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

[Daniel Vetter]

On Thu, May 21, 2015 at 10:03:38AM +0200, Daniel Vetter wrote:
> 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 at 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 at ffwll.ch>

Hm somehow thought Thierry maintains drm_bridge, but he's doing drm_panel.
Hence done these two small changes and applied both patches to
topic/drm-misc.
-Daniel

> 
> > + *
> > + * 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

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