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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20161208101005.6ufl3d4qvwprosju@phenom.ffwll.local>
Date:   Thu, 8 Dec 2016 11:10:05 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:     Tomi Valkeinen <tomi.valkeinen@...com>,
        linux-fbdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        Noralf Trønnes <noralf@...nnes.org>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Teddy Wang <teddy.wang@...iconmotion.com>,
        Arnaud Patard <arnaud.patard@...-net.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/3] staging: remove fbdev drivers

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

> 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.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch