This small series adds drm_bridge_get/put() calls where applicable in the
bridge core code, and adds a warning when the old allocation patter is
used.
This is part of the work towards removal of bridges from a still existing
DRM pipeline without use-after-free.
The steps in the grand plan [1] are:
1. ➜ add refcounting to DRM bridges (struct drm_bridge)
2. handle gracefully atomic updates during bridge removal
3. avoid DSI host drivers to have dangling pointers to DSI devices
4. finish the hotplug bridge work, removing the "always-disconnected"
connector, moving code to the core and potentially removing the
hotplug-bridge itself (this needs to be clarified as points 1-3 are
developed)
This series is part of step 1 of the grand plan.
Current tasks in step 1 of the grand plan:
A. ✔ add new alloc API and refcounting (in v6.16-rc1)
B. ✔ convert all bridge drivers to new API (now in drm-misc-next)
C. ✔ kunit tests (now in drm-misc-next)
D. ➜ after (B), add get/put to drm_bridge_add/remove() + attach/detech()
and warn on old allocation pattern (this series)
E. after (B), convert accessors; this is a large work and can be done
in chunks
F. debugfs improvements
Specifically, this series does two things related to the recently
introduced devm_drm_bridge_alloc() [0]:
A) add drm_bridge_get/put() in the two places within drm_bridge.c where a
bridge reference is taken/relased
B) add a warning on bridges using the old allocation pattern instead of
devm_drm_bridge_alloc()
These are loosely related topics, but I'm sending them in a single series
to avoid trivial patch conflicts, as they touch the same lines. This will
holefully help getting the patches applied more efficiently and quickly. I
hope this is fine being 3 small patches.
Part A) is made of patches 1 and 2. Those have been previously sent in
"[PATCH v7 00/11] drm/bridge: add devm_drm_bridge_alloc() with bridge
refcount" [2] (as patches 3 and 4), and already Reviewed-by Maxime at that
time. However they could not be applied until the conversion of all bridge
drivers to devm_drm_bridge_alloc(), which got completed a few days
ago. Hence the reason this is v8.
[0]
https://gitlab.freedesktop.org/drm/misc/kernel/-/commit/0cc6aadd7fc1e629b715ea3d1ba537ef2da95eec
[1]
https://lore.kernel.org/lkml/20250206-hotplug-drm-bridge-v6-0-9d6f2c9c3...@bootlin.com/t/#u
[2]
https://lore.kernel.org/all/20250314-drm-bridge-refcount-v7-0-152571f8c...@bootlin.com/
Signed-off-by: Luca Ceresoli <luca.ceres...@bootlin.com>
---
Luca Ceresoli (3):
drm/bridge: get/put the bridge reference in drm_bridge_add/remove()
drm/bridge: get/put the bridge reference in drm_bridge_attach/detach()
drm/bridge: add warning for bridges not using devm_drm_bridge_alloc()
drivers/gpu/drm/drm_bridge.c | 24 ++++++++++++++++++++----
1 file changed, 20 insertions(+), 4 deletions(-)
---
base-commit: a59a271769149f0b8258507276f3d2a24370cbdb
change-id: 20250620-drm-bridge-alloc-getput-drm-bridge-c-0ab2ca481c37
Best regards,
--
Luca Ceresoli <luca.ceres...@bootlin.com>
