RFC PATCH 0/3] staging: remove fbdev drivers

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Message-ID: <36161238.SskTX730U1@avalon>
Date:   Tue, 13 Dec 2016 17:17:40 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Daniel Vetter <daniel@...ll.ch>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        linux-fbdev@...r.kernel.org,
        Teddy Wang <teddy.wang@...iconmotion.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Arnaud Patard <arnaud.patard@...-net.org>
Subject: Re: [RFC PATCH 0/3] staging: remove fbdev drivers

Hi Daniel,

On Thursday 08 Dec 2016 11:10:05 Daniel Vetter wrote:
> On Thu, Dec 08, 2016 at 12:01:19PM +1100, Benjamin Herrenschmidt wrote:
> > On Wed, 2016-11-23 at 10:03 +0200, Tomi Valkeinen wrote:
> > > Hi,
> > > 
> > > Since the fbdev framework is in maintenance mode and all new display
> > > drivers should be made with the DRM framework, remove the fbdev drivers
> > > from staging.
> > > 
> > > Note: the patches are created with git format-patch -D, so they can't be
> > > applied. Only for review.
> > 
> > I missed the discussion where this decision was made, I admit I am
> > unimpressed by it.
> > 
> > DRM drivers don't strike me as suitable for small/slow cores with dumb
> > framebuffers or simple 2D only accel, such as the one found in the ASpeed
> > BMCs.
> 
> We have a helper for simple drivers now, if you take into account the
> massive helper libraries for everything that comes along with drm I expect
> if even dumb panels behind slow spi buses drm is now the more suitable
> subsytem.
> 
> > With drmfb you basically have to shadow everything into memory & copy
> > over everything, and locks you out of simple 2D accel. For a simple text
> > console the result is orders of magnitude slower and memory hungry than
> > a simple fbdev.
> 
> Not true, we have full fbdev emulation, and drivers can implement the 2d
> accel in there. And a bunch of them do. It's just that most teams decided
> that this is pointless waste of their time.j

And I'd argue that a better use of time would be to implement an accelerated 
console that does not use fbdev at all.

> > At least that was the case last I looked at the DRM stuff with Dave,
> > maybe things have changed...
> > 
> > Not everything has a powerful 3D GPU.
> 
> That's correct, and drm can cope. And compared to fbdev there's a very
> active community who improves&refactors it every kernel release to make it
> even better. Since about 2 years (when atomic landed) we merge new drivers
> at a rate of 2-3 per kernel release, and those new drivers get ever simpler
> and smaller thanks to all this work.

-- 
Regards,

Laurent Pinchart