Commit da024fe5 authored by Daniel Vetter's avatar Daniel Vetter
Browse files

drm/bridge: Improve kerneldoc 



Especially document the assumptions and semantics of the callbacks
carefully. Just a warm-up excercise really.

v2: Spelling fixes (Eric).

v3: Consolidate more with existing docs:

- Remove the overview section explaining the bridge funcs, that's
  now all in the drm_bridge_funcs kerneldoc in much more detail.

- Use & to reference structs so that kerneldoc automatically inserts
  hyperlinks.

v4: Review from Thierry.

Cc: Eric Anholt <eric@anholt.net>
Cc: Archit Taneja <architt@codeaurora.org>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Archit Taneja <architt@codeaurora.org> (v3)
Link: http://patchwork.freedesktop.org/patch/msgid/1449218769-16577-7-git-send-email-daniel.vetter@ffwll.ch


Reviewed-by: default avatarThierry Reding <treding@nvidia.com>
parent 2be94971

drivers/gpu/drm/drm_bridge.c

+26 −43
Original line number Diff line number Diff line
@@ -31,11 +31,11 @@ 
/**

 * 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

 * struct &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

 * A bridge is always attached 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
@@ -46,11 +46,16 @@ 
 * 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.

 * 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.

 * CRTCs, encoders or connectors and hence are not visible to userspace. They

 * just provide additional hooks to get the desired output at the end of the

 * encoder chain.

 *

 * Bridges can also be chained up using the next pointer in struct &drm_bridge.

 *

 * Both legacy CRTC helpers and the new atomic modeset helpers support bridges.

 */



static DEFINE_MUTEX(bridge_lock);
@@ -122,34 +127,12 @@ 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

 * 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.

 * For detailed specification of the bridge callbacks see &drm_bridge_funcs.

 */



/**
@@ -159,7 +142,7 @@ EXPORT_SYMBOL(drm_bridge_attach); 
 * @mode: desired mode to be set for the bridge

 * @adjusted_mode: updated mode that works for this bridge

 *

 * Calls 'mode_fixup' drm_bridge_funcs op for all the bridges in the

 * Calls ->mode_fixup() &drm_bridge_funcs op for all the bridges in the

 * encoder chain, starting from the first bridge to the last.

 *

 * Note: the bridge passed should be the one closest to the encoder
@@ -186,11 +169,11 @@ bool drm_bridge_mode_fixup(struct drm_bridge *bridge, 
EXPORT_SYMBOL(drm_bridge_mode_fixup);



/**

 * drm_bridge_disable - calls 'disable' drm_bridge_funcs op for all

 * drm_bridge_disable - calls ->disable() &drm_bridge_funcs op for all

 *			bridges in the encoder chain.

 * @bridge: bridge control structure

 *

 * Calls 'disable' drm_bridge_funcs op for all the bridges in the encoder

 * Calls ->disable() &drm_bridge_funcs op for all the bridges in the encoder

 * chain, starting from the last bridge to the first. These are called before

 * calling the encoder's prepare op.

 *
@@ -208,11 +191,11 @@ void drm_bridge_disable(struct drm_bridge *bridge) 
EXPORT_SYMBOL(drm_bridge_disable);



/**

 * drm_bridge_post_disable - calls 'post_disable' drm_bridge_funcs op for

 * drm_bridge_post_disable - calls ->post_disable() &drm_bridge_funcs op for

 *			     all bridges in the encoder chain.

 * @bridge: bridge control structure

 *

 * Calls 'post_disable' drm_bridge_funcs op for all the bridges in the

 * Calls ->post_disable() &drm_bridge_funcs op for all the bridges in the

 * encoder chain, starting from the first bridge to the last. These are called

 * after completing the encoder's prepare op.

 *
@@ -236,7 +219,7 @@ EXPORT_SYMBOL(drm_bridge_post_disable); 
 * @mode: desired mode to be set for the bridge

 * @adjusted_mode: updated mode that works for this bridge

 *

 * Calls 'mode_set' drm_bridge_funcs op for all the bridges in the

 * Calls ->mode_set() &drm_bridge_funcs op for all the bridges in the

 * encoder chain, starting from the first bridge to the last.

 *

 * Note: the bridge passed should be the one closest to the encoder
@@ -256,11 +239,11 @@ void drm_bridge_mode_set(struct drm_bridge *bridge, 
EXPORT_SYMBOL(drm_bridge_mode_set);



/**

 * drm_bridge_pre_enable - calls 'pre_enable' drm_bridge_funcs op for all

 * drm_bridge_pre_enable - calls ->pre_enable() &drm_bridge_funcs op for all

 *			   bridges in the encoder chain.

 * @bridge: bridge control structure

 *

 * Calls 'pre_enable' drm_bridge_funcs op for all the bridges in the encoder

 * Calls ->pre_enable() &drm_bridge_funcs op for all the bridges in the encoder

 * chain, starting from the last bridge to the first. These are called

 * before calling the encoder's commit op.

 *
@@ -278,11 +261,11 @@ void drm_bridge_pre_enable(struct drm_bridge *bridge) 
EXPORT_SYMBOL(drm_bridge_pre_enable);



/**

 * drm_bridge_enable - calls 'enable' drm_bridge_funcs op for all bridges

 * drm_bridge_enable - calls ->enable() &drm_bridge_funcs op for all bridges

 *		       in the encoder chain.

