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drm/doc: document DRM_IOCTL_MODE_CREATE_DUMB

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The main motivation is to repeat that dumb buffers should not be
abused for anything else than basic software rendering with KMS.
User-space devs are more likely to look at the IOCTL docs than to
actively search for the driver-oriented "Dumb Buffer Objects"
section.

v2: reference DRM_CAP_DUMB_BUFFER, DRM_CAP_DUMB_PREFERRED_DEPTH and
DRM_CAP_DUMB_PREFER_SHADOW (Pekka)

Signed-off-by: Simon Ser <contact@emersion.fr>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230821131548.269204-1-contact@emersion.fr
This commit is contained in:
Simon Ser
2023-08-21 13:15:56 +00:00
parent d4b3842285
commit b8644c4ae2
3 changed files with 36 additions and 2 deletions
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include/uapi/drm/drm.h
+20
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@@ -1134,6 +1134,26 @@ extern "C" {
#define DRM_IOCTL_MODE_PAGE_FLIP DRM_IOWR(0xB0, struct drm_mode_crtc_page_flip)
#define DRM_IOCTL_MODE_DIRTYFB DRM_IOWR(0xB1, struct drm_mode_fb_dirty_cmd)
/**
* DRM_IOCTL_MODE_CREATE_DUMB - Create a new dumb buffer object.
*
* KMS dumb buffers provide a very primitive way to allocate a buffer object
* suitable for scanout and map it for software rendering. KMS dumb buffers are
* not suitable for hardware-accelerated rendering nor video decoding. KMS dumb
* buffers are not suitable to be displayed on any other device than the KMS
* device where they were allocated from. Also see
* :ref:`kms_dumb_buffer_objects`.
*
* The IOCTL argument is a struct drm_mode_create_dumb.
*
* User-space is expected to create a KMS dumb buffer via this IOCTL, then add
* it as a KMS framebuffer via &DRM_IOCTL_MODE_ADDFB and map it via
* &DRM_IOCTL_MODE_MAP_DUMB.
*
* &DRM_CAP_DUMB_BUFFER indicates whether this IOCTL is supported.
* &DRM_CAP_DUMB_PREFERRED_DEPTH and &DRM_CAP_DUMB_PREFER_SHADOW indicate
* driver preferences for dumb buffers.
*/
#define DRM_IOCTL_MODE_CREATE_DUMB DRM_IOWR(0xB2, struct drm_mode_create_dumb)
#define DRM_IOCTL_MODE_MAP_DUMB DRM_IOWR(0xB3, struct drm_mode_map_dumb)
#define DRM_IOCTL_MODE_DESTROY_DUMB DRM_IOWR(0xB4, struct drm_mode_destroy_dumb)