On 5/12/21 10:04 AM, Pekka Paalanen wrote:
On Wed, 12 May 2021 09:50:14 -0300 Leandro Ribeiro leandro.ribeiro@collabora.com wrote:
On 5/6/21 5:50 AM, Pekka Paalanen wrote:
On Wed, 28 Apr 2021 18:36:50 -0300 Leandro Ribeiro leandro.ribeiro@collabora.com 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@collabora.com
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'?
Sure, I'll add this change.
Thanks, Leandro