drm/panel: find_panel_by_fwnode() return a counted reference

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find_panel_by_fwnode() is the fwnode-based counterpart to
of_drm_find_panel(), used internally by drm_panel_add_follower().
Like of_drm_find_panel(), it returned an unrefcounted pointer,
leaving a window where the panel could be freed between the lookup
and first use.

drm_panel_add_follower() worked around the missing panel kref by
calling get_device() on the panel's underlying struct device.
However, get_device() only prevents the device kobject from being freed.
It does not prevent the panel's kzalloc()'d container memory from being
released when the kref reaches zero.

Apply the same fix: call drm_panel_get() under panel_lock before
returning. Since find_panel_by_fwnode() now transfers a counted
reference to drm_panel_add_follower(), drm_panel_remove_follower()
must balance it with a matching drm_panel_put().

Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Albert Esteve <aesteve@redhat.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patch.msgid.link/20260717-drm_refcount_wiring-v3-4-023900c32e01@redhat.com

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Albert Esteve 2026-07-17 16:02:07 +02:00 • committed by Neil Armstrong

parent b71a623598

commit ac3baea883

2 changed files with 731 additions and 1 deletions

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10

drivers/gpu/drm/drm_panel.c

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722

drivers/gpu/drm/drm_panel.c.orig

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