[RFC 0/9] nuclear pageflip

[Ville Syrjälä]

On Wed, Sep 12, 2012 at 07:30:18AM -0500, Rob Clark wrote:
> On Wed, Sep 12, 2012 at 3:59 AM, Ville Syrjälä
> <ville.syrjala at linux.intel.com> wrote:
> > On Tue, Sep 11, 2012 at 05:07:49PM -0500, Rob Clark wrote:
> >> On Tue, Sep 11, 2012 at 4:15 PM, Ben Widawsky <ben at bwidawsk.net> wrote:
> >> > On Sun, 9 Sep 2012 22:19:59 -0500
> >> > Rob Clark <rob at ti.com> wrote:
> >> >
> >> >> On Sun, Sep 9, 2012 at 10:03 PM, Rob Clark <rob.clark at linaro.org> wrote:
> >> >> > From: Rob Clark <rob at ti.com>
> >> >> >
> >> >> > This is following a bit the approach that Ville is taking for atomic-
> >> >> > modeset, in that it is switching over to using properties for everything.
> >> >> > The advantage of this approach is that it makes it easier to add new
> >> >> > attributes to set as part of a page-flip (and even opens the option to
> >> >> > add new object types).
> >> >>
> >> >> oh, and for those wondering what the hell this is all about,
> >> >> nuclear-pageflip is a pageflip that atomically updates the CRTC layer
> >> >> and zero or more attached plane layers, optionally changing various
> >> >> properties such as z-order (or even blending modes, etc) atomically.
> >> >> It includes the option for a test step so userspace compositor can
> >> >> test a proposed configuration (if any properties not marked as
> >> >> 'dynamic' are updated).  This intended to allow, for example, weston
> >> >> compositor to synchronize updates to plane (sprite) layers with CRTC
> >> >> layer.
> >> >>
> >> >
> >> > Can we please name this something different? I complained about this in
> >> > IRC, but I don't know if you hang around in #intel-gfx.
> >> >
> >> > Some suggestions:
> >> > multiplane pageflip
> >> > muliplane atomic pageflip
> >> > atomic multiplane pageflip
> >> > atomic multiflip
> >> > pageflip of atomic and multiplane nature
> >> >
> >> > Nuclear is not at all descriptive and requires as your response shows
> >> > :-)
> >> >
> >>
> >> fair enough.. I was originally calling it atomic-pageflip until
> >> someone (I don't remember who) started calling it nuclear-pageflip to
> >> differentiate from atomic-modeset.  But IMO we could just call the two
> >> ioclts atomic-modeset and atomic-pageflip.  (Or even modeset2 and
> >> pageflip2, but that seems much more boring)
> >
> > My plan has been to use the same ioctl for both uses. They'll need
> > nearly identical handling anyway on the ioctl level. I have something
> > semi-working currently, but I need to clean it up a bit before I can
> > show it to anyone.
> 
> I do think the atomic-pageflip ioctl really should take the crtc-id..
> so probably should be two ioctls, but nearly identical

But then you can't support atomic pageflips across multiple crtcs even
if the hardware would allow it. I would hate to add such limitation to
the API. I can immediately think of a use case; combining several
smaller displays to form a single larger display.

With a unified API you could just add some kind of flag that tells the
kernel that user space really wants an atomic update, and if the
driver/hardware can't do it, it can return an error.

-- 
Ville Syrjälä
Intel OTC