Hi Maxime, On Mon, 28 Apr 2025 13:39:23 +0200 Maxime Ripard <mripard@xxxxxxxxxx> wrote: > On Thu, Apr 24, 2025 at 10:05:49PM +0200, Luca Ceresoli wrote: > > This is the new API for allocating DRM bridges. > > > > The devm lifetime management of this driver is peculiar. The underlying > > device for the panel_bridge is the panel, and the devm lifetime is tied the > > panel device (panel->dev). However the panel_bridge allocation is not > > performed by the panel driver, but rather by a separate entity (typically > > the previous bridge in the encoder chain). > > > > Thus when that separate entoty is destroyed, the panel_bridge is not > > removed automatically by devm, so it is rather done explicitly by calling > > drm_panel_bridge_remove(). This is the function that does devm_kfree() the > > panel_bridge in current code, so update it as well to put the bridge > > reference instead. > > > > Signed-off-by: Luca Ceresoli <luca.ceresoli@xxxxxxxxxxx> > > This looks fine, but we need a TODO entry to clean this up later on, and > a comment on devm_drm_put_bridge that this is inherently unsafe and > must not be used. Ah, I see, OK. Quick draft: /** * devm_drm_put_bridge - Release a bridge reference obtained via devm * @dev: device that got the bridge via devm * @bridge: pointer to a struct drm_bridge obtained via devm * * Same as drm_bridge_put() for bridge pointers obtained via devm functions * such as devm_drm_bridge_alloc(). + * + * This function is a temporary workaround and MUST NOT be used. Manual + * handling of bridge lifetime is inherently unsafe. */ and: - devm_kfree(panel_bridge->panel->dev, bridge); + /* TODO remove this after reworking panel_bridge lifetime */ + devm_drm_put_bridge(panel_bridge->panel->dev, bridge); } Does it look good enough? Luca -- Luca Ceresoli, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
