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resource.c

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  • drm_bridge.h 36.14 KiB
    /*
     * Copyright (c) 2016 Intel Corporation
     *
     * Permission to use, copy, modify, distribute, and sell this software and its
     * documentation for any purpose is hereby granted without fee, provided that
     * the above copyright notice appear in all copies and that both that copyright
     * notice and this permission notice appear in supporting documentation, and
     * that the name of the copyright holders not be used in advertising or
     * publicity pertaining to distribution of the software without specific,
     * written prior permission.  The copyright holders make no representations
     * about the suitability of this software for any purpose.  It is provided "as
     * is" without express or implied warranty.
     *
     * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
     * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
     * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
     * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
     * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
     * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
     * OF THIS SOFTWARE.
     */
    
    #ifndef __DRM_BRIDGE_H__
    #define __DRM_BRIDGE_H__
    
    #include <linux/ctype.h>
    #include <linux/list.h>
    #include <linux/mutex.h>
    
    #include <drm/drm_atomic.h>
    #include <drm/drm_encoder.h>
    #include <drm/drm_mode_object.h>
    #include <drm/drm_modes.h>
    
    struct device_node;
    
    struct drm_bridge;
    struct drm_bridge_timings;
    struct drm_connector;
    struct drm_display_info;
    struct drm_minor;
    struct drm_panel;
    struct edid;
    struct i2c_adapter;
    
    /**
     * enum drm_bridge_attach_flags - Flags for &drm_bridge_funcs.attach
     */
    enum drm_bridge_attach_flags {
    	/**
    	 * @DRM_BRIDGE_ATTACH_NO_CONNECTOR: When this flag is set the bridge
    	 * shall not create a drm_connector.
    	 */
    	DRM_BRIDGE_ATTACH_NO_CONNECTOR = BIT(0),
    };
    
    /**
     * struct drm_bridge_funcs - drm_bridge control functions
     */
    struct drm_bridge_funcs {
    	/**
    	 * @attach:
    	 *
    	 * This callback is invoked whenever our bridge is being attached to a
    	 * &drm_encoder. The flags argument tunes the behaviour of the attach
    	 * operation (see DRM_BRIDGE_ATTACH_*).
    	 *
    	 * The @attach callback is optional.
    	 *
    	 * RETURNS:
    	 *
    	 * Zero on success, error code on failure.
    	 */
    	int (*attach)(struct drm_bridge *bridge,
    		      enum drm_bridge_attach_flags flags);
    
    	/**
    	 * @detach:
    	 *
    	 * This callback is invoked whenever our bridge is being detached from a
    	 * &drm_encoder.
    	 *
    	 * The @detach callback is optional.
    	 */
    	void (*detach)(struct drm_bridge *bridge);
    
    	/**
    	 * @mode_valid:
    	 *
    	 * This callback is used to check if a specific mode is valid in this
    	 * bridge. This should be implemented if the bridge has some sort of
    	 * restriction in the modes it can display. For example, a given bridge
    	 * may be responsible to set a clock value. If the clock can not
    	 * produce all the values for the available modes then this callback
    	 * can be used to restrict the number of modes to only the ones that
    	 * can be displayed.
    	 *
    	 * This hook is used by the probe helpers to filter the mode list in
    	 * drm_helper_probe_single_connector_modes(), and it is used by the
    	 * atomic helpers to validate modes supplied by userspace in
    	 * drm_atomic_helper_check_modeset().
    	 *
    	 * The @mode_valid callback is optional.
    	 *
    	 * NOTE:
    	 *
    	 * Since this function is both called from the check phase of an atomic
    	 * commit, and the mode validation in the probe paths it is not allowed
    	 * to look at anything else but the passed-in mode, and validate it
    	 * against configuration-invariant hardware constraints. Any further
    	 * limits which depend upon the configuration can only be checked in
    	 * @mode_fixup.
    	 *
    	 * RETURNS:
    	 *
    	 * drm_mode_status Enum
    	 */
    	enum drm_mode_status (*mode_valid)(struct drm_bridge *bridge,
    					   const struct drm_display_info *info,
    					   const struct drm_display_mode *mode);
    
