Hi Maxime, On Tue, 19 Aug 2025 15:47:06 +0200 Maxime Ripard <mrip...@kernel.org> wrote:
> > +/** > > + * 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); \ > > So my understanding is that the initial value of bridge would be cleaned > up with drm_bridge_put... > > > + bridge; \ > > + bridge = drm_bridge_get_next_bridge_and_put(bridge)) > > ... but also when iterating? > > So if we have more than 0 values, we put two references? No, this is not the case. The __free action is executed only when exiting the entire for loop, not a single iteration. This is consistent with the fact that the loop variable is persistent across iterations. I tested this macro in both cases: * looping over the entire chain the final value of @bridge will be NULL and the cleanup action won't call drm_bridge_put() * breaking before the last element, @bridge is non-NULL and the cleanup action does call drm_bridge_put() See examples such as for_each_child_of_node_scoped() and other OF iterators which work in the same way (which is no coincidence, I used them as starting point for writing this patch). Best regards, Luca -- Luca Ceresoli, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
