On Wed, 12 May 2021 09:50:14 -0300 Leandro Ribeiro <leandro.ribeiro@xxxxxxxxxxxxx> wrote: > On 5/6/21 5:50 AM, Pekka Paalanen wrote: > > On Wed, 28 Apr 2021 18:36:50 -0300 > > Leandro Ribeiro <leandro.ribeiro@xxxxxxxxxxxxx> wrote: > > > >> In this patch we add a section to document what userspace should do to > >> find out the CRTC index. This is important as there are multiple places > >> in the documentation that need this, so it's better to just point to > >> this section and avoid repetition. > >> > >> Signed-off-by: Leandro Ribeiro <leandro.ribeiro@xxxxxxxxxxxxx> > >> --- > >> Documentation/gpu/drm-uapi.rst | 14 ++++++++++++++ > >> drivers/gpu/drm/drm_debugfs_crc.c | 9 +++++---- > >> include/uapi/drm/drm.h | 3 ++- > >> 3 files changed, 21 insertions(+), 5 deletions(-) > >> > >> diff --git a/Documentation/gpu/drm-uapi.rst b/Documentation/gpu/drm-uapi.rst > >> index 04bdc7a91d53..1aa52a6ac567 100644 > >> --- a/Documentation/gpu/drm-uapi.rst > >> +++ b/Documentation/gpu/drm-uapi.rst > >> @@ -457,6 +457,20 @@ Userspace API Structures > >> .. kernel-doc:: include/uapi/drm/drm_mode.h > >> :doc: overview > >> > >> +.. _crtc_index: > >> + > >> +CRTC index > >> +---------- > >> + > >> +In some situations, it is important for userspace to find out the index of a > > > > That could be said about everything, so this sentence has no > > information value. Instead, you could start by stating that CRTCs have > > both an object ID and an index, and they are not the same thing. CRTC > > index is used in cases where a densely packed identifier for a CRTC is > > needed, e.g. in bit-for-crtc masks, where using the object ID would not > > work. > > > >> +CRTC. The CRTC index should not be confused with its object id. > >> + > >> +In order to do this, userspace should first query the resources object > > > > Instead of saying what userspace must do, you could just explain where > > it can be observed. > > > >> +from the device that owns the CRTC (using the DRM_IOCTL_MODE_GETRESOURCES > > > > So here you might start with: DRM_IOCTL_MODE_GETRESOURCES populates a > > structure with an array of CRTC IDs. CRTC's index is its index in that > > array. > > > >> +ioctl). The resources object contains a pointer to an array of CRTC's, and also > >> +the number of entries of the array. The index of the CRTC is the same as its > >> +position in this array. > > > > Anyway, the idea here is right. > > > > So what about: > > CRTC's have both an object ID and an index, and they should not be > confused. The index is used in cases where a densely packed identifier > for a CRTC is needed, for instance in a bitmask of CRTC's. (maybe a link > to the possible_crtcs field of struct drm_mode_get_plane? as example) > > DRM_IOCTL_MODE_GETRESOURCES populates a structure with an array of CRTC > id's, and the CRTC index is its position in this array. Sure, sounds good. Capitalized 'ID'? Thanks, pq
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