On Friday, March 5th, 2021 at 9:28 AM, Pekka Paalanen ppaalanen@gmail.com wrote:
+/**
- DRM_CAP_DUMB_PREFERRED_DEPTH
- The preferred depth (in bits) for dumb buffers.
this is literally depth, not bits per pixel, right?
"Depth" is pretty ambiguous [1]. Maybe we should be more explicit here and say that it's the number of bits used to indicate the color of a single pixel? And maybe add a note that it's different from bits per pixel?
[1]: https://en.wikipedia.org/wiki/Color_depth
- */
#define DRM_CAP_DUMB_PREFERRED_DEPTH 0x3 +/**
- DRM_CAP_DUMB_PREFER_SHADOW
- If set to 1, the driver prefers userspace to render to a shadow buffer
- instead of directly rendering to a dumb buffer.
Maybe add something like:
For best speed, userspace should do streaming ordered memory copies into the dumb buffer and never read from it.
Isn't that correct?
Good call, will add.
- */
#define DRM_CAP_DUMB_PREFER_SHADOW 0x4 +/**
- DRM_CAP_PRIME
- Bitfield of supported PRIME sharing capabilities. See &DRM_PRIME_CAP_IMPORT
- and &DRM_PRIME_CAP_EXPORT.
- */
#define DRM_CAP_PRIME 0x5 +/**
- DRM_PRIME_CAP_IMPORT
- If this bit is set in &DRM_CAP_PRIME, the driver supports importing PRIME
- buffers.
What are PRIME buffers?
Will add something like:
PRIME buffers are exposed as dma-buf file descriptors. See Documentation/gpu/drm-mm.rst, section "PRIME Buffer Sharing".
- */
#define DRM_PRIME_CAP_IMPORT 0x1 +/**
- DRM_PRIME_CAP_EXPORT
- If this bit is set in &DRM_CAP_PRIME, the driver supports exporting PRIME
- buffers.
What's the export API? HandleToFD()?
Yes. Will add a note about it. Same for import.
- */
#define DRM_PRIME_CAP_EXPORT 0x2 +/**
- DRM_CAP_TIMESTAMP_MONOTONIC
- If set to 0, the kernel will report timestamps with the realtime clock in
- struct drm_event_vblank. If set to 1, the kernel will report timestamps with
- the monotonic clock.
I think it would be more explicit to say CLOCK_REALTIME and CLOCK_MONOTONIC, because there are things like CLOCK_MONOTONIC_RAW which is different. Mention clock_gettime()?
Ack, better be explicit here.
- */
#define DRM_CAP_TIMESTAMP_MONOTONIC 0x6 +/**
- DRM_CAP_ASYNC_PAGE_FLIP
- If set to 1, the driver supports &DRM_MODE_PAGE_FLIP_ASYNC.
Does this apply equally to both legacy and atomic KMS API?
Yes (it's included in DRM_MODE_ATOMIC_FLAGS), but I heard that some drivers get it wrong.
- */
#define DRM_CAP_ASYNC_PAGE_FLIP 0x7 -/*
- The CURSOR_WIDTH and CURSOR_HEIGHT capabilities return a valid widthxheight
- combination for the hardware cursor. The intention is that a hardware
- agnostic userspace can query a cursor plane size to use.
+/**
- DRM_CAP_CURSOR_WIDTH
- The ``CURSOR_WIDTH`` and ``CURSOR_HEIGHT`` capabilities return a valid
- width x height combination for the hardware cursor. The intention is that a
*/
- hardware agnostic userspace can query a cursor plane size to use.
- Note that the cross-driver contract is to merely return a valid size;
- drivers are free to attach another meaning on top, eg. i915 returns the
- maximum plane size.
#define DRM_CAP_CURSOR_WIDTH 0x8 +/**
- DRM_CAP_CURSOR_HEIGHT
- See &DRM_CAP_CURSOR_WIDTH.
- */
#define DRM_CAP_CURSOR_HEIGHT 0x9 +/**
- DRM_CAP_ADDFB2_MODIFIERS
- If set to 1, the driver supports supplying modifiers in the
- &DRM_IOCTL_MODE_ADDFB2 ioctl.
- */
#define DRM_CAP_ADDFB2_MODIFIERS 0x10 +/**
- DRM_CAP_PAGE_FLIP_TARGET
- If set to 1, the driver supports the &DRM_MODE_PAGE_FLIP_TARGET_ABSOLUTE and
- &DRM_MODE_PAGE_FLIP_TARGET_RELATIVE flags in
- &drm_mode_crtc_page_flip_target.flags for the &DRM_IOCTL_MODE_PAGE_FLIP
- ioctl.
- */
#define DRM_CAP_PAGE_FLIP_TARGET 0x11 +/**
- DRM_CAP_CRTC_IN_VBLANK_EVENT
- If set to 1, the kernel supports reporting the CRTC ID in
- &drm_event_vblank.crtc_id.
Does this not apply also to the pageflip / atomic completion event?
Both DRM_EVENT_VBLANK and DRM_EVENT_FLIP_COMPLETE use the struct drm_event_vblank, so yes. I'll mention these two events explicitly.
- */
#define DRM_CAP_CRTC_IN_VBLANK_EVENT 0x12 +/**
- DRM_CAP_SYNCOBJ
- If set to 1, the driver supports sync objects. See
- Documentation/gpu/drm-mm.rst, section "DRM Sync Objects".
- */
#define DRM_CAP_SYNCOBJ 0x13 +/**
- DRM_CAP_SYNCOBJ_TIMELINE
- If set to 1, the driver supports timeline operations on sync objects. See
- Documentation/gpu/drm-mm.rst, section "DRM Sync Objects".
- */
#define DRM_CAP_SYNCOBJ_TIMELINE 0x14
/* DRM_IOCTL_GET_CAP ioctl argument type */
I'm so happy seeing this doc appear! :-) Sorry for trolling you into it. ;-)
Np :)