    	/**
    	 * @mode_fixup:
    	 *
    	 * This callback is used to validate and adjust a mode. The parameter
    	 * 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. See also &drm_crtc_state.adjusted_mode for more details.
    	 *
    	 * 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.
    	 *
    	 * The mode_fixup callback is optional. &drm_bridge_funcs.mode_fixup()
    	 * is not called when &drm_bridge_funcs.atomic_check() is implemented,
    	 * so only one of them should be provided.
    	 *
    	 * 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 @state parameter.
    	 *
    	 * Also beware that userspace can request its own custom modes, neither
    	 * core nor helpers filter modes to the list of probe modes reported by
    	 * the GETCONNECTOR IOCTL and stored in &drm_connector.modes. To ensure
    	 * that modes are filtered consistently put any bridge constraints and
    	 * limits checks into @mode_valid.
    	 *
    	 * 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 vfunc. If the preceding element is a &drm_encoder
    	 * it's called right before the &drm_encoder_helper_funcs.disable,
    	 * &drm_encoder_helper_funcs.prepare or &drm_encoder_helper_funcs.dpms
    	 * hook.
    	 *
    	 * The bridge can assume that the display pipe (i.e. clocks and timing
    	 * signals) feeding it is still running when this callback is called.
    	 *
    	 * The @disable callback is optional.
    	 *
    	 * NOTE:
    	 *
    	 * This is deprecated, do not use!
    	 * New drivers shall use &drm_bridge_funcs.atomic_disable.
    	 */
    	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
    	 * &drm_encoder_helper_funcs.disable, &drm_encoder_helper_funcs.prepare
    	 * or &drm_encoder_helper_funcs.dpms hook.
    	 *
    	 * The bridge must assume that the display pipe (i.e. clocks and timing
    	 * signals) feeding it is no longer running when this callback is
    	 * called.
    	 *
    	 * The @post_disable callback is optional.
    	 *
    	 * NOTE:
    	 *
    	 * This is deprecated, do not use!
    	 * New drivers shall use &drm_bridge_funcs.atomic_post_disable.
    	 */
    	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. If the bridge is the first element
    	 * then this would be &drm_encoder_helper_funcs.mode_set. The display
    	 * pipe (i.e.  clocks and timing signals) is off when this function is
    	 * called.
    	 *
    	 * The adjusted_mode parameter is the mode output by the CRTC for the
    	 * first bridge in the chain. It can be different from the mode
    	 * parameter that contains the desired mode for the connector at the end
    	 * of the bridges chain, for instance when the first bridge in the chain
    	 * performs scaling. The adjusted mode is mostly useful for the first
    	 * bridge in the chain and is likely irrelevant for the other bridges.
    	 *
    	 * For atomic drivers the adjusted_mode is the mode stored in
    	 * &drm_crtc_state.adjusted_mode.
    	 *
    	 * NOTE:
    	 *
    	 * This is deprecated, do not use!
    	 * New drivers shall set their mode in the
    	 * &drm_bridge_funcs.atomic_enable operation.
    	 */
    	void (*mode_set)(struct drm_bridge *bridge,
    			 const struct drm_display_mode *mode,
    			 const 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
    	 * &drm_encoder_helper_funcs.enable, &drm_encoder_helper_funcs.commit or
    	 * &drm_encoder_helper_funcs.dpms hook.
    	 *
    	 * 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.
    	 *
    	 * The @pre_enable callback is optional.
    	 *
    	 * NOTE:
    	 *
    	 * This is deprecated, do not use!
    	 * New drivers shall use &drm_bridge_funcs.atomic_pre_enable.
    	 */
    	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
    	 * &drm_encoder_helper_funcs.enable, &drm_encoder_helper_funcs.commit or
    	 * &drm_encoder_helper_funcs.dpms hook.
    	 *
    	 * 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.
    	 *
    	 * The @enable callback is optional.
    	 *
    	 * NOTE:
    	 *
    	 * This is deprecated, do not use!
    	 * New drivers shall use &drm_bridge_funcs.atomic_enable.
    	 */
    	void (*enable)(struct drm_bridge *bridge);
    
    	/**
    	 * @atomic_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 @atomic_pre_enable or @pre_enable function. If the preceding
    	 * element is a &drm_encoder it's called right before the encoder's
    	 * &drm_encoder_helper_funcs.atomic_enable hook.
    	 *
    	 * 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.
    	 *
    	 * The @atomic_pre_enable callback is optional.
    	 */
    	void (*atomic_pre_enable)(struct drm_bridge *bridge,
    				  struct drm_bridge_state *old_bridge_state);
    
    	/**
    	 * @atomic_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 @atomic_enable or @enable function. If the preceding element
    	 * is a &drm_encoder it's called right after the encoder's
    	 * &drm_encoder_helper_funcs.atomic_enable hook.
    	 *
    	 * 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.
    	 *
    	 * The @atomic_enable callback is optional.
    	 */
    	void (*atomic_enable)(struct drm_bridge *bridge,
    			      struct drm_bridge_state *old_bridge_state);
    	/**
    	 * @atomic_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 @atomic_disable or @disable vfunc. If the preceding element
    	 * is a &drm_encoder it's called right before the
    	 * &drm_encoder_helper_funcs.atomic_disable hook.
    	 *
    	 * The bridge can assume that the display pipe (i.e. clocks and timing
    	 * signals) feeding it is still running when this callback is called.
    	 *
    	 * The @atomic_disable callback is optional.
    	 */
    	void (*atomic_disable)(struct drm_bridge *bridge,
    			       struct drm_bridge_state *old_bridge_state);
    
