drm/doc: Document the KMS property API

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 143 insertions, 0 deletions

diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
index cea420dc712d..4d54ac8b2032 100644
--- a/Documentation/DocBook/drm.tmpl
+++ b/Documentation/DocBook/drm.tmpl
@@ -1236,6 +1236,15 @@ int max_width, max_height;</synopsis>
           <title>Miscellaneous</title>
           <itemizedlist>
             <listitem>
+              <synopsis>void (*set_property)(struct drm_crtc *crtc,
+                     struct drm_property *property, uint64_t value);</synopsis>
+              <para>
+                Set the value of the given CRTC property to
+                <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
+                for more information about properties.
+              </para>
+            </listitem>
+            <listitem>
               <synopsis>void (*gamma_set)(struct drm_crtc *crtc, u16 *r, u16 *g, u16 *b,
                         uint32_t start, uint32_t size);</synopsis>
               <para>
@@ -1385,6 +1394,15 @@ int max_width, max_height;</synopsis>
               <xref linkend="drm-kms-init"/>.
             </para>
           </listitem>
+          <listitem>
+            <synopsis>void (*set_property)(struct drm_plane *plane,
+                     struct drm_property *property, uint64_t value);</synopsis>
+            <para>
+              Set the value of the given plane property to
+              <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
+              for more information about properties.
+            </para>
+          </listitem>
         </itemizedlist>
       </sect3>
     </sect2>
@@ -1594,6 +1612,15 @@ int max_width, max_height;</synopsis>
           <title>Miscellaneous</title>
           <itemizedlist>
             <listitem>
+              <synopsis>void (*set_property)(struct drm_connector *connector,
+                     struct drm_property *property, uint64_t value);</synopsis>
+              <para>
+                Set the value of the given connector property to
+                <parameter>value</parameter>. See <xref linkend="drm-kms-properties"/>
+                for more information about properties.
+              </para>
+            </listitem>
+            <listitem>
               <synopsis>void (*destroy)(struct drm_connector *connector);</synopsis>
               <para>
                 Destroy the connector when not needed anymore. See
@@ -2187,6 +2214,122 @@ void intel_crt_init(struct drm_device *dev)
     </sect2>
   </sect1>
 
+  <!-- Internals: kms properties -->
+
+  <sect1 id="drm-kms-properties">
+    <title>KMS Properties</title>
+    <para>
+      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.
+    </para>
+    <para>
+      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.
+    </para>
+    <para>
+      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 propery
+      and shared between all instances of the property.
+    </para>
+    <para>
+      Every property is created with a type that influences how the KMS core
+      handles the property. Supported property types are
+      <variablelist>
+        <varlistentry>
+          <term>DRM_MODE_PROP_RANGE</term>
+          <listitem><para>Range properties report their minimum and maximum
+            admissible values. The KMS core verifies that values set by
+            application fit in that range.</para></listitem>
+        </varlistentry>
+        <varlistentry>
+          <term>DRM_MODE_PROP_ENUM</term>
+          <listitem><para>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.
+            </para></listitem>
+        </varlistentry>
+        <varlistentry>
+          <term>DRM_MODE_PROP_BITMASK</term>
+          <listitem><para>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.</para></listitem>
+        </varlistentry>
+        <varlistentry>
+          <term>DRM_MODE_PROP_BLOB</term>
+          <listitem><para>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.</para>
+            <para>Blob properties are only used for the connector EDID property
+            and cannot be created by drivers.</para></listitem>
+        </varlistentry>
+      </variablelist>
+    </para>
+    <para>
+      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.
+      <itemizedlist>
+        <listitem>
+          <synopsis>struct drm_property *drm_property_create_range(struct drm_device *dev, int flags,
+                                               const char *name,
+                                               uint64_t min, uint64_t max);</synopsis>
+          <para>Create a range property with the given minimum and maximum
+            values.</para>
+        </listitem>
+        <listitem>
+          <synopsis>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);</synopsis>
+          <para>Create an enumerated property. The <parameter>props</parameter>
+            argument points to an array of <parameter>num_values</parameter>
+            value-name pairs.</para>
+        </listitem>
+        <listitem>
+          <synopsis>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);</synopsis>
+          <para>Create a bitmask property. The <parameter>props</parameter>
+            argument points to an array of <parameter>num_values</parameter>
+            value-name pairs.</para>
+        </listitem>
+      </itemizedlist>
+    </para>
+    <para>
+      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.
+    </para>
+    <para>
+      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 <function>drm_property_create</function> function
+      and manually add enumeration value-name pairs by calling the
+      <function>drm_property_add_enum</function> function. Care must be taken to
+      properly specify the property type through the <parameter>flags</parameter>
+      argument.
+    </para>
+    <para>
+      After creating properties drivers can attach property instances to CRTC,
+      connector and plane objects by calling the
+      <function>drm_object_attach_property</function>. The function takes a
+      pointer to the target object, a pointer to the previously created property
+      and an initial instance value.
+    </para>
+  </sect1>
+
   <!-- Internals: vertical blanking -->
 
   <sect1 id="drm-vertical-blank">