drm/bridge: add drm_for_each_bridge_in_chain_scoped()

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drm_for_each_bridge_in_chain() iterates ofer the bridges in an encoder
chain without protecting the lifetime of the bridges using
drm_bridge_get/put(). This creates a risk window where the bridge could be
freed while iterating on it. Users of drm_for_each_bridge_in_chain() cannot
solve this reliably.

Add variant of drm_for_each_bridge_in_chain() that gets/puts the bridge
reference at the beginning/end of each iteration, and puts it if breaking
ot of the loop.

Note that this requires adding a new drm_bridge_get_next_bridge_and_put()
function because, unlike similar functions as __of_get_next_child(),
drm_bridge_get_next_bridge() gets the "next" pointer but does not put the
"prev" pointer. Unfortunately drm_bridge_get_next_bridge() cannot be
modified to put the "prev" pointer because some of its users rely on
this, such as drm_atomic_bridge_propagate_bus_flags().

Also deprecate drm_for_each_bridge_in_chain(), in preparation for removing
it after converting all users to the scoped version.

Reviewed-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20250808-drm-bridge-alloc-getput-for_each_bridge-v2-3-edb6ee81edf1@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

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This commit is contained in:

Luca Ceresoli 2025-08-08 16:49:10 +02:00

parent c92f59bac0

commit e46efc6a7d

2 changed files with 42 additions and 0 deletions

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.clang-format

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41

include/drm/drm_bridge.h

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