    	/**
    	 * @atomic_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
    	 * @atomic_post_disable or @post_disable function. If the preceding
    	 * element is a &drm_encoder it's called right after the encoder's
    	 * &drm_encoder_helper_funcs.atomic_disable hook.
    	 *
    	 * The bridge must assume that the display pipe (i.e. clocks and timing
    	 * signals) feeding it is no longer running when this callback is
    	 * called.
    	 *
    	 * The @atomic_post_disable callback is optional.
    	 */
    	void (*atomic_post_disable)(struct drm_bridge *bridge,
    				    struct drm_bridge_state *old_bridge_state);
    
    	/**
    	 * @atomic_duplicate_state:
    	 *
    	 * Duplicate the current bridge state object (which is guaranteed to be
    	 * non-NULL).
    	 *
    	 * The atomic_duplicate_state hook is mandatory if the bridge
    	 * implements any of the atomic hooks, and should be left unassigned
    	 * otherwise. For bridges that don't subclass &drm_bridge_state, the
    	 * drm_atomic_helper_bridge_duplicate_state() helper function shall be
    	 * used to implement this hook.
    	 *
    	 * RETURNS:
    	 * A valid drm_bridge_state object or NULL if the allocation fails.
    	 */
    	struct drm_bridge_state *(*atomic_duplicate_state)(struct drm_bridge *bridge);
    
    	/**
    	 * @atomic_destroy_state:
    	 *
    	 * Destroy a bridge state object previously allocated by
    	 * &drm_bridge_funcs.atomic_duplicate_state().
    	 *
    	 * The atomic_destroy_state hook is mandatory if the bridge implements
    	 * any of the atomic hooks, and should be left unassigned otherwise.
    	 * For bridges that don't subclass &drm_bridge_state, the
    	 * drm_atomic_helper_bridge_destroy_state() helper function shall be
    	 * used to implement this hook.
    	 */
    	void (*atomic_destroy_state)(struct drm_bridge *bridge,
    				     struct drm_bridge_state *state);
    
    	/**
    	 * @atomic_get_output_bus_fmts:
    	 *
    	 * Return the supported bus formats on the output end of a bridge.
    	 * The returned array must be allocated with kmalloc() and will be
    	 * freed by the caller. If the allocation fails, NULL should be
    	 * returned. num_output_fmts must be set to the returned array size.
    	 * Formats listed in the returned array should be listed in decreasing
    	 * preference order (the core will try all formats until it finds one
    	 * that works).
    	 *
    	 * This method is only called on the last element of the bridge chain
    	 * as part of the bus format negotiation process that happens in
    	 * &drm_atomic_bridge_chain_select_bus_fmts().
    	 * This method is optional. When not implemented, the core will
    	 * fall back to &drm_connector.display_info.bus_formats[0] if
    	 * &drm_connector.display_info.num_bus_formats > 0,
    	 * or to MEDIA_BUS_FMT_FIXED otherwise.
    	 */
    	u32 *(*atomic_get_output_bus_fmts)(struct drm_bridge *bridge,
    					   struct drm_bridge_state *bridge_state,
    					   struct drm_crtc_state *crtc_state,
    					   struct drm_connector_state *conn_state,
    					   unsigned int *num_output_fmts);
    
    	/**
    	 * @atomic_get_input_bus_fmts:
    	 *
    	 * Return the supported bus formats on the input end of a bridge for
    	 * a specific output bus format.
    	 *
    	 * The returned array must be allocated with kmalloc() and will be
    	 * freed by the caller. If the allocation fails, NULL should be
    	 * returned. num_input_fmts must be set to the returned array size.
    	 * Formats listed in the returned array should be listed in decreasing
    	 * preference order (the core will try all formats until it finds one
    	 * that works). When the format is not supported NULL should be
    	 * returned and num_input_fmts should be set to 0.
    	 *
    	 * This method is called on all elements of the bridge chain as part of
    	 * the bus format negotiation process that happens in
    	 * drm_atomic_bridge_chain_select_bus_fmts().
    	 * This method is optional. When not implemented, the core will bypass
    	 * bus format negotiation on this element of the bridge without
    	 * failing, and the previous element in the chain will be passed
    	 * MEDIA_BUS_FMT_FIXED as its output bus format.
    	 *
    	 * Bridge drivers that need to support being linked to bridges that are
    	 * not supporting bus format negotiation should handle the
    	 * output_fmt == MEDIA_BUS_FMT_FIXED case appropriately, by selecting a
    	 * sensible default value or extracting this information from somewhere
    	 * else (FW property, &drm_display_mode, &drm_display_info, ...)
    	 *
    	 * Note: Even if input format selection on the first bridge has no
    	 * impact on the negotiation process (bus format negotiation stops once
    	 * we reach the first element of the chain), drivers are expected to
    	 * return accurate input formats as the input format may be used to
    	 * configure the CRTC output appropriately.
    	 */
    	u32 *(*atomic_get_input_bus_fmts)(struct drm_bridge *bridge,
    					  struct drm_bridge_state *bridge_state,
    					  struct drm_crtc_state *crtc_state,
    					  struct drm_connector_state *conn_state,
    					  u32 output_fmt,
    					  unsigned int *num_input_fmts);
    
