Re: [PATCH v4 2/2] drm/DocBook: Add more drm_bridge documentation

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, May 21, 2015 at 11:03:17AM +0530, Archit Taneja wrote:
> 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>
> ---
>  Documentation/DocBook/drm.tmpl | 12 ++++++
>  drivers/gpu/drm/drm_bridge.c   | 94 ++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 106 insertions(+)
> 
> diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl
> index 9765a4c..1dc0f45 100644
> --- a/Documentation/DocBook/drm.tmpl
> +++ b/Documentation/DocBook/drm.tmpl
> @@ -2439,6 +2439,18 @@ void intel_crt_init(struct drm_device *dev)
>  	  <title>Tile group</title>
>  !Pdrivers/gpu/drm/drm_crtc.c Tile group
>      </sect2>
> +    <sect2>
> +	<title>Bridges</title>
> +      <sect3>
> +	 <title>Overview</title>
> +!Pdrivers/gpu/drm/drm_bridge.c overview
> +      </sect3>
> +      <sect3>
> +	 <title>Default bridge callback sequence</title>
> +!Pdrivers/gpu/drm/drm_bridge.c bridge callbacks
> +      </sect3>
> +!Edrivers/gpu/drm/drm_bridge.c
> +    </sect2>
>    </sect1>
>  
>    <!-- Internals: kms properties -->
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index c3a85ce..a7c4e10 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 +120,38 @@ 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 needs to be done for the bridge once its

s/needs/needed/

> + * 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.

Maybe add "mode_fixup can also reject a mode completely if it's unsuitable
for the hardware."

With that for the series: Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> + *
> + * 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 +299,15 @@ 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;
> -- 
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> hosted by The Linux Foundation
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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