Re: [PATCH 02/10] drm/bridge: Add a function to abstract away panels

Hi Maxime,

On Tue, Jul 20, 2021 at 03:45:17PM +0200, Maxime Ripard wrote:

Display drivers so far need to have a lot of boilerplate to first retrieve either the panel or bridge that they are connected to using drm_of_find_panel_or_bridge(), and then either deal with each with ad-hoc functions or create a drm panel bridge through drm_panel_bridge_add.

In order to reduce the boilerplate and hopefully create a path of least resistance towards using the DRM panel bridge layer, let's create the function devm_drm_of_get_next to reduce that boilerplate.

Signed-off-by: Maxime Ripard maxime@cerno.tech

drivers/gpu/drm/drm_bridge.c | 62 +++++++++++++++++++++++++++++++++--- drivers/gpu/drm/drm_of.c | 3 ++ include/drm/drm_bridge.h | 2 ++ 3 files changed, 63 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c index 044acd07c153..aef8c9f4fb9f 100644 --- a/drivers/gpu/drm/drm_bridge.c +++ b/drivers/gpu/drm/drm_bridge.c @@ -24,10 +24,12 @@ #include <linux/err.h> #include <linux/module.h> #include <linux/mutex.h> +#include <linux/of_graph.h>

#include <drm/drm_atomic_state_helper.h> #include <drm/drm_bridge.h> #include <drm/drm_encoder.h> +#include <drm/drm_panel.h>

#include "drm_crtc_internal.h"

@@ -50,10 +52,8 @@

• Display drivers are responsible for linking encoders with the first bridge
• in the chains. This is done by acquiring the appropriate bridge with

• • of_drm_find_bridge() or drm_of_find_panel_or_bridge(), or creating it for a
• • panel with drm_panel_bridge_add_typed() (or the managed version
• • devm_drm_panel_bridge_add_typed()). Once acquired, the bridge shall be
• • attached to the encoder with a call to drm_bridge_attach().

• • drm_of_get_next(). Once acquired, the bridge shall be attached to the
• • encoder with a call to drm_bridge_attach().
  • Bridges are responsible for linking themselves with the next bridge in the
  • chain, if any. This is done the same way as for encoders, with the call to

@@ -1223,6 +1223,60 @@ struct drm_bridge *of_drm_find_bridge(struct device_node *np) return NULL; } EXPORT_SYMBOL(of_drm_find_bridge);

+/**

• • devm_drm_of_get_next - Return next bridge in the chain

I would prefer a more IMO descriptive name - something like this:

devm_drm_of_get_bridge - Return a bridge or a panel wrapped as a bridge

• • @dev: device to tie the bridge lifetime to
• • @np: device tree node containing encoder output ports
• • @port: port in the device tree node
• • @endpoint: endpoint in the device tree node
• • Given a DT node's port and endpoint number, finds the connected node
• • and returns the associated bridge if any, or creates and returns a
• • drm panel bridge instance if a panel is connected.
• • Returns a pointer to the bridge if successful, or an error pointer
• • otherwise.
• */

+struct drm_bridge *devm_drm_of_get_next(struct device *dev,

• 			struct device_node *np,
  

• 			unsigned int port,
  

• 			unsigned int endpoint)
  

+{

• struct device_node *remote;
• struct drm_bridge *bridge;
• struct drm_panel *panel;
• /*

• * 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
  

• * device-tree node.
  

• */
  

• if (!of_graph_is_present(np))

• return ERR_PTR(-ENODEV);
  

• remote = of_graph_get_remote_node(np, port, endpoint);
• if (!remote)

• return ERR_PTR(-ENODEV);
  

• bridge = of_drm_find_bridge(remote);
• if (bridge) {

• of_node_put(remote);
  

• return bridge;
  

• }
• panel = of_drm_find_panel(remote);
• if (IS_ERR(panel)) {

• of_node_put(remote);
  

• return ERR_CAST(panel);
  

• }

Here panel may be NULL which is unhadled, as devm_drm_panel_bridge_add() will fault if the passed panel pointer is NULL.

Sam

• of_node_put(remote);
• return devm_drm_panel_bridge_add(dev, panel);

+} +EXPORT_SYMBOL(devm_drm_of_get_next); #endif

MODULE_AUTHOR("Ajay Kumar ajaykumar.rs@samsung.com"); diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c index 997b8827fed2..bbbdc4d17ac9 100644 --- a/drivers/gpu/drm/drm_of.c +++ b/drivers/gpu/drm/drm_of.c @@ -231,6 +231,9 @@ EXPORT_SYMBOL_GPL(drm_of_encoder_active_endpoint);

• return either the associated struct drm_panel or drm_bridge device. Either
• @panel or @bridge must not be NULL.

• • This function is deprecated and should not be used in new drivers. Use
• • drm_of_get_next() instead.
• • Returns zero if successful, or one of the standard error codes if it fails.
  */

int drm_of_find_panel_or_bridge(const struct device_node *np, diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h index 46bdfa48c413..e16fafc6f37d 100644 --- a/include/drm/drm_bridge.h +++ b/include/drm/drm_bridge.h @@ -911,6 +911,8 @@ struct drm_bridge *devm_drm_panel_bridge_add(struct device *dev, struct drm_bridge *devm_drm_panel_bridge_add_typed(struct device *dev, struct drm_panel *panel, u32 connector_type); +struct drm_bridge *devm_drm_of_get_next(struct device *dev, struct device_node *node,

• 			unsigned int port, unsigned int endpoint);
  

struct drm_connector *drm_panel_bridge_connector(struct drm_bridge *bridge); #endif

-- 2.31.1