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b=TQCzqL3+kCjx4SA5fD1konBZlj2IajoWgIOf6zPBg8IO7fhPhIvu/SYYYr7cVKDI7 3/dW/L/TO8mlgbRq2ax0skkFC1DQNkqdEXZbPLae94bHTmcvKdPyEYSDilbBbBmJhz MCp/TuRjYZcIuWlrg+MoM6CpGRfi/fc2y7C5XNGs= Date: Mon, 4 May 2026 17:55:36 +0300 From: Laurent Pinchart To: Luca Ceresoli Cc: Andrzej Hajda , Neil Armstrong , Robert Foss , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Rob Clark , Dmitry Baryshkov , Abhinav Kumar , Jessica Zhang , Sean Paul , Marijn Suijten , Sumit Semwal , John Stultz , Tomi Valkeinen , Michal Simek , Hui Pu , Ian Ray , Thomas Petazzoni , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, Dmitry Baryshkov Subject: Re: [PATCH v4 02/11] drm/bridge: add of_drm_get_bridge_by_endpoint() Message-ID: <20260504145536.GA1455860@killaraus.ideasonboard.com> References: <20260504-drm-bridge-alloc-getput-panel_or_bridge-v4-0-b578c3daaf10@bootlin.com> <20260504-drm-bridge-alloc-getput-panel_or_bridge-v4-2-b578c3daaf10@bootlin.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260504-drm-bridge-alloc-getput-panel_or_bridge-v4-2-b578c3daaf10@bootlin.com> On Mon, May 04, 2026 at 12:45:05PM +0200, Luca Ceresoli wrote: > drm_of_find_panel_or_bridge() is widely used, but many callers pass NULL > into the @panel or the @bridge arguments, thus making a very partial usage > of this rather complex function. > > Besides, the bridge returned in @bridge is not refcounted, thus making this > API unsafe when DRM bridge hotplug will be introduced. > > Solve both issues for the cases of calls to drm_of_find_panel_or_bridge() > with a NULL @panel pointer by adding a new function that only looks for > bridges (and is thus much simpler) and increments the refcount of the > returned bridge. > > The new function is identical to drm_of_find_panel_or_bridge() except it: > > - handles bridge refcounting: uses of_drm_find_and_get_bridge() instead of > of_drm_find_bridge() internally to return a refcounted bridge > - is simpler to use: just takes no @panel parameter, returns the pointer > in the return value instead of a double pointer argument > - has a simpler implementation: it is equal to > drm_of_find_panel_or_bridge() after removing the code that becomes dead > when @panel == NULL > > Also add this function to drm_bridge.c and not drm_of.c because it returns > bridges only. > > Reviewed-by: Dmitry Baryshkov > Signed-off-by: Luca Ceresoli > --- > Changes in v4: > - update function declaration in non-OF case > > Changes in v2: > - return the bridge in the return value, not a double pointer > --- > drivers/gpu/drm/drm_bridge.c | 41 +++++++++++++++++++++++++++++++++++++++++ > include/drm/drm_bridge.h | 7 +++++++ > 2 files changed, 48 insertions(+) > > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c > index 6fb71de6d22a..01f9e0426648 100644 > --- a/drivers/gpu/drm/drm_bridge.c > +++ b/drivers/gpu/drm/drm_bridge.c > @@ -1582,6 +1582,47 @@ struct drm_bridge *of_drm_find_bridge(struct device_node *np) > return bridge; > } > EXPORT_SYMBOL(of_drm_find_bridge); > + > +/** > + * of_drm_get_bridge_by_endpoint - return DRM bridge connected to a port/endpoint > + * @np: device tree node containing output ports > + * @port: port in the device tree node, or -1 for the first port found > + * @endpoint: endpoint in the device tree node, or -1 for the first endpoint found > + * > + * Given a DT node's port and endpoint number, find the connected node and > + * return the associated drm_bridge device. > + * > + * The refcount of the returned bridge is incremented. Use drm_bridge_put() > + * when done with it. > + * > + * Returns a pointer to the connected drm_bridge, or a negative error on failure > + */ > +struct drm_bridge *of_drm_get_bridge_by_endpoint(const struct device_node *np, > + int port, int endpoint) > +{ > + struct drm_bridge *bridge; > + > + /* > + * of_graph_get_remote_node() produces a noisy error message if port > + * node isn't found and the absence of the port is a legit case here, > + * so at first we silently check whether graph presents in the s/graph presents/graph is present/ Reviewed-by: Laurent Pinchart > + * device-tree node. > + */ > + if (!of_graph_is_present(np)) > + return ERR_PTR(-ENODEV); > + > + struct device_node *remote __free(device_node) = > + of_graph_get_remote_node(np, port, endpoint); > + if (!remote) > + return ERR_PTR(-ENODEV); > + > + bridge = of_drm_find_and_get_bridge(remote); > + if (!bridge) > + return ERR_PTR(-EPROBE_DEFER); > + > + return bridge; > +} > +EXPORT_SYMBOL_GPL(of_drm_get_bridge_by_endpoint); > #endif > > /** > diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h > index d6cd0f5af045..31e11a360c42 100644 > --- a/include/drm/drm_bridge.h > +++ b/include/drm/drm_bridge.h > @@ -1327,6 +1327,8 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge, > #ifdef CONFIG_OF > struct drm_bridge *of_drm_find_and_get_bridge(struct device_node *np); > struct drm_bridge *of_drm_find_bridge(struct device_node *np); > +struct drm_bridge *of_drm_get_bridge_by_endpoint(const struct device_node *np, > + int port, int endpoint); > #else > static inline struct drm_bridge *of_drm_find_and_get_bridge(struct device_node *np) > { > @@ -1336,6 +1338,11 @@ static inline struct drm_bridge *of_drm_find_bridge(struct device_node *np) > { > return NULL; > } > +static inline struct drm_bridge *of_drm_get_bridge_by_endpoint(const struct device_node *np, > + int port, int endpoint) > +{ > + return -ENODEV; > +} > #endif > > static inline bool drm_bridge_is_last(struct drm_bridge *bridge) -- Regards, Laurent Pinchart