drm/panel: Flesh out kerneldoc

Write more complete kerneldoc comments for the DRM panel API and
integrate the helpers in the DRM DocBook reference.

Signed-off-by: Thierry Reding <treding@nvidia.com>

3 files changed, 126 insertions, 0 deletions

diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index 8a0b2a84f4b..4a2682f1eca 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -2431,6 +2431,12 @@ void intel_crt_init(struct drm_device *dev)
 	  <title>Tile group</title>
 !Pdrivers/gpu/drm/drm_crtc.c Tile group
     </sect2>
+    <sect2>
+      <title>Panel Helper Reference</title>
+!Iinclude/drm/drm_panel.h
+!Edrivers/gpu/drm/drm_panel.c
+!Pdrivers/gpu/drm/drm_panel.c drm panel
+    </sect2>
   </sect1>
 
   <!-- Internals: kms properties -->
diff --git a/drivers/gpu/drm/drm_panel.c b/drivers/gpu/drm/drm_panel.c
index 2ef988e037b..3dfe3c88650 100644
--- a/drivers/gpu/drm/drm_panel.c
+++ b/drivers/gpu/drm/drm_panel.c
@@ -30,12 +30,36 @@
 static DEFINE_MUTEX(panel_lock);
 static LIST_HEAD(panel_list);
 
+/**
+ * DOC: drm panel
+ *
+ * The DRM panel helpers allow drivers to register panel objects with a
+ * central registry and provide functions to retrieve those panels in display
+ * drivers.
+ */
+
+/**
+ * drm_panel_init - initialize a panel
+ * @panel: DRM panel
+ *
+ * Sets up internal fields of the panel so that it can subsequently be added
+ * to the registry.
+ */
 void drm_panel_init(struct drm_panel *panel)
 {
 	INIT_LIST_HEAD(&panel->list);
 }
 EXPORT_SYMBOL(drm_panel_init);
 
+/**
+ * drm_panel_add - add a panel to the global registry
+ * @panel: panel to add
+ *
+ * Add a panel to the global registry so that it can be looked up by display
+ * drivers.
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
 int drm_panel_add(struct drm_panel *panel)
 {
 	mutex_lock(&panel_lock);
@@ -46,6 +70,12 @@ int drm_panel_add(struct drm_panel *panel)
 }
 EXPORT_SYMBOL(drm_panel_add);
 
+/**
+ * drm_panel_remove - remove a panel from the global registry
+ * @panel: DRM panel
+ *
+ * Removes a panel from the global registry.
+ */
 void drm_panel_remove(struct drm_panel *panel)
 {
 	mutex_lock(&panel_lock);
@@ -54,6 +84,18 @@ void drm_panel_remove(struct drm_panel *panel)
 }
 EXPORT_SYMBOL(drm_panel_remove);
 
+/**
+ * drm_panel_attach - attach a panel to a connector
+ * @panel: DRM panel
+ * @connector: DRM connector
+ *
+ * After obtaining a pointer to a DRM panel a display driver calls this
+ * function to attach a panel to a connector.
+ *
+ * An error is returned if the panel is already attached to another connector.
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
 int drm_panel_attach(struct drm_panel *panel, struct drm_connector *connector)
 {
 	if (panel->connector)
@@ -66,6 +108,15 @@ int drm_panel_attach(struct drm_panel *panel, struct drm_connector *connector)
 }
 EXPORT_SYMBOL(drm_panel_attach);
 
+/**
+ * drm_panel_detach - detach a panel from a connector
+ * @panel: DRM panel
+ *
+ * Detaches a panel from the connector it is attached to. If a panel is not
+ * attached to any connector this is effectively a no-op.
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
 int drm_panel_detach(struct drm_panel *panel)
 {
 	panel->connector = NULL;
@@ -76,6 +127,16 @@ int drm_panel_detach(struct drm_panel *panel)
 EXPORT_SYMBOL(drm_panel_detach);
 
