Hi Maxime, On Tue, 8 Apr 2025 17:51:08 +0200 Maxime Ripard <mrip...@kernel.org> wrote:
> Hi, > > On Mon, Apr 07, 2025 at 05:27:39PM +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.ceres...@bootlin.com> [...] > > --- a/drivers/gpu/drm/bridge/panel.c > > +++ b/drivers/gpu/drm/bridge/panel.c > > @@ -287,15 +287,14 @@ struct drm_bridge *drm_panel_bridge_add_typed(struct > > drm_panel *panel, > > if (!panel) > > return ERR_PTR(-EINVAL); > > > > - panel_bridge = devm_kzalloc(panel->dev, sizeof(*panel_bridge), > > - GFP_KERNEL); > > - if (!panel_bridge) > > - return ERR_PTR(-ENOMEM); > > + panel_bridge = devm_drm_bridge_alloc(panel->dev, struct panel_bridge, > > bridge, > > + &panel_bridge_bridge_funcs); > > + if (IS_ERR(panel_bridge)) > > + return (void *)panel_bridge; > > > > panel_bridge->connector_type = connector_type; > > panel_bridge->panel = panel; > > > > - panel_bridge->bridge.funcs = &panel_bridge_bridge_funcs; > > panel_bridge->bridge.of_node = panel->dev->of_node; > > panel_bridge->bridge.ops = DRM_BRIDGE_OP_MODES; > > panel_bridge->bridge.type = connector_type; > > @@ -327,7 +326,7 @@ void drm_panel_bridge_remove(struct drm_bridge *bridge) > > panel_bridge = drm_bridge_to_panel_bridge(bridge); > > > > drm_bridge_remove(bridge); > > - devm_kfree(panel_bridge->panel->dev, bridge); > > + devm_drm_put_bridge(panel_bridge->panel->dev, bridge); > > } > > EXPORT_SYMBOL(drm_panel_bridge_remove); > > I'm fine with it on principle, but as a temporary measure. > > Now that we have the panel allocation function in place, we can just > allocate a bridge for each panel and don't need drm_panel_bridge_add_* > at all. > > As I was saying before, it doesn't need to happen right now, or before > the rest of your work for hotplug goes in. But this needs to be tackled > at some point. I totally agree this needs to be handled eventually, and also to get there in steps. The current status of this driver is not ideal, so I paid attention to not make it unnecessarily worse when writing this patch. Do you think the current patch is OK for the next step? I'm going to send v2 in a few hours, so don't hesitate to mention any improvements you deem necessary. Luca -- Luca Ceresoli, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
