drm/doc: Polish docs for drm_property&drm_property_blob

- remove kerneldoc for drm-internal functions
- drm_property_replace_global_blob isn't actually atomic, and doesn't
  need to be. Update docs&comments to match
- document all the types and try to link things a bit better
- nits all over

v2: Appease checkpatch in the moved code (Archit)
Reviewed-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160829082757.17913-9-daniel.vetter@ffwll.ch

Documentation/gpu/drm-kms.rst

@@ -304,94 +304,12 @@ KMS Locking
 KMS Properties
 ==============
 
-Drivers may need to expose additional parameters to applications than
-those described in the previous sections. KMS supports attaching
-properties to CRTCs, connectors and planes and offers a userspace API to
-list, get and set the property values.
-
-Properties are identified by a name that uniquely defines the property
-purpose, and store an associated value. For all property types except
-blob properties the value is a 64-bit unsigned integer.
-
-KMS differentiates between properties and property instances. Drivers
-first create properties and then create and associate individual
-instances of those properties to objects. A property can be instantiated
-multiple times and associated with different objects. Values are stored
-in property instances, and all other property information are stored in
-the property and shared between all instances of the property.
-
-Every property is created with a type that influences how the KMS core
-handles the property. Supported property types are
-
-DRM_MODE_PROP_RANGE
-    Range properties report their minimum and maximum admissible values.
-    The KMS core verifies that values set by application fit in that
-    range.
-
-DRM_MODE_PROP_ENUM
-    Enumerated properties take a numerical value that ranges from 0 to
-    the number of enumerated values defined by the property minus one,
-    and associate a free-formed string name to each value. Applications
-    can retrieve the list of defined value-name pairs and use the
-    numerical value to get and set property instance values.
-
-DRM_MODE_PROP_BITMASK
-    Bitmask properties are enumeration properties that additionally
-    restrict all enumerated values to the 0..63 range. Bitmask property
-    instance values combine one or more of the enumerated bits defined
-    by the property.
-
-DRM_MODE_PROP_BLOB
-    Blob properties store a binary blob without any format restriction.
-    The binary blobs are created as KMS standalone objects, and blob
-    property instance values store the ID of their associated blob
-    object.
-
-    Blob properties are only used for the connector EDID property and
-    cannot be created by drivers.
-
-To create a property drivers call one of the following functions
-depending on the property type. All property creation functions take
-property flags and name, as well as type-specific arguments.
-
--  struct drm_property \*drm_property_create_range(struct
-   drm_device \*dev, int flags, const char \*name, uint64_t min,
-   uint64_t max);
-   Create a range property with the given minimum and maximum values.
-
--  struct drm_property \*drm_property_create_enum(struct drm_device
-   \*dev, int flags, const char \*name, const struct
-   drm_prop_enum_list \*props, int num_values);
-   Create an enumerated property. The ``props`` argument points to an
-   array of ``num_values`` value-name pairs.
-
--  struct drm_property \*drm_property_create_bitmask(struct
-   drm_device \*dev, int flags, const char \*name, const struct
-   drm_prop_enum_list \*props, int num_values);
-   Create a bitmask property. The ``props`` argument points to an array
-   of ``num_values`` value-name pairs.
-
-Properties can additionally be created as immutable, in which case they
-will be read-only for applications but can be modified by the driver. To
-create an immutable property drivers must set the
-DRM_MODE_PROP_IMMUTABLE flag at property creation time.
-
-When no array of value-name pairs is readily available at property
-creation time for enumerated or range properties, drivers can create the
-property using the :c:func:`drm_property_create()` function and
-manually add enumeration value-name pairs by calling the
-:c:func:`drm_property_add_enum()` function. Care must be taken to
-properly specify the property type through the ``flags`` argument.
-
-After creating properties drivers can attach property instances to CRTC,
-connector and plane objects by calling the
-:c:func:`drm_object_attach_property()`. The function takes a
-pointer to the target object, a pointer to the previously created
-property and an initial instance value.
-
 Property Types and Blob Property Support
 ----------------------------------------
 
