This series adds drm_bridge_get/put() calls for DRM bridges used when
looping over bridges in an encoder chain.
This is part of the work towards removal of bridges from a still existing
DRM pipeline without use-after-free. The grand plan was discussed in [1].
Here's the work breakdown (➜ marks the current series):
1. ➜ add refcounting to DRM bridges (struct drm_bridge)
(based on devm_drm_bridge_alloc() [0])
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. ✔ add get/put to drm_bridge_add/remove() + attach/detach()
and warn on old allocation pattern (now in drm-misc-next)
E. ➜ add get/put on drm_bridge accessors
1. ✔ drm_bridge_chain_get_first_bridge() + add a cleanup action
2. … drm_bridge_get_prev_bridge()
3. … drm_bridge_get_next_bridge()
4. ➜ drm_for_each_bridge_in_chain()
5. drm_bridge_connector_init
6. of_drm_find_bridge
7. drm_of_find_panel_or_bridge, *_of_get_bridge
F. debugfs improvements
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)
Most loops are based on drm_for_each_bridge_in_chain(), so add a scoped
variant that does not use an externally-declared iterator variable and
ensures that a reference to the bridge pointed to by the iterator is
taken/released before/after every iteration (and when breaking out of the
loop).
All conversions are trivial except for drm_bridge_connector_init() which
needs some preliminary cleanups (patches 1-2).
omapdrm/omap_encoder.c is the only driver iterating over the encoder bridge
chain starting from a specific bridge, instead of iterating over the whole
list. For this use case, add a drm_for_each_bridge_in_chain_from() variant.
This series depends on two fixes to bridge-connector:
* commit 103578241512 ("drm/bridge-connector: Fix bridge in
drm_connector_hdmi_audio_init()"), currently in drm/drm-fixes, not yet
on drm-misc*
* "drm/display: bridge-connector: correct CEC bridge pointers in
drm_bridge_connector_init"
(https://lore.kernel.org/lkml/20250719-fix-cec-bridges-v1-1-a60b1333c...@oss.qualcomm.com/),
not yet applied
[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
Signed-off-by: Luca Ceresoli <luca.ceres...@bootlin.com>
---
Luca Ceresoli (9):
drm/display: bridge-connector: use scope-specific variable for the bridge
pointer
drm/display: bridge-connector: remove unused variable assignment
drm/bridge: add drm_for_each_bridge_in_chain_scoped()
drm/display: bridge-connector: use drm_for_each_bridge_in_chain_scoped()
drm/atomic: use drm_for_each_bridge_in_chain_scoped()
drm/bridge: use drm_for_each_bridge_in_chain_scoped()
drm/bridge: remove drm_for_each_bridge_in_chain()
drm/bridge: add drm_for_each_bridge_in_chain_from()
drm/omap: use drm_for_each_bridge_in_chain_from()
.clang-format | 2 +-
drivers/gpu/drm/display/drm_bridge_connector.c | 13 +++----
drivers/gpu/drm/drm_atomic.c | 3 +-
drivers/gpu/drm/drm_bridge.c | 3 +-
drivers/gpu/drm/omapdrm/omap_encoder.c | 4 +-
include/drm/drm_bridge.h | 52 ++++++++++++++++++++++++--
6 files changed, 58 insertions(+), 19 deletions(-)
---
base-commit: 46c366851a0b2159bdb97afcac04e5dec0cf09e8
change-id: 20250718-drm-bridge-alloc-getput-for_each_bridge-f141ae17b65a
prerequisite-change-id: 20250718-fix-cec-bridges-245d334d3712:v1
prerequisite-patch-id: df6d3d4a62c942703fab374bee85c49e4ac259cc
prerequisite-message-id: <20250620011616.118-1-ker...@airkyi.com>
prerequisite-patch-id: ba5a6a15ea02bcee387db0e92ffb4cd0e1fbf816
Best regards,
--
Luca Ceresoli <luca.ceres...@bootlin.com>
