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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: Daniel 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: Thierry Reding <treding@nvidia.com>
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Daniel Vetter
parent
2be94971c7
commit
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@ -31,14 +31,14 @@
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/**
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* DOC: overview
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*
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* drm_bridge represents a device that hangs on to an encoder. These are handy
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* when a regular drm_encoder entity isn't enough to represent the entire
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* struct &drm_bridge represents a device that hangs on to an encoder. These are
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* handy when a regular &drm_encoder entity isn't enough to represent the entire
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* encoder chain.
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*
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* A bridge is always associated to a single drm_encoder at a time, but can be
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* A bridge is always attached to a single &drm_encoder at a time, but can be
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* either connected to it directly, or through an intermediate bridge:
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*
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* encoder ---> bridge B ---> bridge A
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* encoder ---> bridge B ---> bridge A
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*
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* Here, the output of the encoder feeds to bridge B, and that furthers feeds to
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* bridge A.
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@ -46,11 +46,16 @@
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* The driver using the bridge is responsible to make the associations between
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* the encoder and bridges. Once these links are made, the bridges will
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* participate along with encoder functions to perform mode_set/enable/disable
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* through the ops provided in drm_bridge_funcs.
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* through the ops provided in &drm_bridge_funcs.
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*
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* drm_bridge, like drm_panel, aren't drm_mode_object entities like planes,
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* crtcs, encoders or connectors. They just provide additional hooks to get the
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* desired output at the end of the encoder chain.
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* CRTCs, encoders or connectors and hence are not visible to userspace. They
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* just provide additional hooks to get the desired output at the end of the
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* encoder chain.
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*
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* Bridges can also be chained up using the next pointer in struct &drm_bridge.
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*
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* Both legacy CRTC helpers and the new atomic modeset helpers support bridges.
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*/
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static DEFINE_MUTEX(bridge_lock);
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@ -122,34 +127,12 @@ EXPORT_SYMBOL(drm_bridge_attach);
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/**
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* DOC: bridge callbacks
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*
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* The drm_bridge_funcs ops are populated by the bridge driver. The drm
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* internals(atomic and crtc helpers) use the helpers defined in drm_bridge.c
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* These helpers call a specific drm_bridge_funcs op for all the bridges
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* The &drm_bridge_funcs ops are populated by the bridge driver. The DRM
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* internals (atomic and CRTC helpers) use the helpers defined in drm_bridge.c
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* These helpers call a specific &drm_bridge_funcs op for all the bridges
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* during encoder configuration.
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*
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* When creating a bridge driver, one can implement drm_bridge_funcs op with
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* the help of these rough rules:
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*
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* pre_enable: this contains things needed to be done for the bridge before
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* its clock and timings are enabled by its source. For a bridge, its source
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* is generally the encoder or bridge just before it in the encoder chain.
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*
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* enable: this contains things needed to be done for the bridge once its
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* source is enabled. In other words, enable is called once the source is
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* ready with clock and timing needed by the bridge.
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*
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* disable: this contains things needed to be done for the bridge assuming
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* that its source is still enabled, i.e. clock and timings are still on.
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*
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* post_disable: this contains things needed to be done for the bridge once
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* its source is disabled, i.e. once clocks and timings are off.
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*
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* mode_fixup: this should fixup the given mode for the bridge. It is called
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* after the encoder's mode fixup. mode_fixup can also reject a mode completely
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* if it's unsuitable for the hardware.
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*
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* mode_set: this sets up the mode for the bridge. It assumes that its source
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* (an encoder or a bridge) has set the mode too.
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* For detailed specification of the bridge callbacks see &drm_bridge_funcs.
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*/
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/**
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@ -159,7 +142,7 @@ EXPORT_SYMBOL(drm_bridge_attach);
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* @mode: desired mode to be set for the bridge
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* @adjusted_mode: updated mode that works for this bridge
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*
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* Calls 'mode_fixup' drm_bridge_funcs op for all the bridges in the
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* Calls ->mode_fixup() &drm_bridge_funcs op for all the bridges in the
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* encoder chain, starting from the first bridge to the last.
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*
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* Note: the bridge passed should be the one closest to the encoder
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@ -186,11 +169,11 @@ bool drm_bridge_mode_fixup(struct drm_bridge *bridge,
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EXPORT_SYMBOL(drm_bridge_mode_fixup);
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/**
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* drm_bridge_disable - calls 'disable' drm_bridge_funcs op for all
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* drm_bridge_disable - calls ->disable() &drm_bridge_funcs op for all
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* bridges in the encoder chain.
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* @bridge: bridge control structure
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*
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* Calls 'disable' drm_bridge_funcs op for all the bridges in the encoder
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* Calls ->disable() &drm_bridge_funcs op for all the bridges in the encoder
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* chain, starting from the last bridge to the first. These are called before
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* calling the encoder's prepare op.
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*
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@ -208,11 +191,11 @@ void drm_bridge_disable(struct drm_bridge *bridge)
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EXPORT_SYMBOL(drm_bridge_disable);
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/**
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* drm_bridge_post_disable - calls 'post_disable' drm_bridge_funcs op for
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* drm_bridge_post_disable - calls ->post_disable() &drm_bridge_funcs op for
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* all bridges in the encoder chain.
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* @bridge: bridge control structure
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*
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* Calls 'post_disable' drm_bridge_funcs op for all the bridges in the
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* Calls ->post_disable() &drm_bridge_funcs op for all the bridges in the
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* encoder chain, starting from the first bridge to the last. These are called
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* after completing the encoder's prepare op.
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*
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@ -236,7 +219,7 @@ EXPORT_SYMBOL(drm_bridge_post_disable);
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* @mode: desired mode to be set for the bridge
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* @adjusted_mode: updated mode that works for this bridge
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*
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* Calls 'mode_set' drm_bridge_funcs op for all the bridges in the
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* Calls ->mode_set() &drm_bridge_funcs op for all the bridges in the
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* encoder chain, starting from the first bridge to the last.
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*
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* Note: the bridge passed should be the one closest to the encoder
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@ -256,11 +239,11 @@ void drm_bridge_mode_set(struct drm_bridge *bridge,
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EXPORT_SYMBOL(drm_bridge_mode_set);
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/**
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* drm_bridge_pre_enable - calls 'pre_enable' drm_bridge_funcs op for all
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* drm_bridge_pre_enable - calls ->pre_enable() &drm_bridge_funcs op for all
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* bridges in the encoder chain.
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* @bridge: bridge control structure
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*
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* Calls 'pre_enable' drm_bridge_funcs op for all the bridges in the encoder
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* Calls ->pre_enable() &drm_bridge_funcs op for all the bridges in the encoder
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* chain, starting from the last bridge to the first. These are called
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* before calling the encoder's commit op.
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*
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@ -278,11 +261,11 @@ void drm_bridge_pre_enable(struct drm_bridge *bridge)
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EXPORT_SYMBOL(drm_bridge_pre_enable);
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/**
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* drm_bridge_enable - calls 'enable' drm_bridge_funcs op for all bridges
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* drm_bridge_enable - calls ->enable() &drm_bridge_funcs op for all bridges
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* in the encoder chain.
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* @bridge: bridge control structure
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*
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* Calls 'enable' drm_bridge_funcs op for all the bridges in the encoder
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* Calls ->enable() &drm_bridge_funcs op for all the bridges in the encoder
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* chain, starting from the first bridge to the last. These are called
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* after completing the encoder's commit op.
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*
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@ -883,24 +883,114 @@ struct drm_plane {
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/**
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* struct drm_bridge_funcs - drm_bridge control functions
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* @attach: Called during drm_bridge_attach
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* @mode_fixup: Try to fixup (or reject entirely) proposed mode for this bridge
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* @disable: Called right before encoder prepare, disables the bridge
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* @post_disable: Called right after encoder prepare, for lockstepped disable
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* @mode_set: Set this mode to the bridge
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* @pre_enable: Called right before encoder commit, for lockstepped commit
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* @enable: Called right after encoder commit, enables the bridge
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*/
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struct drm_bridge_funcs {
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int (*attach)(struct drm_bridge *bridge);
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/**
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* @mode_fixup:
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*
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* This callback is used to validate and adjust a mode. The paramater
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* mode is the display mode that should be fed to the next element in
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* the display chain, either the final &drm_connector or the next
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* &drm_bridge. The parameter adjusted_mode is the input mode the bridge
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* requires. It can be modified by this callback and does not need to
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* match mode.
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*
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* This is the only hook that allows a bridge to reject a modeset. If
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* this function passes all other callbacks must succeed for this
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* configuration.
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*
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* NOTE:
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*
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* This function is called in the check phase of atomic modesets, which
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* can be aborted for any reason (including on userspace's request to
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* just check whether a configuration would be possible). Drivers MUST
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* NOT touch any persistent state (hardware or software) or data
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* structures except the passed in adjusted_mode parameter.
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*
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* RETURNS:
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*
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* True if an acceptable configuration is possible, false if the modeset
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* operation should be rejected.
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*/
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bool (*mode_fixup)(struct drm_bridge *bridge,
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const struct drm_display_mode *mode,
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struct drm_display_mode *adjusted_mode);
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/**
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* @disable:
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*
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* This callback should disable the bridge. It is called right before
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* the preceding element in the display pipe is disabled. If the
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* preceding element is a bridge this means it's called before that
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* bridge's ->disable() function. If the preceding element is a
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* &drm_encoder it's called right before the encoder's ->disable(),
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* ->prepare() or ->dpms() hook from struct &drm_encoder_helper_funcs.
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*
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* The bridge can assume that the display pipe (i.e. clocks and timing
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* signals) feeding it is still running when this callback is called.
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*/
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void (*disable)(struct drm_bridge *bridge);
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/**
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* @post_disable:
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*
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* This callback should disable the bridge. It is called right after
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* the preceding element in the display pipe is disabled. If the
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* preceding element is a bridge this means it's called after that
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* bridge's ->post_disable() function. If the preceding element is a
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* &drm_encoder it's called right after the encoder's ->disable(),
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* ->prepare() or ->dpms() hook from struct &drm_encoder_helper_funcs.
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*
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* The bridge must assume that the display pipe (i.e. clocks and timing
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* singals) feeding it is no longer running when this callback is
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* called.
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*/
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void (*post_disable)(struct drm_bridge *bridge);
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/**
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* @mode_set:
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*
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* This callback should set the given mode on the bridge. It is called
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* after the ->mode_set() callback for the preceding element in the
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* display pipeline has been called already. The display pipe (i.e.
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* clocks and timing signals) is off when this function is called.
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*/
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void (*mode_set)(struct drm_bridge *bridge,
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struct drm_display_mode *mode,
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struct drm_display_mode *adjusted_mode);
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/**
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* @pre_enable:
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*
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* This callback should enable the bridge. It is called right before
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* the preceding element in the display pipe is enabled. If the
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* preceding element is a bridge this means it's called before that
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* bridge's ->pre_enable() function. If the preceding element is a
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* &drm_encoder it's called right before the encoder's ->enable(),
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* ->commit() or ->dpms() hook from struct &drm_encoder_helper_funcs.
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*
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* The display pipe (i.e. clocks and timing signals) feeding this bridge
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* will not yet be running when this callback is called. The bridge must
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* not enable the display link feeding the next bridge in the chain (if
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* there is one) when this callback is called.
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*/
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void (*pre_enable)(struct drm_bridge *bridge);
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/**
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* @enable:
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*
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* This callback should enable the bridge. It is called right after
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* the preceding element in the display pipe is enabled. If the
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* preceding element is a bridge this means it's called after that
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* bridge's ->enable() function. If the preceding element is a
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* &drm_encoder it's called right after the encoder's ->enable(),
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* ->commit() or ->dpms() hook from struct &drm_encoder_helper_funcs.
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*
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* The bridge can assume that the display pipe (i.e. clocks and timing
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* signals) feeding it is running when this callback is called. This
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* callback must enable the display link feeding the next bridge in the
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* chain if there is one.
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*/
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void (*enable)(struct drm_bridge *bridge);
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};
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