    	/**
    	 * @atomic_check:
    	 *
    	 * This method is responsible for checking bridge state correctness.
    	 * It can also check the state of the surrounding components in chain
    	 * to make sure the whole pipeline can work properly.
    	 *
    	 * &drm_bridge_funcs.atomic_check() hooks are called in reverse
    	 * order (from the last to the first bridge).
    	 *
    	 * This method is optional. &drm_bridge_funcs.mode_fixup() is not
    	 * called when &drm_bridge_funcs.atomic_check() is implemented, so only
    	 * one of them should be provided.
    	 *
    	 * If drivers need to tweak &drm_bridge_state.input_bus_cfg.flags or
    	 * &drm_bridge_state.output_bus_cfg.flags it should happen in
    	 * this function. By default the &drm_bridge_state.output_bus_cfg.flags
    	 * field is set to the next bridge
    	 * &drm_bridge_state.input_bus_cfg.flags value or
    	 * &drm_connector.display_info.bus_flags if the bridge is the last
    	 * element in the chain.
    	 *
    	 * RETURNS:
    	 * zero if the check passed, a negative error code otherwise.
    	 */
    	int (*atomic_check)(struct drm_bridge *bridge,
    			    struct drm_bridge_state *bridge_state,
    			    struct drm_crtc_state *crtc_state,
    			    struct drm_connector_state *conn_state);
    
    	/**
    	 * @atomic_reset:
    	 *
    	 * Reset the bridge to a predefined state (or retrieve its current
    	 * state) and return a &drm_bridge_state object matching this state.
    	 * This function is called at attach time.
    	 *
    	 * The atomic_reset hook is mandatory if the bridge implements any of
    	 * the atomic hooks, and should be left unassigned otherwise. For
    	 * bridges that don't subclass &drm_bridge_state, the
    	 * drm_atomic_helper_bridge_reset() helper function shall be used to
    	 * implement this hook.
    	 *
    	 * Note that the atomic_reset() semantics is not exactly matching the
    	 * reset() semantics found on other components (connector, plane, ...).
    	 *
    	 * 1. The reset operation happens when the bridge is attached, not when
    	 *    drm_mode_config_reset() is called
    	 * 2. It's meant to be used exclusively on bridges that have been
    	 *    converted to the ATOMIC API
    	 *
    	 * RETURNS:
    	 * A valid drm_bridge_state object in case of success, an ERR_PTR()
    	 * giving the reason of the failure otherwise.
    	 */
    	struct drm_bridge_state *(*atomic_reset)(struct drm_bridge *bridge);
    
    	/**
    	 * @detect:
    	 *
    	 * Check if anything is attached to the bridge output.
    	 *
    	 * This callback is optional, if not implemented the bridge will be
    	 * considered as always having a component attached to its output.
    	 * Bridges that implement this callback shall set the
    	 * DRM_BRIDGE_OP_DETECT flag in their &drm_bridge->ops.
    	 *
    	 * RETURNS:
    	 *
    	 * drm_connector_status indicating the bridge output status.
    	 */
    	enum drm_connector_status (*detect)(struct drm_bridge *bridge);
    
    	/**
    	 * @get_modes:
    	 *
    	 * Fill all modes currently valid for the sink into the &drm_connector
    	 * with drm_mode_probed_add().
    	 *
    	 * The @get_modes callback is mostly intended to support non-probeable
    	 * displays such as many fixed panels. Bridges that support reading
    	 * EDID shall leave @get_modes unimplemented and implement the
    	 * &drm_bridge_funcs->edid_read callback instead.
    	 *
    	 * This callback is optional. Bridges that implement it shall set the
    	 * DRM_BRIDGE_OP_MODES flag in their &drm_bridge->ops.
    	 *
    	 * The connector parameter shall be used for the sole purpose of
    	 * filling modes, and shall not be stored internally by bridge drivers
    	 * for future usage.
    	 *
    	 * RETURNS:
    	 *
    	 * The number of modes added by calling drm_mode_probed_add().
    	 */
    	int (*get_modes)(struct drm_bridge *bridge,
    			 struct drm_connector *connector);
    
