This new ADDFB2 flag allows callers to mark a framebuffer as "persistent", and no longer have RMFB semantics when the DRM file is closed.
[1]: https://lore.kernel.org/dri-devel/YTJypepF1Hpc2YYT@reader/ Signed-off-by: Simon Ser <cont...@emersion.fr> Cc: Hans de Goede <hdego...@redhat.com> Cc: Dennis Filder <d.fil...@web.de> Cc: Daniel Vetter <dan...@ffwll.ch> Cc: Pekka Paalanen <ppaala...@gmail.com> --- I'm not sure this is enough, but posting this to get initial feedback and allow to start e.g. Plymouth experiments. I'll follow up with an IGT test soon. drivers/gpu/drm/drm_framebuffer.c | 6 ++++-- include/uapi/drm/drm_mode.h | 15 +++++++++++++++ 2 files changed, 19 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c index 07f5abc875e9..9b398838e1f4 100644 --- a/drivers/gpu/drm/drm_framebuffer.c +++ b/drivers/gpu/drm/drm_framebuffer.c @@ -292,7 +292,8 @@ drm_internal_framebuffer_create(struct drm_device *dev, struct drm_framebuffer *fb; int ret; - if (r->flags & ~(DRM_MODE_FB_INTERLACED | DRM_MODE_FB_MODIFIERS)) { + if (r->flags & ~(DRM_MODE_FB_INTERLACED | DRM_MODE_FB_MODIFIERS | + DRM_MODE_FB_PERSIST)) { DRM_DEBUG_KMS("bad framebuffer flags 0x%08x\n", r->flags); return ERR_PTR(-EINVAL); } @@ -789,7 +790,8 @@ void drm_fb_release(struct drm_file *priv) * at it any more. */ list_for_each_entry_safe(fb, tfb, &priv->fbs, filp_head) { - if (drm_framebuffer_read_refcount(fb) > 1) { + if (drm_framebuffer_read_refcount(fb) > 1 && + !(fb->flags & DRM_MODE_FB_PERSIST)) { list_move_tail(&fb->filp_head, &arg.fbs); } else { list_del_init(&fb->filp_head); diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h index e1e351682872..c7a7089ec31e 100644 --- a/include/uapi/drm/drm_mode.h +++ b/include/uapi/drm/drm_mode.h @@ -662,6 +662,21 @@ struct drm_mode_fb_cmd { #define DRM_MODE_FB_INTERLACED (1<<0) /* for interlaced framebuffers */ #define DRM_MODE_FB_MODIFIERS (1<<1) /* enables ->modifer[] */ +/** + * DRM_MODE_FB_PERSIST + * + * DRM framebuffers are normally implicitly removed when their owner closes the + * DRM FD. Passing this flag will make the framebuffer persistent: it will not + * be implicitly removed. This is useful to implement flicker-free transitions + * between two processes. + * + * This flag doesn't change the behavior of &DRM_IOCTL_MODE_RMFB. + * + * User-space should ensure the framebuffer doesn't expose any sensitive user + * information: persistent framebuffers can be read back by the next DRM + * master. + */ +#define DRM_MODE_FB_PERSIST (1 << 2) struct drm_mode_fb_cmd2 { __u32 fb_id; -- 2.33.0
