Re: [RFC v2 0/5] Common Display Framework

[Sascha Hauer <s.hauer@pengutronix.de>]

On Thu, Dec 27, 2012 at 10:04:22AM -0600, Rob Clark wrote:
> On Mon, Dec 24, 2012 at 11:27 AM, Laurent Pinchart
> <laurent.pinchart@ideasonboard.com> wrote:
> > On Wednesday 19 December 2012 16:57:56 Jani Nikula wrote:
> >> It just seems to me that, at least from a DRM/KMS perspective, adding
> >> another layer (ÍF) for HDMI or DP (or legacy outputs) would be
> >> overengineering it. They are pretty well standardized, and I don't see there
> >> would be a need to write multiple display drivers for them. Each display
> >> controller has one, and can easily handle any chip specific requirements
> >> right there. It's my gut feeling that an additional framework would just get
> >> in the way. Perhaps there could be more common HDMI/DP helper style code in
> >> DRM to reduce overlap across KMS drivers, but that's another thing.
> >>
> >> So is the HDMI/DP drivers using CDF a more interesting idea from a non-DRM
> >> perspective? Or, put another way, is it more of an alternative to using DRM?
> >> Please enlighten me if there's some real benefit here that I fail to see!
> >
> > As Rob pointed out, you can have external HDMI/DP encoders, and even internal
> > HDMI/DP encoder IPs can be shared between SoCs and SoC vendors. CDF aims at
> > sharing a single driver between SoCs and boards for a given HDMI/DP encoder.
> 
> just fwiw, drm already has something a bit like this.. the i2c
> encoder-slave.  With support for a couple external i2c encoders which
> could in theory be shared between devices.

The problem with this code is that it only works when the i2c device is
registered by a master driver. Once the i2c device comes from the
devicetree there is no possibility to find it.

Sascha

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