 #ifdef CONFIG_OF
+/**
+ * of_drm_find_panel - look up a panel using a device tree node
+ * @np: device tree node of the panel
+ *
+ * Searches the set of registered panels for one that matches the given device
+ * tree node. If a matching panel is found, return a pointer to it.
+ *
+ * Return: A pointer to the panel registered for the specified device tree
+ * node or NULL if no panel matching the device tree node can be found.
+ */
 struct drm_panel *of_drm_find_panel(struct device_node *np)
 {
 	struct drm_panel *panel;
diff --git a/include/drm/drm_panel.h b/include/drm/drm_panel.h
index 1fbcc96063a..b88b4dcd698 100644
--- a/include/drm/drm_panel.h
+++ b/include/drm/drm_panel.h
@@ -70,6 +70,14 @@ struct drm_panel_funcs {
 	int (*get_modes)(struct drm_panel *panel);
 };
 
+/**
+ * struct drm_panel - DRM panel object
+ * @drm: DRM device owning the panel
+ * @connector: DRM connector that the panel is attached to
+ * @dev: parent device of the panel
+ * @funcs: operations that can be performed on the panel
+ * @list: panel entry in registry
+ */
 struct drm_panel {
 	struct drm_device *drm;
 	struct drm_connector *connector;
@@ -80,6 +88,17 @@ struct drm_panel {
 	struct list_head list;
 };
 
+/**
+ * drm_disable_unprepare - power off a panel
+ * @panel: DRM panel
+ *
+ * Calling this function will completely power off a panel (assert the panel's
+ * reset, turn off power supplies, ...). After this function has completed, it
+ * is usually no longer possible to communicate with the panel until another
+ * call to drm_panel_prepare().
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
 static inline int drm_panel_unprepare(struct drm_panel *panel)
 {
 	if (panel && panel->funcs && panel->funcs->unprepare)
@@ -88,6 +107,16 @@ static inline int drm_panel_unprepare(struct drm_panel *panel)
 	return panel ? -ENOSYS : -EINVAL;
 }
 
+/**
+ * drm_panel_disable - disable a panel
+ * @panel: DRM panel
+ *
+ * This will typically turn off the panel's backlight or disable the display
+ * drivers. For smart panels it should still be possible to communicate with
+ * the integrated circuitry via any command bus after this call.
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
 static inline int drm_panel_disable(struct drm_panel *panel)
 {
 	if (panel && panel->funcs && panel->funcs->disable)
@@ -96,6 +125,16 @@ static inline int drm_panel_disable(struct drm_panel *panel)
 	return panel ? -ENOSYS : -EINVAL;
 }
 
+/**
+ * drm_panel_prepare - power on a panel
+ * @panel: DRM panel
+ *
+ * Calling this function will enable power and deassert any reset signals to
+ * the panel. After this has completed it is possible to communicate with any
+ * integrated circuitry via a command bus.
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
 static inline int drm_panel_prepare(struct drm_panel *panel)
 {
 	if (panel && panel->funcs && panel->funcs->prepare)
@@ -104,6 +143,16 @@ static inline int drm_panel_prepare(struct drm_panel *panel)
 	return panel ? -ENOSYS : -EINVAL;
 }
 
+/**
+ * drm_panel_enable - enable a panel
+ * @panel: DRM panel
+ *
+ * Calling this function will cause the panel display drivers to be turned on
+ * and the backlight to be enabled. Content will be visible on screen after
+ * this call completes.
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
 static inline int drm_panel_enable(struct drm_panel *panel)
 {
 	if (panel && panel->funcs && panel->funcs->enable)
@@ -112,6 +161,16 @@ static inline int drm_panel_enable(struct drm_panel *panel)
 	return panel ? -ENOSYS : -EINVAL;
 }
 
+/**
+ * drm_panel_get_modes - probe the available display modes of a panel
+ * @panel: DRM panel
+ *
+ * The modes probed from the panel are automatically added to the connector
+ * that the panel is attached to.
+ *
+ * Return: The number of modes available from the panel on success or a
+ * negative error code on failure.
+ */
 static inline int drm_panel_get_modes(struct drm_panel *panel)
 {
 	if (panel && panel->funcs && panel->funcs->get_modes)