    	/**
    	 * @edid_read:
    	 *
    	 * Read the EDID data of the connected display.
    	 *
    	 * The @edid_read callback is the preferred way of reporting mode
    	 * information for a display connected to the bridge output. Bridges
    	 * that support reading EDID shall implement this callback and leave
    	 * the @get_modes callback unimplemented.
    	 *
    	 * The caller of this operation shall first verify the output
    	 * connection status and refrain from reading EDID from a disconnected
    	 * output.
    	 *
    	 * This callback is optional. Bridges that implement it shall set the
    	 * DRM_BRIDGE_OP_EDID flag in their &drm_bridge->ops.
    	 *
    	 * The connector parameter shall be used for the sole purpose of EDID
    	 * retrieval, and shall not be stored internally by bridge drivers for
    	 * future usage.
    	 *
    	 * RETURNS:
    	 *
    	 * An edid structure newly allocated with drm_edid_alloc() or returned
    	 * from drm_edid_read() family of functions on success, or NULL
    	 * otherwise. The caller is responsible for freeing the returned edid
    	 * structure with drm_edid_free().
    	 */
    	const struct drm_edid *(*edid_read)(struct drm_bridge *bridge,
    					    struct drm_connector *connector);
    
    	/**
    	 * @hpd_notify:
    	 *
    	 * Notify the bridge of hot plug detection.
    	 *
    	 * This callback is optional, it may be implemented by bridges that
    	 * need to be notified of display connection or disconnection for
    	 * internal reasons. One use case is to reset the internal state of CEC
    	 * controllers for HDMI bridges.
    	 */
    	void (*hpd_notify)(struct drm_bridge *bridge,
    			   enum drm_connector_status status);
    
    	/**
    	 * @hpd_enable:
    	 *
    	 * Enable hot plug detection. From now on the bridge shall call
    	 * drm_bridge_hpd_notify() each time a change is detected in the output
    	 * connection status, until hot plug detection gets disabled with
    	 * @hpd_disable.
    	 *
    	 * This callback is optional and shall only be implemented by bridges
    	 * that support hot-plug notification without polling. Bridges that
    	 * implement it shall also implement the @hpd_disable callback and set
    	 * the DRM_BRIDGE_OP_HPD flag in their &drm_bridge->ops.
    	 */
    	void (*hpd_enable)(struct drm_bridge *bridge);
    
    	/**
    	 * @hpd_disable:
    	 *
    	 * Disable hot plug detection. Once this function returns the bridge
    	 * shall not call drm_bridge_hpd_notify() when a change in the output
    	 * connection status occurs.
    	 *
    	 * This callback is optional and shall only be implemented by bridges
    	 * that support hot-plug notification without polling. Bridges that
    	 * implement it shall also implement the @hpd_enable callback and set
    	 * the DRM_BRIDGE_OP_HPD flag in their &drm_bridge->ops.
    	 */
    	void (*hpd_disable)(struct drm_bridge *bridge);
    
    	/**
    	 * @hdmi_tmds_char_rate_valid:
    	 *
    	 * Check whether a particular TMDS character rate is supported by the
    	 * driver.
    	 *
    	 * This callback is optional and should only be implemented by the
    	 * bridges that take part in the HDMI connector implementation. Bridges
    	 * that implement it shall set the DRM_BRIDGE_OP_HDMI flag in their
    	 * &drm_bridge->ops.
    	 *
    	 * Returns:
    	 *
    	 * Either &drm_mode_status.MODE_OK or one of the failure reasons
    	 * in &enum drm_mode_status.
    	 */
    	enum drm_mode_status
    	(*hdmi_tmds_char_rate_valid)(const struct drm_bridge *bridge,
    				     const struct drm_display_mode *mode,
    				     unsigned long long tmds_rate);
    
    	/**
    	 * @hdmi_clear_infoframe:
    	 *
    	 * This callback clears the infoframes in the hardware during commit.
    	 * It will be called multiple times, once for every disabled infoframe
    	 * type.
    	 *
    	 * This callback is optional but it must be implemented by bridges that
    	 * set the DRM_BRIDGE_OP_HDMI flag in their &drm_bridge->ops.
    	 */
    	int (*hdmi_clear_infoframe)(struct drm_bridge *bridge,
    				    enum hdmi_infoframe_type type);
    	/**
    	 * @hdmi_write_infoframe:
    	 *
    	 * Program the infoframe into the hardware. It will be called multiple
    	 * times, once for every updated infoframe type.
    	 *
    	 * This callback is optional but it must be implemented by bridges that
    	 * set the DRM_BRIDGE_OP_HDMI flag in their &drm_bridge->ops.
    	 */
    	int (*hdmi_write_infoframe)(struct drm_bridge *bridge,
    				    enum hdmi_infoframe_type type,
    				    const u8 *buffer, size_t len);
    
