[PATCH v9 0/5] drm/bridge: get/put the bridge returned by drm_bridge_chain_get_first_bridge()

[Luca Ceresoli]

This series adds drm_bridge_get/put() calls for DRM bridges returned by
drm_bridge_chain_get_first_bridge().

All patches are Reviewed-by Maxime except patch 3.

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 (this series)
       2. drm_bridge_chain_get_last_bridge()
       3. drm_bridge_get_prev_bridge()
       4. drm_bridge_get_next_bridge()
       5. drm_for_each_bridge_in_chain()
       6. drm_bridge_connector_init
       7. of_drm_find_bridge
       8. 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)

All the patches in this series have already been sent as part of the larger
"[PATCH v7 00/11] drm/bridge: add devm_drm_bridge_alloc() with bridge
refcount" series [2], hence the v9 number. They have all been Reviewed-by
Maxime too, however they could not be applied at that time, awaiting the
conversion of all bridge drivers to devm_drm_bridge_alloc(), now done (item
1.A).

I'm resending all patches to give them visibility now that they are ready
to be applied.

[0] https://gitlab.freedesktop.org/drm/misc/kernel/-/commit/0cc6aadd7fc1e629b715ea3d1ba537ef2da95eec
[1] https://lore.kernel.org/lkml/20250206-hotplug-drm-bridge-v6-0-9d6f2c9c3058@bootlin.com/t/#u
[2] https://lore.kernel.org/all/20250314-drm-bridge-refcount-v7-0-152571f8c694@bootlin.com/

Signed-off-by: Luca Ceresoli <luca.ceresoli at bootlin.com>
---
Changes in v9:
- Small improvement to patch 3
- Link to v8: https://lore.kernel.org/r/20250620-drm-bridge-alloc-getput-drm_bridge_chain_get_first_bridge-v8-0-0321845fcafb@bootlin.com

Changes in v8:
- rebased on current drm-misc-next
- Patch 4: reworked based on current code
- Link to v7: https://lore.kernel.org/all/20250314-drm-bridge-refcount-v7-0-152571f8c694@bootlin.com/

---
Luca Ceresoli (5):
      drm/bridge: add a cleanup action for scope-based drm_bridge_put() invocation
      drm/bridge: get the bridge returned by drm_bridge_chain_get_first_bridge()
      drm/mxsfb: put the bridge returned by drm_bridge_chain_get_first_bridge()
      drm/atomic-helper: put the bridge returned by drm_bridge_chain_get_first_bridge()
      drm/probe-helper: put the bridge returned by drm_bridge_chain_get_first_bridge()

 drivers/gpu/drm/drm_atomic_helper.c |  7 +++++++
 drivers/gpu/drm/drm_probe_helper.c  |  1 +
 drivers/gpu/drm/mxsfb/lcdif_kms.c   |  4 ++--
 include/drm/drm_bridge.h            | 11 +++++++++--
 4 files changed, 19 insertions(+), 4 deletions(-)
---
base-commit: e21354aea4b4420b53c44e36828607a7c94a994c
change-id: 20250620-drm-bridge-alloc-getput-drm_bridge_chain_get_first_bridge-be39c442dcd6

Best regards,
-- 
Luca Ceresoli <luca.ceresoli at bootlin.com>