+.. kernel-doc:: drivers/gpu/drm/drm_property.c
+   :doc: overview
+
 .. kernel-doc:: include/drm/drm_property.h
    :internal:
 

include/drm/drm_property.h

@@ -27,33 +27,192 @@
 #include <linux/ctype.h>
 #include <drm/drm_mode_object.h>
 
-struct drm_property_blob {
-	struct drm_mode_object base;
-	struct drm_device *dev;
-	struct list_head head_global;
-	struct list_head head_file;
-	size_t length;
-	unsigned char data[];
-};
-
+/**
+ * struct drm_property_enum - symbolic values for enumerations
+ * @value: numeric property value for this enum entry
+ * @head: list of enum values, linked to enum_list in &drm_property
+ * @name: symbolic name for the enum
+ *
+ * For enumeration and bitmask properties this structure stores the symbolic
+ * decoding for each value. This is used for example for the rotation property.
+ */
 struct drm_property_enum {
 	uint64_t value;
 	struct list_head head;
 	char name[DRM_PROP_NAME_LEN];
 };
 
+/**
+ * struct drm_property - modeset object property
+ *
+ * This structure represent a modeset object property. It combines both the name
+ * of the property with the set of permissible values. This means that when a
+ * driver wants to use a property with the same name on different objects, but
+ * with different value ranges, then it must create property for each one. An
+ * example would be rotation of &drm_plane, when e.g. the primary plane cannot
+ * be rotated. But if both the name and the value range match, then the same
+ * property structure can be instantiated multiple times for the same object.
+ * Userspace must be able to cope with this and cannot assume that the same
+ * symbolic property will have the same modeset object ID on all modeset
+ * objects.
+ *
+ * Properties are created by one of the special functions, as explained in
+ * detail in the @flags structure member.
+ *
+ * To actually expose a property it must be attached to each object using
+ * drm_object_attach_property(). Currently properties can only be attached to
+ * &drm_connector, &drm_crtc and &drm_plane.
+ *
+ * Properties are also used as the generic metadatatransport for the atomic
+ * IOCTL. Everything that was set directly in structures in the legacy modeset
+ * IOCTLs (like the plane source or destination windows, or e.g. the links to
+ * the CRTC) is exposed as a property with the DRM_MODE_PROP_ATOMIC flag set.
+ */
 struct drm_property {
+	/**
+	 * @head: per-device list of properties, for cleanup.
+	 */
 	struct list_head head;
+
+	/**
+	 * @base: base KMS object
+	 */
 	struct drm_mode_object base;
+
+	/**
+	 * @flags:
+	 *
+	 * Property flags and type. A property needs to be one of the following
+	 * types:
+	 *
+	 * DRM_MODE_PROP_RANGE
+	 *     Range properties report their minimum and maximum admissible unsigned values.
+	 *     The KMS core verifies that values set by application fit in that
+	 *     range. The range is unsigned. Range properties are created using
+	 *     drm_property_create_range().
+	 *
+	 * DRM_MODE_PROP_SIGNED_RANGE
+	 *     Range properties report their minimum and maximum admissible unsigned values.
+	 *     The KMS core verifies that values set by application fit in that
+	 *     range. The range is signed. Range properties are created using
+	 *     drm_property_create_signed_range().
+	 *
+	 * DRM_MODE_PROP_ENUM
+	 *     Enumerated properties take a numerical value that ranges from 0 to
+	 *     the number of enumerated values defined by the property minus one,
+	 *     and associate a free-formed string name to each value. Applications
+	 *     can retrieve the list of defined value-name pairs and use the
+	 *     numerical value to get and set property instance values. Enum
+	 *     properties are created using drm_property_create_enum().
+	 *
+	 * DRM_MODE_PROP_BITMASK
+	 *     Bitmask properties are enumeration properties that additionally
+	 *     restrict all enumerated values to the 0..63 range. Bitmask property
+	 *     instance values combine one or more of the enumerated bits defined
+	 *     by the property. Bitmask properties are created using
+	 *     drm_property_create_bitmask().
+	 *
+	 * DRM_MODE_PROB_OBJECT
+	 *     Object properties are used to link modeset objects. This is used
+	 *     extensively in the atomic support to create the display pipeline,
+	 *     by linking &drm_framebuffer to &drm_plane, &drm_plane to
+	 *     &drm_crtc and &drm_connector to &drm_crtc. An object property can
+	 *     only link to a specific type of &drm_mode_object, this limit is
+	 *     enforced by the core. Object properties are created using
+	 *     drm_property_create_object().
+	 *
+	 *     Object properties work like blob properties, but in a more
+	 *     general fashion. They are limited to atomic drivers and must have
+	 *     the DRM_MODE_PROP_ATOMIC flag set.
+	 *
+	 * DRM_MODE_PROP_BLOB
+	 *     Blob properties store a binary blob without any format restriction.
+	 *     The binary blobs are created as KMS standalone objects, and blob
+	 *     property instance values store the ID of their associated blob
+	 *     object. Blob properties are created by calling
+	 *     drm_property_create() with DRM_MODE_PROP_BLOB as the type.
+	 *
+	 *     Actual blob objects to contain blob data are created using
+	 *     drm_property_create_blob(), or through the corresponding IOCTL.
+	 *
+	 *     Besides the built-in limit to only accept blob objects blob
+	 *     properties work exactly like object properties. The only reasons
+	 *     blob properties exist is backwards compatibility with existing
+	 *     userspace.
+	 *
+	 * In addition a property can have any combination of the below flags:
+	 *
+	 * DRM_MODE_PROP_ATOMIC
+	 *     Set for properties which encode atomic modeset state. Such
+	 *     properties are not exposed to legacy userspace.
+	 *
+	 * DRM_MODE_PROP_IMMUTABLE
+	 *     Set for properties where userspace cannot be changed by
+	 *     userspace. The kernel is allowed to update the value of these
+	 *     properties. This is generally used to expose probe state to
+	 *     usersapce, e.g. the EDID, or the connector path property on DP
+	 *     MST sinks.
+	 */
 	uint32_t flags;
+
+	/**
+	 * @name: symbolic name of the properties
+	 */
 	char name[DRM_PROP_NAME_LEN];
+
+	/**
+	 * @num_values: size of the @values array.
+	 */
 	uint32_t num_values;
+
+	/**
+	 * @values:
+	 *
+	 * Array with limits and values for the property. The
+	 * interpretation of these limits is dependent upon the type per @flags.
+	 */
 	uint64_t *values;
+
+	/**
+	 * @dev: DRM device
+	 */
 	struct drm_device *dev;
 
