[RFC 0/9] nuclear pageflip

[Rob Clark]

On Sat, Sep 15, 2012 at 12:04 PM, Ville Syrjälä <syrjala at sci.fi> wrote:
> On Sat, Sep 15, 2012 at 11:07:02AM -0500, Rob Clark wrote:
>> On Sat, Sep 15, 2012 at 9:56 AM, Ville Syrjälä <syrjala at sci.fi> wrote:
>> > On Fri, Sep 14, 2012 at 09:12:35PM -0500, Rob Clark wrote:
>> >> On Thu, Sep 13, 2012 at 11:35 AM, Rob Clark <rob.clark at linaro.org> wrote:
>> >> > note that the test phase doesn't need vblank events, and also
>> >> > shouldn't -EBUSY if there is still a pending flip[*], so I'd propose
>> >> > that however we go about pageflip (one super-ioctl, or one per crtc),
>> >> > we could use the atomic-modeset ioctl for the test step
>> >>
>> >> actually, I think I take this back..  one thing that was discussed on
>> >> IRC, but didn't make it to this email thread is the behavior of
>> >> non-specified properties.  What I am thinking:
>> >>
>> >> modeset: unspecified properties revert to default
>> >> pageflip: unspecified properties preserve current value
>> >
>> > Why on earth would you want to revert stuff to default? That's only
>> > going to make the code more complex.
>>
>> well, you need to do it *somewhere*..  possibly it can be on drm file
>> close or dropmaster.  But modeset seems like a sensible place.  I
>> really hate the v4l2 approach of preserving settings for the next
>> process that opens the device.
>
> Ah so it's the same workaround for lack of proper state management.
> Each master should just have its own state. Or if that's too much to
> ask, at least the reset could be done only when the master changes.
>
> If you do it at modeset time, which props do you reset anyway? All of
> them for the whole device? Just the ones related to the CRTCs undergoing
> the modeset? What if there's some conflict between the default values
> on that CRTC and the current values on another CRTC? What about properties
> for planes that can move across CRTCs? This kind of partial state reset
> opens up a lot of open questions, so a full reset at master switch seems
> a lot more sensible.

Well, if you reset *all* properties on modeset, then crtcs's that
aren't set in the modeset go off..  atomic-modeset is userspace saying
"here is the entire config I want.. go make it happen".  But I guess
it does get a bit easier to implement legacy setcrtc on top of the new
mechanism if untouched properties preserve their value.

I could live w/ just reset on master change.. that meets my minimum
requirement of not carrying state between different processes using
the device.  Having a flag indicating 'reset untouched properties'
would be useful if the default behavior is to preserve.

I still think setcrtc and pageflip shouldn't be mashed into a single ioctl :-)

BR,
-R

> --
> Ville Syrjälä
> syrjala at sci.fi
> http://www.sci.fi/~syrjala/
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