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drm: introduce CLOSEFB IOCTL

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This new IOCTL allows callers to close a framebuffer without
disabling planes or CRTCs. This takes inspiration from Rob Clark's
unref_fb IOCTL [1] and DRM_MODE_FB_PERSIST [2].

User-space patch for wlroots available at [3]. IGT test available
at [4].

v2: add an extra pad field just in case we want to extend this IOCTL
in the future (Pekka, Sima).

[1]: https://lore.kernel.org/dri-devel/20170509153654.23464-1-robdclark@gmail.com/
[2]: https://lore.kernel.org/dri-devel/20211006151921.312714-1-contact@emersion.fr/
[3]: https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/4394
[4]: https://lists.freedesktop.org/archives/igt-dev/2023-October/063294.html

Signed-off-by: Simon Ser <contact@emersion.fr>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Cc: Dennis Filder <d.filder@web.de>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Rob Clark <robdclark@gmail.com>
Cc: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20231020101926.145327-2-contact@emersion.fr
This commit is contained in:
Simon Ser 2023-10-20 10:19:45 +00:00
parent 0226ba393e
commit d208d87566
5 changed files with 55 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
drivers/gpu/drm/drm_crtc_internal.h
View file

@ -222,6 +222,8 @@ int drm_mode_addfb2_ioctl(struct drm_device *dev,
void *data, struct drm_file *file_priv);
int drm_mode_rmfb_ioctl(struct drm_device *dev,
void *data, struct drm_file *file_priv);
int drm_mode_closefb_ioctl(struct drm_device *dev,
void *data, struct drm_file *file_priv);
int drm_mode_getfb(struct drm_device *dev,
void *data, struct drm_file *file_priv);
int drm_mode_getfb2_ioctl(struct drm_device *dev,

22
drivers/gpu/drm/drm_framebuffer.c
View file

@ -480,6 +480,28 @@ int drm_mode_rmfb_ioctl(struct drm_device *dev,
return drm_mode_rmfb(dev, *fb_id, file_priv);
}
int drm_mode_closefb_ioctl(struct drm_device *dev,
void *data, struct drm_file *file_priv)
{
struct drm_mode_closefb *r = data;
struct drm_framebuffer *fb;
int ret;
if (!drm_core_check_feature(dev, DRIVER_MODESET))
return -EOPNOTSUPP;
if (r->pad)
return -EINVAL;
fb = drm_framebuffer_lookup(dev, file_priv, r->fb_id);
if (!fb)
return -ENOENT;
ret = drm_mode_closefb(fb, file_priv);
drm_framebuffer_put(fb);
return ret;
}
/**
* drm_mode_getfb - get FB info
* @dev: drm device for the ioctl

1
drivers/gpu/drm/drm_ioctl.c
View file

@ -675,6 +675,7 @@ static const struct drm_ioctl_desc drm_ioctls[] = {
DRM_IOCTL_DEF(DRM_IOCTL_MODE_ADDFB, drm_mode_addfb_ioctl, 0),
DRM_IOCTL_DEF(DRM_IOCTL_MODE_ADDFB2, drm_mode_addfb2_ioctl, 0),
DRM_IOCTL_DEF(DRM_IOCTL_MODE_RMFB, drm_mode_rmfb_ioctl, 0),
DRM_IOCTL_DEF(DRM_IOCTL_MODE_CLOSEFB, drm_mode_closefb_ioctl, 0),
DRM_IOCTL_DEF(DRM_IOCTL_MODE_PAGE_FLIP, drm_mode_page_flip_ioctl, DRM_MASTER),
DRM_IOCTL_DEF(DRM_IOCTL_MODE_DIRTYFB, drm_mode_dirtyfb_ioctl, DRM_MASTER),
DRM_IOCTL_DEF(DRM_IOCTL_MODE_CREATE_DUMB, drm_mode_create_dumb_ioctl, 0),

20
include/uapi/drm/drm.h
View file

@ -1218,6 +1218,26 @@ extern "C" {
#define DRM_IOCTL_SYNCOBJ_EVENTFD DRM_IOWR(0xCF, struct drm_syncobj_eventfd)
/**
* DRM_IOCTL_MODE_CLOSEFB - Close a framebuffer.
*
* This closes a framebuffer previously added via ADDFB/ADDFB2. The IOCTL
* argument is a framebuffer object ID.
*
* This IOCTL is similar to &DRM_IOCTL_MODE_RMFB, except it doesn't disable
* planes and CRTCs. As long as the framebuffer is used by a plane, it's kept
* alive. When the plane no longer uses the framebuffer (because the
* framebuffer is replaced with another one, or the plane is disabled), the
* framebuffer is cleaned up.
*
* This is useful to implement flicker-free transitions between two processes.
*
* Depending on the threat model, user-space may want to ensure that the
* framebuffer doesn't expose any sensitive user information: closed
* framebuffers attached to a plane can be read back by the next DRM master.
*/
#define DRM_IOCTL_MODE_CLOSEFB DRM_IOWR(0xD0, struct drm_mode_closefb)
/*
* Device specific ioctls should only be in their respective headers
* The device specific ioctl range is from 0x40 to 0x9f.

10
include/uapi/drm/drm_mode.h
View file

@ -1323,6 +1323,16 @@ struct drm_mode_rect {
__s32 y2;
};
/**
* struct drm_mode_closefb
* @fb_id: Framebuffer ID.
* @pad: Must be zero.
*/
struct drm_mode_closefb {
__u32 fb_id;
__u32 pad;
};
#if defined(__cplusplus)
}
#endif