On Mon, Dec 17, 2012 at 10:21 PM, Rob Clark [off-list ref] wrote:

On Mon, Dec 17, 2012 at 11:04 PM, Dave Airlie [off-list ref] wrote:

quoted

quoted

Many developers showed interest in the first RFC, and I've had the opportunity
to discuss it with most of them. I would like to thank (in no particular
order) Tomi Valkeinen for all the time he spend helping me to draft v2, Marcus
Lorentzon for his useful input during Linaro Connect Q4 2012, and Linaro for
inviting me to Connect and providing a venue to discuss this topic.

So this might be a bit off topic but this whole CDF triggered me
looking at stuff I generally avoid:

The biggest problem I'm having currently with the whole ARM graphics
and output world is the proliferation of platform drivers for every
little thing. The whole ordering of operations with respect to things
like suspend/resume or dynamic power management is going to be a real
nightmare if there are dependencies between the drivers. How do you
enforce ordering of s/r operations between all the various components?

I tend to think that sub-devices are useful just to have a way to
probe hw which may or may not be there, since on ARM we often don't
have any alternative..

You can probe the device tree from a normal DRM driver. For example in
nouveau for PPC we probe the OF device tree looking for connectors. I
don't see how sub-devices or extra platform drivers help with that, as
long as the device tree is populated upfront somehow...

Stéphane

but beyond that, suspend/resume, and other
life-cycle aspects, they should really be treated as all one device.
Especially to avoid undefined suspend/resume ordering.

CDF or some sort of mechanism to share panel drivers between drivers
is useful.  Keeping it within drm, is probably a good idea, if nothing
else to simplify re-use of helper fxns (like avi-infoframe stuff, for
example) and avoid dealing with merging changes across multiple trees.
  Treating them more like shared libraries and less like sub-devices
which can be dynamically loaded/unloaded (ie. they should be not built
as separate modules or suspend/resumed or probed/removed independently
of the master driver) is a really good idea to avoid uncovering nasty
synchronization issues later (remove vs modeset or pageflip) or
surprising userspace in bad ways.

quoted

The other thing I'd like you guys to do is kill the idea of fbdev and
v4l drivers that are "shared" with the drm codebase, really just
implement fbdev and v4l on top of the drm layer, some people might
think this is some sort of maintainer thing, but really nothing else
makes sense, and having these shared display frameworks just to avoid
having using drm/kms drivers seems totally pointless. Fix the drm
fbdev emulation if an fbdev interface is needed. But creating a fourth
framework because our previous 3 frameworks didn't work out doesn't
seem like a situation I want to get behind too much.

yeah, let's not have multiple frameworks to do the same thing.. For
fbdev, it is pretty clear that it is a dead end.  For v4l2
(subdev+mcf), it is perhaps bit more flexible when it comes to random
arbitrary hw pipelines than kms.  But to take advantage of that, your
userspace isn't going to be portable anyways, so you might as well use
driver specific properties/ioctls.  But I tend to think that is more
useful for cameras.  And from userspace perspective, kms planes are
less painful to use for output than v4l2, so lets stick to drm/kms for
output (and not try to add camera/capture support to kms).. k, thx

BR,
-R

quoted

Dave.
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