    	/**
    	 * @debugfs_init:
    	 *
    	 * Allows bridges to create bridge-specific debugfs files.
    	 */
    	void (*debugfs_init)(struct drm_bridge *bridge, struct dentry *root);
    };
    
    /**
     * struct drm_bridge_timings - timing information for the bridge
     */
    struct drm_bridge_timings {
    	/**
    	 * @input_bus_flags:
    	 *
    	 * Tells what additional settings for the pixel data on the bus
    	 * this bridge requires (like pixel signal polarity). See also
    	 * &drm_display_info->bus_flags.
    	 */
    	u32 input_bus_flags;
    	/**
    	 * @setup_time_ps:
    	 *
    	 * Defines the time in picoseconds the input data lines must be
    	 * stable before the clock edge.
    	 */
    	u32 setup_time_ps;
    	/**
    	 * @hold_time_ps:
    	 *
    	 * Defines the time in picoseconds taken for the bridge to sample the
    	 * input signal after the clock edge.
    	 */
    	u32 hold_time_ps;
    	/**
    	 * @dual_link:
    	 *
    	 * True if the bus operates in dual-link mode. The exact meaning is
    	 * dependent on the bus type. For LVDS buses, this indicates that even-
    	 * and odd-numbered pixels are received on separate links.
    	 */
    	bool dual_link;
    };
    
    /**
     * enum drm_bridge_ops - Bitmask of operations supported by the bridge
     */
    enum drm_bridge_ops {
    	/**
    	 * @DRM_BRIDGE_OP_DETECT: The bridge can detect displays connected to
    	 * its output. Bridges that set this flag shall implement the
    	 * &drm_bridge_funcs->detect callback.
    	 */
    	DRM_BRIDGE_OP_DETECT = BIT(0),
    	/**
    	 * @DRM_BRIDGE_OP_EDID: The bridge can retrieve the EDID of the display
    	 * connected to its output. Bridges that set this flag shall implement
    	 * the &drm_bridge_funcs->edid_read callback.
    	 */
    	DRM_BRIDGE_OP_EDID = BIT(1),
    	/**
    	 * @DRM_BRIDGE_OP_HPD: The bridge can detect hot-plug and hot-unplug
    	 * without requiring polling. Bridges that set this flag shall
    	 * implement the &drm_bridge_funcs->hpd_enable and
    	 * &drm_bridge_funcs->hpd_disable callbacks if they support enabling
    	 * and disabling hot-plug detection dynamically.
    	 */
    	DRM_BRIDGE_OP_HPD = BIT(2),
    	/**
    	 * @DRM_BRIDGE_OP_MODES: The bridge can retrieve the modes supported
    	 * by the display at its output. This does not include reading EDID
    	 * which is separately covered by @DRM_BRIDGE_OP_EDID. Bridges that set
    	 * this flag shall implement the &drm_bridge_funcs->get_modes callback.
    	 */
    	DRM_BRIDGE_OP_MODES = BIT(3),
    	/**
    	 * @DRM_BRIDGE_OP_HDMI: The bridge provides HDMI connector operations,
    	 * including infoframes support. Bridges that set this flag must
    	 * implement the &drm_bridge_funcs->write_infoframe callback.
    	 *
    	 * Note: currently there can be at most one bridge in a chain that sets
    	 * this bit. This is to simplify corresponding glue code in connector
    	 * drivers.
    	 */
    	DRM_BRIDGE_OP_HDMI = BIT(4),
    };
    
