[PATCH libdrm v2] Header: Add rotation property fields

[Daniel Vetter]

On Mon, Apr 24, 2017 at 01:51:39PM +0100, Emil Velikov wrote:
> On 18 April 2017 at 23:16, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> > On Tue, Apr 18, 2017 at 8:33 PM, Kristian Høgsberg <hoegsberg at gmail.com> wrote:
> >>>> As far as I understand the property mechanism, the numeric values
> >>>> aren't actually ABI. The string names of the enum values are the ABI
> >>>> and you're supposed to parse the enum info and discover the numerical
> >>>> values. For example:
> >>>> https://git.collabora.com/cgit/user/daniels/weston.git/tree/libweston/compositor-drm.c?h=wip/2017-03/atomic-v10-WIP#n570
> >>>>
> >>> Note sure I agree, yet then again my kernel experience is less than yours.
> >>> Do check the following commit and feel free to search the ML thread
> >>> that inspired it.
> >>
> >> I haven't worked much with the property mechanism tbh, but I know
> >> Daniel (Stone) jumped through all those hoops to avoid hard-coding the
> >> enum values.
> >
> > In theory, this is correct and is how it's supposed to be done. In
> > practice, for a bunch of properties at least, we deal with the reality
> > of userspace being lazy and assuming that the enum values match with
> > the encode they send over the wire and tears result if we ever chance
> > that. I still think that going through the strings should be the
> > better way, since it makes it much easier to add/remove certain enum
> > values, depending upon what the hw/driverr combo can pull off.
> >
> > The story is different for the properties themselves, there you
> > definitely need to make the name->prop id lookup, and you also need to
> > do that mapping for each object separately (because the value range is
> > attached to the prop, for uabi reasons, but might need to be
> > per-object).
> 
> Daniel, this that mean that we're OK with moving DRM_ROTATE* [+others]
> to a ABI header?

With a big comment, but yeah this is special.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch