Re: [PATCH 06/28] drm/bridge: Improve kerneldoc

Archit Taneja
2015-12-04T10:43:25Z

On 12/04/2015 02:15 PM, Daniel Vetter wrote:
> 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.

Reviewed-by: Archit Taneja <architt@codeaurora.org>

>
> Cc: Eric Anholt <eric@anholt.net>
> Cc: Archit Taneja <architt@codeaurora.org>
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
> drivers/gpu/drm/drm_bridge.c | 69 +++++++++++------------------
> include/drm/drm_crtc.h | 102 ++++++++++++++++++++++++++++++++++++++++---
> 2 files changed, 122 insertions(+), 49 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index 6b8f7211e543..26dd1cfb6078 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -31,14 +31,14 @@
> /**
> * 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 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
> + * encoder ---> bridge B ---> bridge A
> *
> * Here, the output of the encoder feeds to bridge B, and that furthers feeds to
> * 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.
> *
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index e8f8e4e9a6a1..ec3632e62b3f 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -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 ->disaable 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_disaable 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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