    /**
     * struct drm_bridge - central DRM bridge control structure
     */
    struct drm_bridge {
    	/** @base: inherit from &drm_private_object */
    	struct drm_private_obj base;
    	/** @dev: DRM device this bridge belongs to */
    	struct drm_device *dev;
    	/** @encoder: encoder to which this bridge is connected */
    	struct drm_encoder *encoder;
    	/** @chain_node: used to form a bridge chain */
    	struct list_head chain_node;
    	/** @of_node: device node pointer to the bridge */
    	struct device_node *of_node;
    	/** @list: to keep track of all added bridges */
    	struct list_head list;
    	/**
    	 * @timings:
    	 *
    	 * the timing specification for the bridge, if any (may be NULL)
    	 */
    	const struct drm_bridge_timings *timings;
    	/** @funcs: control functions */
    	const struct drm_bridge_funcs *funcs;
    	/** @driver_private: pointer to the bridge driver's internal context */
    	void *driver_private;
    	/** @ops: bitmask of operations supported by the bridge */
    	enum drm_bridge_ops ops;
    	/**
    	 * @type: Type of the connection at the bridge output
    	 * (DRM_MODE_CONNECTOR_*). For bridges at the end of this chain this
    	 * identifies the type of connected display.
    	 */
    	int type;
    	/**
    	 * @interlace_allowed: Indicate that the bridge can handle interlaced
    	 * modes.
    	 */
    	bool interlace_allowed;
    	/**
    	 * @pre_enable_prev_first: The bridge requires that the prev
    	 * bridge @pre_enable function is called before its @pre_enable,
    	 * and conversely for post_disable. This is most frequently a
    	 * requirement for DSI devices which need the host to be initialised
    	 * before the peripheral.
    	 */
    	bool pre_enable_prev_first;
    	/**
    	 * @ddc: Associated I2C adapter for DDC access, if any.
    	 */
    	struct i2c_adapter *ddc;
    	/** private: */
    	/**
    	 * @hpd_mutex: Protects the @hpd_cb and @hpd_data fields.
    	 */
    	struct mutex hpd_mutex;
    	/**
    	 * @hpd_cb: Hot plug detection callback, registered with
    	 * drm_bridge_hpd_enable().
    	 */
    	void (*hpd_cb)(void *data, enum drm_connector_status status);
    	/**
    	 * @hpd_data: Private data passed to the Hot plug detection callback
    	 * @hpd_cb.
    	 */
    	void *hpd_data;
    
    	/**
    	 * @vendor: Vendor of the product to be used for the SPD InfoFrame
    	 * generation. This is required if @DRM_BRIDGE_OP_HDMI is set.
    	 */
    	const char *vendor;
    
    	/**
    	 * @product: Name of the product to be used for the SPD InfoFrame
    	 * generation. This is required if @DRM_BRIDGE_OP_HDMI is set.
    	 */
    	const char *product;
    
    	/**
    	 * @supported_formats: Bitmask of @hdmi_colorspace listing supported
    	 * output formats. This is only relevant if @DRM_BRIDGE_OP_HDMI is set.
    	 */
    	unsigned int supported_formats;
    
    	/**
    	 * @max_bpc: Maximum bits per char the HDMI bridge supports. Allowed
    	 * values are 8, 10 and 12. This is only relevant if
    	 * @DRM_BRIDGE_OP_HDMI is set.
    	 */
    	unsigned int max_bpc;
    };
    
    static inline struct drm_bridge *
    drm_priv_to_bridge(struct drm_private_obj *priv)
    {
    	return container_of(priv, struct drm_bridge, base);
    }
    
    void drm_bridge_add(struct drm_bridge *bridge);
    int devm_drm_bridge_add(struct device *dev, struct drm_bridge *bridge);
    void drm_bridge_remove(struct drm_bridge *bridge);
    int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
    		      struct drm_bridge *previous,
    		      enum drm_bridge_attach_flags flags);
    
    #ifdef CONFIG_OF
    struct drm_bridge *of_drm_find_bridge(struct device_node *np);
    #else
    static inline struct drm_bridge *of_drm_find_bridge(struct device_node *np)
    {
    	return NULL;
    }
    #endif
    
    /**
     * drm_bridge_get_next_bridge() - Get the next bridge in the chain
     * @bridge: bridge object
     *
     * RETURNS:
     * the next bridge in the chain after @bridge, or NULL if @bridge is the last.
     */
    static inline struct drm_bridge *
    drm_bridge_get_next_bridge(struct drm_bridge *bridge)
    {
    	if (list_is_last(&bridge->chain_node, &bridge->encoder->bridge_chain))
    		return NULL;
    
    	return list_next_entry(bridge, chain_node);
    }
    
    /**
     * drm_bridge_get_prev_bridge() - Get the previous bridge in the chain
     * @bridge: bridge object
     *
     * RETURNS:
     * the previous bridge in the chain, or NULL if @bridge is the first.
     */
    static inline struct drm_bridge *
    drm_bridge_get_prev_bridge(struct drm_bridge *bridge)
    {
    	if (list_is_first(&bridge->chain_node, &bridge->encoder->bridge_chain))
    		return NULL;
    
    	return list_prev_entry(bridge, chain_node);
    }
    
    /**
     * drm_bridge_chain_get_first_bridge() - Get the first bridge in the chain
     * @encoder: encoder object
     *
     * RETURNS:
     * the first bridge in the chain, or NULL if @encoder has no bridge attached
     * to it.
     */
    static inline struct drm_bridge *
    drm_bridge_chain_get_first_bridge(struct drm_encoder *encoder)
    {
    	return list_first_entry_or_null(&encoder->bridge_chain,
    					struct drm_bridge, chain_node);
    }
    
