On Fri, 11 Dec 2020 13:06:17 +0000 Simon Ser contact@emersion.fr wrote:

If a CRTC is missing a legacy primary plane pointer, a lot of things will be broken for user-space: fbdev stops working and the entire legacy uAPI stops working.

Require all drivers to populate drm_crtc.primary to prevent these issues. Warn if it's NULL.

Signed-off-by: Simon Ser contact@emersion.fr Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch Cc: Pekka Paalanen ppaalanen@gmail.com

Acked-by: Pekka Paalanen pekka.paalanen@collabora.com

---

drivers/gpu/drm/drm_mode_config.c | 3 +++ drivers/gpu/drm/drm_plane.c | 2 +- 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c index 2c73a60e8765..fbe680035129 100644 --- a/drivers/gpu/drm/drm_mode_config.c +++ b/drivers/gpu/drm/drm_mode_config.c @@ -639,6 +639,9 @@ void drm_mode_config_validate(struct drm_device *dev) }

drm_for_each_crtc(crtc, dev) {

• WARN(!crtc->primary, "Missing primary plane on [CRTC:%d:%s]\n",
  

•      crtc->base.id, crtc->name);
  

• if (crtc->primary) { WARN(!(crtc->primary->possible_crtcs & BIT(crtc->index)), "Bogus primary plane possible_crtcs: [PLANE:%d:%s] must be compatible with [CRTC:%d:%s]\n",

diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c index 5d33ca9f0032..49b0a8b9ac02 100644 --- a/drivers/gpu/drm/drm_plane.c +++ b/drivers/gpu/drm/drm_plane.c @@ -57,7 +57,7 @@

• Legacy uAPI doesn't expose the primary and cursor planes directly. DRM core
• relies on the driver to set the primary and optionally the cursor plane used
• for legacy IOCTLs. This is done by calling drm_crtc_init_with_planes(). All

• • drivers should provide one primary plane per CRTC to avoid surprising legacy

• • drivers must provide one primary plane per CRTC to avoid surprising legacy
  • userspace too much.
  */