linux-kernel - Re: No more new fbdev drivers, please

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Date:	Tue, 29 Sep 2015 11:33:27 +0300
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Gerd Hoffmann <kraxel@...hat.com>
Cc:	Daniel Vetter <daniel@...ll.ch>,
	David Herrmann <dh.herrmann@...il.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	linux-fbdev <linux-fbdev@...r.kernel.org>,
	Teddy Wang <teddy.wang@...iconmotion.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	DRI Development <dri-devel@...ts.freedesktop.org>,
	Arnaud Patard <apatard@...driva.com>,
	Tomi Valkeinen <tomi.valkeinen@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Dave Airlie <airlied@...hat.com>,
	Sudip Mukherjee <sudipm.mukherjee@...il.com>
Subject: Re: No more new fbdev drivers, please

Hi Gerd,

On Tuesday 29 September 2015 10:23:23 Gerd Hoffmann wrote:
> On Mo, 2015-09-28 at 14:36 +0200, Daniel Vetter wrote:
> > On Mon, Sep 28, 2015 at 09:39:13AM +0200, Gerd Hoffmann wrote:
> > >   Hi,
> > >   
> > > > As Daniel mentioned, the connector+encoder+crtc combination is one of
> > > > those simplifications that would make sense if more such drivers are
> > > > added.
> > > 
> > > Another one is memory management.  It's pretty complex because it can
> > > handle _way_ more than what simple drivers need, and the result is
> > > _alot_ of ttm boilerplate in the drivers.
> > 
> > ttm is pretty impressive overkill for most simplistic drm drivers. If you
> > just need contiguous framebuffers for display then the cma helpers should
> > take care of pretty much all the boilerplate for you. They have ready-made
> > simple gem and dumb framebuffer mmap support, which is all a basic kms
> > driver needs.
> 
> Does that work on !arm meanwhile?  Last time I checked (when writing
> bochsdrm, around v3.14) the cma helpers didn't even build on x86 ...

config DRM_GEM_CMA_HELPER
        bool
        depends on DRM && HAVE_DMA_ATTRS
        help
          Choose this if you need the GEM CMA helper functions

x86 defines HAVE_DMA_ATTRS.

-- 
Regards,

Laurent Pinchart

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