From: Luca Ceresoli Date: Fri, 8 Aug 2025 14:49:10 +0000 (+0200) Subject: drm/bridge: add drm_for_each_bridge_in_chain_scoped() X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=e46efc6a7d288830c4aeaf3c65c7e913a8ca35d7;p=thirdparty%2Fkernel%2Flinux.git drm/bridge: add drm_for_each_bridge_in_chain_scoped() 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 Link: https://lore.kernel.org/r/20250808-drm-bridge-alloc-getput-for_each_bridge-v2-3-edb6ee81edf1@bootlin.com Signed-off-by: Luca Ceresoli --- diff --git a/.clang-format b/.clang-format index 48405c54ef271..1cac7d4976644 100644 --- a/.clang-format +++ b/.clang-format @@ -168,6 +168,7 @@ ForEachMacros: - 'drm_exec_for_each_locked_object' - 'drm_exec_for_each_locked_object_reverse' - 'drm_for_each_bridge_in_chain' + - 'drm_for_each_bridge_in_chain_scoped' - 'drm_for_each_connector_iter' - 'drm_for_each_crtc' - 'drm_for_each_crtc_reverse' diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h index 76e05930f50e0..57a3d3cd08e74 100644 --- a/include/drm/drm_bridge.h +++ b/include/drm/drm_bridge.h @@ -1440,10 +1440,51 @@ drm_bridge_chain_get_last_bridge(struct drm_encoder *encoder) * iteration * * Iterate over all bridges present in the bridge chain attached to @encoder. + * + * This is deprecated, do not use! + * New drivers shall use drm_for_each_bridge_in_chain_scoped(). */ #define drm_for_each_bridge_in_chain(encoder, bridge) \ list_for_each_entry(bridge, &(encoder)->bridge_chain, chain_node) +/** + * drm_bridge_get_next_bridge_and_put - Get the next bridge in the chain + * and put the previous + * @bridge: bridge object + * + * Same as drm_bridge_get_next_bridge() but additionally puts the @bridge. + * + * RETURNS: + * the next bridge in the chain after @bridge, or NULL if @bridge is the last. + */ +static inline struct drm_bridge * +drm_bridge_get_next_bridge_and_put(struct drm_bridge *bridge) +{ + struct drm_bridge *next = drm_bridge_get_next_bridge(bridge); + + drm_bridge_put(bridge); + + return next; +} + +/** + * drm_for_each_bridge_in_chain_scoped - iterate over all bridges attached + * to an encoder + * @encoder: the encoder to iterate bridges on + * @bridge: a bridge pointer updated to point to the current bridge at each + * iteration + * + * Iterate over all bridges present in the bridge chain attached to @encoder. + * + * Automatically gets/puts the bridge reference while iterating, and puts + * the reference even if returning or breaking in the middle of the loop. + */ +#define drm_for_each_bridge_in_chain_scoped(encoder, bridge) \ + for (struct drm_bridge *bridge __free(drm_bridge_put) = \ + drm_bridge_chain_get_first_bridge(encoder); \ + bridge; \ + bridge = drm_bridge_get_next_bridge_and_put(bridge)) + enum drm_mode_status drm_bridge_chain_mode_valid(struct drm_bridge *bridge, const struct drm_display_info *info,