Hi Rob, On Thursday 18 December 2014 19:55:24 Rob Clark wrote: > On Thu, Dec 18, 2014 at 4:22 PM, Daniel Vetter <daniel@xxxxxxxx> wrote: > >>>>>> TODO move definition of tokens to drm_fourcc.h? > >>>>> > >>>>> Seems orthogonal imo. Another todo is to add checking to all > >>>>> drivers to reject it if it's not 0 with -EINVAL. Otherwise we have yet > >>>>> another case of an ioctl with fields that can't actually be used > >>>>> everywhere. > >>>> > >>>> Could we please add the check in core code instead of drivers ? > >>> > >>> Nope since then no driver could ever use that extension. Defeats the > >>> point ;-) > >> > >> Except if we follow the proposal of adding a flag to tell whether a > >> driver supports the extension ;-) > > > > I'm not a terrible big fan of driver flags, mostly because I've seen too > > much of the horrible stuff in dri1. Imo much better to pass everything to > > drivers and help them out with helpers if needed. I might be going > > overboard a bit with my bias against driver flags ;-) > > I ventured a little ways down the thought path of adding list of > supported modifier tokens per plane.. and then doing more complete > checks in the core. But then the question is, what about cases where > some tiling format is only supported for UV but not Y, etc.. it > quickly gets ugly. >From my experience with V4L2 expressing such constraints in a way that would be both simple and comprehensive isn't possible. We should aim for the common case, and I agree that finding out what the common case is would require implementing the feature first. However, it would be pretty easy to flag whether a driver supports this new API at all. That could be used to zero the extra fields. > I think for now better to let the driver do this (with a must_be_all_zeros() > helper for what I expect will be the common case initially). If common > patterns emerge, then we refactor out a better helper.. -- Regards, Laurent Pinchart _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