 * @bridge: bridge control structure

 *

 * Calls 'enable' drm_bridge_funcs op for all the bridges in the encoder

 * Calls ->enable() &drm_bridge_funcs op for all the bridges in the encoder

 * chain, starting from the first bridge to the last. These are called

 * after completing the encoder's commit op.

 *

include/drm/drm_crtc.h

+96 −6
Original line number Diff line number Diff line
@@ -883,24 +883,114 @@ struct drm_plane { 
/**

 * struct drm_bridge_funcs - drm_bridge control functions

 * @attach: Called during drm_bridge_attach

 * @mode_fixup: Try to fixup (or reject entirely) proposed mode for this bridge

 * @disable: Called right before encoder prepare, disables the bridge

 * @post_disable: Called right after encoder prepare, for lockstepped disable

 * @mode_set: Set this mode to the bridge

 * @pre_enable: Called right before encoder commit, for lockstepped commit

 * @enable: Called right after encoder commit, enables the bridge

 */

struct drm_bridge_funcs {

	int (*attach)(struct drm_bridge *bridge);



	/**

	 * @mode_fixup:

	 *

	 * This callback is used to validate and adjust a mode. The paramater

	 * mode is the display mode that should be fed to the next element in

	 * the display chain, either the final &drm_connector or the next

	 * &drm_bridge. The parameter adjusted_mode is the input mode the bridge

	 * requires. It can be modified by this callback and does not need to

	 * match mode.

	 *

	 * This is the only hook that allows a bridge to reject a modeset. If

	 * this function passes all other callbacks must succeed for this

	 * configuration.

	 *

	 * NOTE:

	 *

	 * This function is called in the check phase of atomic modesets, which

	 * can be aborted for any reason (including on userspace's request to

	 * just check whether a configuration would be possible). Drivers MUST

	 * NOT touch any persistent state (hardware or software) or data

	 * structures except the passed in adjusted_mode parameter.

	 *

	 * RETURNS:

	 *

	 * True if an acceptable configuration is possible, false if the modeset

	 * operation should be rejected.

	 */

	bool (*mode_fixup)(struct drm_bridge *bridge,

			   const struct drm_display_mode *mode,

			   struct drm_display_mode *adjusted_mode);

	/**

	 * @disable:

	 *

	 * This callback should disable the bridge. It is called right before

	 * the preceding element in the display pipe is disabled. If the

	 * preceding element is a bridge this means it's called before that

	 * bridge's ->disable() function. If the preceding element is a

	 * &drm_encoder it's called right before the encoder's ->disable(),

	 * ->prepare() or ->dpms() hook from struct &drm_encoder_helper_funcs.

	 *

	 * The bridge can assume that the display pipe (i.e. clocks and timing

	 * signals) feeding it is still running when this callback is called.

	 */

	void (*disable)(struct drm_bridge *bridge);



	/**

	 * @post_disable:

	 *

	 * This callback should disable the bridge. It is called right after

	 * the preceding element in the display pipe is disabled. If the

	 * preceding element is a bridge this means it's called after that

	 * bridge's ->post_disable() function. If the preceding element is a

	 * &drm_encoder it's called right after the encoder's ->disable(),

	 * ->prepare() or ->dpms() hook from struct &drm_encoder_helper_funcs.

	 *

	 * The bridge must assume that the display pipe (i.e. clocks and timing

	 * singals) feeding it is no longer running when this callback is

	 * called.

	 */

	void (*post_disable)(struct drm_bridge *bridge);



	/**

	 * @mode_set:

	 *

	 * This callback should set the given mode on the bridge. It is called

	 * after the ->mode_set() callback for the preceding element in the

	 * display pipeline has been called already. The display pipe (i.e.

	 * clocks and timing signals) is off when this function is called.

	 */

	void (*mode_set)(struct drm_bridge *bridge,

			 struct drm_display_mode *mode,

			 struct drm_display_mode *adjusted_mode);

	/**

	 * @pre_enable:

	 *

	 * This callback should enable the bridge. It is called right before

	 * the preceding element in the display pipe is enabled. If the

	 * preceding element is a bridge this means it's called before that

	 * bridge's ->pre_enable() function. If the preceding element is a

	 * &drm_encoder it's called right before the encoder's ->enable(),

	 * ->commit() or ->dpms() hook from struct &drm_encoder_helper_funcs.

	 *

	 * The display pipe (i.e. clocks and timing signals) feeding this bridge

	 * will not yet be running when this callback is called. The bridge must

	 * not enable the display link feeding the next bridge in the chain (if

	 * there is one) when this callback is called.

	 */

	void (*pre_enable)(struct drm_bridge *bridge);



	/**

	 * @enable:

	 *

	 * This callback should enable the bridge. It is called right after

	 * the preceding element in the display pipe is enabled. If the

	 * preceding element is a bridge this means it's called after that

	 * bridge's ->enable() function. If the preceding element is a

	 * &drm_encoder it's called right after the encoder's ->enable(),

	 * ->commit() or ->dpms() hook from struct &drm_encoder_helper_funcs.

	 *

	 * The bridge can assume that the display pipe (i.e. clocks and timing

	 * signals) feeding it is running when this callback is called. This

	 * callback must enable the display link feeding the next bridge in the

	 * chain if there is one.

	 */

	void (*enable)(struct drm_bridge *bridge);

};

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