    /**
     * drm_for_each_bridge_in_chain() - Iterate over all bridges present in a chain
     * @encoder: the encoder to iterate bridges on
     * @bridge: a bridge pointer updated to point to the current bridge at each
     *	    iteration
     *
     * Iterate over all bridges present in the bridge chain attached to @encoder.
     */
    #define drm_for_each_bridge_in_chain(encoder, bridge)			\
    	list_for_each_entry(bridge, &(encoder)->bridge_chain, chain_node)
    
    enum drm_mode_status
    drm_bridge_chain_mode_valid(struct drm_bridge *bridge,
    			    const struct drm_display_info *info,
    			    const struct drm_display_mode *mode);
    void drm_bridge_chain_mode_set(struct drm_bridge *bridge,
    			       const struct drm_display_mode *mode,
    			       const struct drm_display_mode *adjusted_mode);
    
    int drm_atomic_bridge_chain_check(struct drm_bridge *bridge,
    				  struct drm_crtc_state *crtc_state,
    				  struct drm_connector_state *conn_state);
    void drm_atomic_bridge_chain_disable(struct drm_bridge *bridge,
    				     struct drm_atomic_state *state);
    void drm_atomic_bridge_chain_post_disable(struct drm_bridge *bridge,
    					  struct drm_atomic_state *state);
    void drm_atomic_bridge_chain_pre_enable(struct drm_bridge *bridge,
    					struct drm_atomic_state *state);
    void drm_atomic_bridge_chain_enable(struct drm_bridge *bridge,
    				    struct drm_atomic_state *state);
    
    u32 *
    drm_atomic_helper_bridge_propagate_bus_fmt(struct drm_bridge *bridge,
    					struct drm_bridge_state *bridge_state,
    					struct drm_crtc_state *crtc_state,
    					struct drm_connector_state *conn_state,
    					u32 output_fmt,
    					unsigned int *num_input_fmts);
    
    enum drm_connector_status drm_bridge_detect(struct drm_bridge *bridge);
    int drm_bridge_get_modes(struct drm_bridge *bridge,
    			 struct drm_connector *connector);
    const struct drm_edid *drm_bridge_edid_read(struct drm_bridge *bridge,
    					    struct drm_connector *connector);
    void drm_bridge_hpd_enable(struct drm_bridge *bridge,
    			   void (*cb)(void *data,
    				      enum drm_connector_status status),
    			   void *data);
    void drm_bridge_hpd_disable(struct drm_bridge *bridge);
    void drm_bridge_hpd_notify(struct drm_bridge *bridge,
    			   enum drm_connector_status status);
    
    #ifdef CONFIG_DRM_PANEL_BRIDGE
    bool drm_bridge_is_panel(const struct drm_bridge *bridge);
    struct drm_bridge *drm_panel_bridge_add(struct drm_panel *panel);
    struct drm_bridge *drm_panel_bridge_add_typed(struct drm_panel *panel,
    					      u32 connector_type);
    void drm_panel_bridge_remove(struct drm_bridge *bridge);
    int drm_panel_bridge_set_orientation(struct drm_connector *connector,
    				     struct drm_bridge *bridge);
    struct drm_bridge *devm_drm_panel_bridge_add(struct device *dev,
    					     struct drm_panel *panel);
    struct drm_bridge *devm_drm_panel_bridge_add_typed(struct device *dev,
    						   struct drm_panel *panel,
    						   u32 connector_type);
    struct drm_bridge *drmm_panel_bridge_add(struct drm_device *drm,
    					     struct drm_panel *panel);
    struct drm_connector *drm_panel_bridge_connector(struct drm_bridge *bridge);
    #else
    static inline bool drm_bridge_is_panel(const struct drm_bridge *bridge)
    {
    	return false;
    }
    
    static inline int drm_panel_bridge_set_orientation(struct drm_connector *connector,
    						   struct drm_bridge *bridge)
    {
    	return -EINVAL;
    }
    #endif
    
    #if defined(CONFIG_OF) && defined(CONFIG_DRM_PANEL_BRIDGE)
    struct drm_bridge *devm_drm_of_get_bridge(struct device *dev, struct device_node *node,
    					  u32 port, u32 endpoint);
    struct drm_bridge *drmm_of_get_bridge(struct drm_device *drm, struct device_node *node,
    					  u32 port, u32 endpoint);
    #else
    static inline struct drm_bridge *devm_drm_of_get_bridge(struct device *dev,
    							struct device_node *node,
    							u32 port,
    							u32 endpoint)
    {
    	return ERR_PTR(-ENODEV);
    }
    
    static inline struct drm_bridge *drmm_of_get_bridge(struct drm_device *drm,
    						     struct device_node *node,
    						     u32 port,
    						     u32 endpoint)
    {
    	return ERR_PTR(-ENODEV);
    }
    #endif
    
    #endif