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authorArchit Taneja <architt@codeaurora.org>2015-05-21 07:33:17 +0200
committerDaniel Vetter <daniel.vetter@ffwll.ch>2015-05-21 13:56:51 +0200
commit2331b4e476e0dc705825c8f5462fa1274b6d3b97 (patch)
tree951128604c487308f99b66f08f855078465b29e7 /drivers/gpu/drm/drm_bridge.c
parentdrm: bridge: Allow daisy chaining of bridges (diff)
downloadlinux-2331b4e476e0dc705825c8f5462fa1274b6d3b97.tar.xz
linux-2331b4e476e0dc705825c8f5462fa1274b6d3b97.zip
drm/DocBook: Add more drm_bridge documentation
Add DOC sections giving an overview of drm_bridge and how to fill up the drm_bridge_funcs ops. Add these to drm.tpml in DocBook. Add headerdocs for funcs in drm_bridge.c that don't have them yet. Signed-off-by: Archit Taneja <architt@codeaurora.org> [danvet: Amend kerneldoc as discussed with Archit.] Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Diffstat (limited to 'drivers/gpu/drm/drm_bridge.c')
-rw-r--r--drivers/gpu/drm/drm_bridge.c95
1 files changed, 95 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index c3a85ce5a7c4..6b8f7211e543 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -28,9 +28,42 @@
#include "drm/drmP.h"
+/**
+ * DOC: overview
+ *
+ * drm_bridge represents a device that hangs on to an encoder. These are handy
+ * when a regular drm_encoder entity isn't enough to represent the entire
+ * encoder chain.
+ *
+ * A bridge is always associated to a single drm_encoder at a time, but can be
+ * either connected to it directly, or through an intermediate bridge:
+ *
+ * encoder ---> bridge B ---> bridge A
+ *
+ * Here, the output of the encoder feeds to bridge B, and that furthers feeds to
+ * bridge A.
+ *
+ * The driver using the bridge is responsible to make the associations between
+ * the encoder and bridges. Once these links are made, the bridges will
+ * participate along with encoder functions to perform mode_set/enable/disable
+ * through the ops provided in drm_bridge_funcs.
+ *
+ * drm_bridge, like drm_panel, aren't drm_mode_object entities like planes,
+ * crtcs, encoders or connectors. They just provide additional hooks to get the
+ * desired output at the end of the encoder chain.
+ */
+
static DEFINE_MUTEX(bridge_lock);
static LIST_HEAD(bridge_list);
+/**
+ * drm_bridge_add - add the given bridge to the global bridge list
+ *
+ * @bridge: bridge control structure
+ *
+ * RETURNS:
+ * Unconditionally returns Zero.
+ */
int drm_bridge_add(struct drm_bridge *bridge)
{
mutex_lock(&bridge_lock);
@@ -41,6 +74,11 @@ int drm_bridge_add(struct drm_bridge *bridge)
}
EXPORT_SYMBOL(drm_bridge_add);
+/**
+ * drm_bridge_remove - remove the given bridge from the global bridge list
+ *
+ * @bridge: bridge control structure
+ */
void drm_bridge_remove(struct drm_bridge *bridge)
{
mutex_lock(&bridge_lock);
@@ -49,6 +87,21 @@ void drm_bridge_remove(struct drm_bridge *bridge)
}
EXPORT_SYMBOL(drm_bridge_remove);
+/**
+ * drm_bridge_attach - associate given bridge to our DRM device
+ *
+ * @dev: DRM device
+ * @bridge: bridge control structure
+ *
+ * called by a kms driver to link one of our encoder/bridge to the given
+ * bridge.
+ *
+ * Note that setting up links between the bridge and our encoder/bridge
+ * objects needs to be handled by the kms driver itself
+ *
+ * RETURNS:
+ * Zero on success, error code on failure
+ */
int drm_bridge_attach(struct drm_device *dev, struct drm_bridge *bridge)
{
if (!dev || !bridge)
@@ -67,6 +120,39 @@ int drm_bridge_attach(struct drm_device *dev, struct drm_bridge *bridge)
EXPORT_SYMBOL(drm_bridge_attach);
/**
+ * DOC: bridge callbacks
+ *
+ * The drm_bridge_funcs ops are populated by the bridge driver. The drm
+ * internals(atomic and crtc helpers) use the helpers defined in drm_bridge.c
+ * These helpers call a specific drm_bridge_funcs op for all the bridges
+ * during encoder configuration.
+ *
+ * When creating a bridge driver, one can implement drm_bridge_funcs op with
+ * the help of these rough rules:
+ *
+ * pre_enable: this contains things needed to be done for the bridge before
+ * its clock and timings are enabled by its source. For a bridge, its source
+ * is generally the encoder or bridge just before it in the encoder chain.
+ *
+ * enable: this contains things needed to be done for the bridge once its
+ * source is enabled. In other words, enable is called once the source is
+ * ready with clock and timing needed by the bridge.
+ *
+ * disable: this contains things needed to be done for the bridge assuming
+ * that its source is still enabled, i.e. clock and timings are still on.
+ *
+ * post_disable: this contains things needed to be done for the bridge once
+ * its source is disabled, i.e. once clocks and timings are off.
+ *
+ * mode_fixup: this should fixup the given mode for the bridge. It is called
+ * after the encoder's mode fixup. mode_fixup can also reject a mode completely
+ * if it's unsuitable for the hardware.
+ *
+ * mode_set: this sets up the mode for the bridge. It assumes that its source
+ * (an encoder or a bridge) has set the mode too.
+ */
+
+/**
* drm_bridge_mode_fixup - fixup proposed mode for all bridges in the
* encoder chain
* @bridge: bridge control structure
@@ -214,6 +300,15 @@ void drm_bridge_enable(struct drm_bridge *bridge)
EXPORT_SYMBOL(drm_bridge_enable);
#ifdef CONFIG_OF
+/**
+ * of_drm_find_bridge - find the bridge corresponding to the device node in
+ * the global bridge list
+ *
+ * @np: device node
+ *
+ * RETURNS:
+ * drm_bridge control struct on success, NULL on failure
+ */
struct drm_bridge *of_drm_find_bridge(struct device_node *np)
{
struct drm_bridge *bridge;