From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= Date: Fri, 28 May 2010 20:06:04 +0000 Subject: Re: Idea of a v4l -> fb interface driver Message-Id: <20100528200604.GA10135@sci.fi> List-Id: References: <4C001643.2070802@gmx.de> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable To: Alex Deucher Cc: Florian Tobias Schandinat , Guennadi Liakhovetski , Jaya Kumar , linux-fbdev@vger.kernel.org, Linux Media Mailing List On Fri, May 28, 2010 at 03:41:46PM -0400, Alex Deucher wrote: > On Fri, May 28, 2010 at 3:15 PM, Florian Tobias Schandinat > > If he wants different (independent) content on each output, just provide > > multiple /dev/fbX devices. I admit that we could use a controlling inte= rface > > here that decides which user (application) might draw at a time to the > > interface which they currently only do if they are the active VT. > > If you want 2 or more outputs to be merged as one just configure this i= n the > > driver. > > The only thing that is impossible to do in fbdev is controlling 2 or mo= re > > independent display outputs that access the same buffer. But that's not= an > > issue I think. > > The things above only could use a unification of how to set them up on > > module load time (as only limited runtime changes are permited given th= at we > > must always be able to support a mode that we once entered during runti= me). > > >=20 > What about changing outputs on the fly (turn off VGA, turn on DVI, > switch between multi-head and single-head, etc) or encoders shared > between multiple connectors (think a single dac shared between a VGA > and a TV port); how do you expose them easily as separate fbdevs? > Lots of stuff is doable with fbdev, but it's nicer with kms. But actually getting your data onto the screen is a lot easier with fbdev. There's no standard API in drm to actually allocate the framebuffer and manipulate it. You always need a user space driver to go along with the kernel bits. I'm not saying fbdev is better than drm/kms but at least it can be used to write simple applications that work across different hardware. Perhaps that's something that should be addressed in the drm API. --=20 Ville Syrj=E4l=E4 syrjala@sci.fi http://www.sci.fi/~syrjala/