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To support hot-unplug of this bridge we need to protect access to device
resources in case sn65dsi83_remove() happens concurrently to other code.
Some care is needed for the case when the unplug happens before
sn65dsi83_atomic_disable() has a chance to enter the critical section
(i.e. a successful drm_bridge_enter() call), which occurs whenever the
hardware is removed while the display is active. When that happens,
sn65dsi83_atomic_disable() in unable to release the resources taken by
sn65dsi83_atomic_pre_enable().
To ensure those resources are released exactly once on device removal:
* move the code to release them to a dedicated function
* register that function when the resources are taken in
sn65dsi83_atomic_pre_enable()
* if sn65dsi83_atomic_disable() happens before sn65dsi83_remove()
(typical non-hot-unplug case):
* sn65dsi83_atomic_disable() can enter the critical section
(drm_bridge_enter() returns 0) -> it releases and executes the
devres action
* if sn65dsi83_atomic_disable() happens after sn65dsi83_remove()
(typical hot-unplug case):
* sn65dsi83_remove() -> drm_bridge_unplug() prevents
sn65dsi83_atomic_disable() from entering the critical section
(drm_bridge_enter() returns nonzero), so sn65dsi83_atomic_disable()
cannot release and execute the devres action
* the devres action is executed at the end of sn65dsi83_remove()
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Link: https://patch.msgid.link/20251112-drm-bridge-atomic-vs-remove-v3-2-85db717ce094@bootlin.com
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
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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.