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]. [1]: https://lore.kernel.org/dri-devel/20170509153654.23464-1-robdclark@xxxxxxxxx/ [2]: https://lore.kernel.org/dri-devel/20211006151921.312714-1-contact@xxxxxxxxxxx/ [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@xxxxxxxxxxx> Acked-by: Pekka Paalanen <pekka.paalanen@xxxxxxxxxxxxx> Cc: Hans de Goede <hdegoede@xxxxxxxxxx> Cc: Dennis Filder <d.filder@xxxxxx> Cc: Daniel Vetter <daniel@xxxxxxxx> Cc: Rob Clark <robdclark@xxxxxxxxx> Cc: Sean Paul <seanpaul@xxxxxxxxxxxx> --- drivers/gpu/drm/drm_crtc_internal.h | 2 ++ drivers/gpu/drm/drm_framebuffer.c | 19 +++++++++++++++++++ drivers/gpu/drm/drm_ioctl.c | 1 + include/uapi/drm/drm.h | 20 ++++++++++++++++++++ 4 files changed, 42 insertions(+) diff --git a/drivers/gpu/drm/drm_crtc_internal.h b/drivers/gpu/drm/drm_crtc_internal.h index 8556c3b3ff88..6b646e0783be 100644 --- a/drivers/gpu/drm/drm_crtc_internal.h +++ b/drivers/gpu/drm/drm_crtc_internal.h @@ -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, diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c index 62306196808c..78da835c67c6 100644 --- a/drivers/gpu/drm/drm_framebuffer.c +++ b/drivers/gpu/drm/drm_framebuffer.c @@ -482,6 +482,25 @@ 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) +{ + uint32_t *fb_id = data; + struct drm_framebuffer *fb; + int ret; + + if (!drm_core_check_feature(dev, DRIVER_MODESET)) + return -EOPNOTSUPP; + + fb = drm_framebuffer_lookup(dev, file_priv, *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 diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c index 77590b0f38fa..44fda68c28ae 100644 --- a/drivers/gpu/drm/drm_ioctl.c +++ b/drivers/gpu/drm/drm_ioctl.c @@ -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), diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h index 794c1d857677..a9b7dc9da163 100644 --- a/include/uapi/drm/drm.h +++ b/include/uapi/drm/drm.h @@ -1198,6 +1198,26 @@ 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, unsigned int) + /* * Device specific ioctls should only be in their respective headers * The device specific ioctl range is from 0x40 to 0x9f. -- 2.42.0