+	/**
+	 * @enum_list:
+	 *
+	 * List of &drm_prop_enum_list structures with the symbolic names for
+	 * enum and bitmask values.
+	 */
 	struct list_head enum_list;
 };
 
+/**
+ * struct drm_property_blob - Blob data for &drm_property
+ * @base: base KMS object
+ * @dev: DRM device
+ * @head_global: entry on the global blob list in &drm_mode_config
+ *	property_blob_list.
+ * @head_file: entry on the per-file blob list in &drm_file blobs list.
+ * @length: size of the blob in bytes, invariant over the lifetime of the object
+ * @data: actual data, embedded at the end of this structure
+ *
+ * Blobs are used to store bigger values than what fits directly into the 64
+ * bits available for a &drm_property.
+ *
+ * Blobs are reference counted using drm_property_reference_blob() and
+ * drm_property_unreference_blob(). They are created using
+ * drm_property_create_blob().
+ */
+struct drm_property_blob {
+	struct drm_mode_object base;
+	struct drm_device *dev;
+	struct list_head head_global;
+	struct list_head head_file;
+	size_t length;
+	unsigned char data[];
+};
+
 struct drm_prop_enum_list {
 	int type;
 	char *name;
@@ -61,8 +220,16 @@ struct drm_prop_enum_list {
 
 #define obj_to_property(x) container_of(x, struct drm_property, base)
 
+/**
+ * drm_property_type_is - check the type of a property
+ * @property: property to check
+ * @type: property type to compare with
+ *
+ * This is a helper function becauase the uapi encoding of property types is
+ * a bit special for historical reasons.
+ */
 static inline bool drm_property_type_is(struct drm_property *property,
-		uint32_t type)
+					uint32_t type)
 {
 	/* instanceof for props.. handles extended type vs original types: */
 	if (property->flags & DRM_MODE_PROP_EXTENDED_TYPE)
@@ -109,8 +276,15 @@ int drm_property_replace_global_blob(struct drm_device *dev,
 struct drm_property_blob *drm_property_reference_blob(struct drm_property_blob *blob);
 void drm_property_unreference_blob(struct drm_property_blob *blob);
 
+/**
+ * drm_connector_find - find property object
+ * @dev: DRM device
+ * @id: property object id
+ *
+ * This function looks up the property object specified by id and returns it.
+ */
 static inline struct drm_property *drm_property_find(struct drm_device *dev,
-		uint32_t id)
+						     uint32_t id)
 {
 	struct drm_mode_object *mo;
 	mo = drm_mode_object_find(dev, id, DRM_MODE_OBJECT_PROPERTY);