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Between drm_bridge_add() and drm_bridge_remove() bridges are registered to the DRM core via the global bridge_list and visible in /sys/kernel/debug/dri/bridges. However between drm_bridge_remove() and the last drm_bridge_put() memory is still allocated even though the bridge is not registered, i.e. not in bridges_list, and also not visible in debugfs. This prevents debugging refcounted bridges lifetime, especially leaks due to a missing drm_bridge_put(). In order to allow debugfs to also show the removed bridges, move such bridges into a new ad-hoc list until they are eventually freed. Note this requires adding INIT_LIST_HEAD(&bridge->list) in the bridge initialization code. The lack of such init was not exposing any bug so far, but it would with the new code, for example when a bridge is allocated and then freed without calling drm_bridge_add(), which is common on probe errors. drm_bridge_add() needs special care for bridges being added after having been previously added and then removed. This happens for example for many non-DCS DSI host bridge drivers like samsung-dsim which drm_bridge_add/remove() themselves every time the DSI device does a DSI attaches/detach. When the DSI device is hot-pluggable this happens multiple times in the lifetime of the DSI host bridge. On every attach after the first one, drm_bridge_add() finds bridge->list in the removed list, not at the initialized state as drm_bridge_add() currently expects. Add a list_del_init() to remove the bridge from the lingering list and bring bridge->list back to the initialized state. Reviewed-by: Maxime Ripard <mripard@kernel.org> Link: https://lore.kernel.org/r/20250915-drm-bridge-debugfs-removed-v9-1-6e5c0aff5de9@bootlin.com Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.