On Fri, 7 Aug 2020 11:07:06 +0200 Daniel Vetter <daniel@xxxxxxxx> wrote: > On Thu, Aug 06, 2020 at 10:33:31AM +0000, Simon Ser wrote: > > Some drivers may expose primary planes compatible with multiple CRTCs. > > Make this clear in the docs: the current wording may be misunderstood as > > "exactly one primary plane per CRTC". > > > > Signed-off-by: Simon Ser <contact@xxxxxxxxxxx> > > Cc: Daniel Vetter <daniel@xxxxxxxx> > > --- > > drivers/gpu/drm/drm_plane.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c > > index b7b90b3a2e38..108a922e8c23 100644 > > --- a/drivers/gpu/drm/drm_plane.c > > +++ b/drivers/gpu/drm/drm_plane.c > > @@ -49,8 +49,8 @@ > > * &struct drm_plane (possibly as part of a larger structure) and registers it > > * with a call to drm_universal_plane_init(). > > * > > - * Cursor and overlay planes are optional. All drivers should provide one > > - * primary plane per CRTC to avoid surprising userspace too much. See enum > > + * Cursor and overlay planes are optional. All drivers should provide at least > > + * one primary plane per CRTC to avoid surprising userspace too much. See enum > > I think that's even more confusing, since this reads like there could be > multiple primary planes for a specific CRTC. That's not the case, there' > only one pointer going from drm_crtc->primary to a drm_plane in the > kernel. There could be multiple primary planes *usable* for a specific CRTC but just one used at a time, right? > The problem is that userspace doesn't have a drm_property to read this > pointer, and needs to guess. > > I thought the rule is: > > Nth primary plane (or cursor) is the primary plane for the Nth crtc. > Enumaration with increasing drm kms object ids. Why is that needed? With universal planes, I thought drmModePlane::possible_crtcs bitmask is trustworthy? In the legacy KMS UAPI you can't even pick your primary plane, because it's implied in drmModeSetCrtc(), right? > And I guess we should explain that on some hw any plane (including primary > ones, since that's only a sw construct) can be freely assinged to crtc. > > Yes it's probably the most gloriously bonkers uapi we've come up with. > Might be so bad that a libdrm helper to look up the primary plane for a > crtc (or it's cursor plane if it exists) would be in order :-) I'm not sure I see the bonkers there. Thanks, pq > > Cheers, Daniel > > > > * drm_plane_type for a more in-depth discussion of these special uapi-relevant > > * plane types. Special planes are associated with their CRTC by calling > > * drm_crtc_init_with_planes(). > > -- > > 2.28.0 > > > > >
Attachment:
pgpn24pll2ZgF.pgp
Description: OpenPGP digital signature
_______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
