On Fri, 03 Oct 2014 09:56:27 +0200
, Hans de Goede [off-list ref]
 wrote:

On 10/03/2014 01:31 AM, Julian Calaby wrote:

quoted

On Fri, Oct 3, 2014 at 1:14 AM, jonsmirl at gmail.com [off-list ref] wrote:

quoted

Because you are creating two different device tree nodes describing a
single piece of hardware and that's not suppose to happen in a device
tree.  The accurate description of the hardware is being perverted to
solve a software problem.

One node describes the hardware in a format to make simplefb happy.
Another node describes the same hardware in a format to make the
device specific driver happy.

Stupid question: What about mangling an existing device node to be
simplefb compatible, and writing simplefb to be binding agnostic?

That will not work, with simplefb a single node represents the currently
active video output. While in real hardware that may involve multiple
blocks, e.g on sunxi for hdmi out this involves the compositor (which
generates video data from 1 or more layers) which feeds into the
lcd-controller (which in this case is only used to generate hsync + vsync)
signals really, which feeds into the hdmi encoder, all 3 of which are
separate hardware blocks with their own clocks, etc.

The answer here should be, 'whoever does the DMA'.

Julian's suggestion is actually the sanest approach, and there is
precedence for doing exactly that in DT, both for serial devices
(of_serial.c) and framebuffers (offb.c).

g.