drm: Document drm_encoder/crtc_helper_funcs (36b66080) · Commits · e / devices / android_kernel_fairphone_FP3

include/drm/drm_modeset_helper_vtables.h

+401 −48

Original line number	Diff line number	Diff line
		@@ -51,58 +51,236 @@ enum mode_set_atomic;

		/**
		* struct drm_crtc_helper_funcs - helper operations for CRTCs
		* @dpms: set power state
		* @prepare: prepare the CRTC, called before @mode_set
		* @commit: commit changes to CRTC, called after @mode_set
		* @mode_fixup: try to fixup proposed mode for this CRTC
		* @mode_set: set this mode
		* @mode_set_nofb: set mode only (no scanout buffer attached)
		* @mode_set_base: update the scanout buffer
		* @mode_set_base_atomic: non-blocking mode set (used for kgdb support)
		* @load_lut: load color palette
		* @disable: disable CRTC when no longer in use
		* @enable: enable CRTC
		*
		* The helper operations are called by the mid-layer CRTC helper.
		*
		* Note that with atomic helpers @dpms, @prepare and @commit hooks are
		* deprecated. Used @enable and @disable instead exclusively.
		*
		* With legacy crtc helpers there's a big semantic difference between @disable
		* and the other hooks: @disable also needs to release any resources acquired in
		* @mode_set (like shared PLLs).
		*
		* These hooks are used by the legacy CRTC helpers, the transitional plane
		* helpers and the new atomic modesetting helpers.
		*/
		struct drm_crtc_helper_funcs {
		/*
		* Control power levels on the CRTC. If the mode passed in is
		* unsupported, the provider must use the next lowest power level.
		/**
		* @dpms:
		*
		* Callback to control power levels on the CRTC. If the mode passed in
		* is unsupported, the provider must use the next lowest power level.
		* This is used by the legacy CRTC helpers to implement DPMS
		* functionality in drm_helper_connector_dpms().
		*
		* This callback is also used to disable a CRTC by calling it with
		* DRM_MODE_DPMS_OFF if the @disable hook isn't used.
		*
		* This callback is used by the legacy CRTC helpers. Atomic helpers
		* also support using this hook for enabling and disabling a CRTC to
		* facilitate transitions to atomic, but it is deprecated. Instead
		* @enable and @disable should be used.
		*/
		void (dpms)(struct drm_crtc crtc, int mode);

		/**
		* @prepare:
		*
		* This callback should prepare the CRTC for a subsequent modeset, which
		* in practice means the driver should disable the CRTC if it is
		* running. Most drivers ended up implementing this by calling their
		* @dpms hook with DRM_MODE_DPMS_OFF.
		*
		* This callback is used by the legacy CRTC helpers. Atomic helpers
		* also support using this hook for disabling a CRTC to facilitate
		* transitions to atomic, but it is deprecated. Instead @disable should
		* be used.
		*/
		void (prepare)(struct drm_crtc crtc);

		/**
		* @commit:
		*
		* This callback should commit the new mode on the CRTC after a modeset,
		* which in practice means the driver should enable the CRTC. Most
		* drivers ended up implementing this by calling their @dpms hook with
		* DRM_MODE_DPMS_ON.
		*
		* This callback is used by the legacy CRTC helpers. Atomic helpers
		* also support using this hook for enabling a CRTC to facilitate
		* transitions to atomic, but it is deprecated. Instead @enable should
		* be used.
		*/
		void (commit)(struct drm_crtc crtc);

		/* Provider can fixup or change mode timings before modeset occurs */
		/**
		* @mode_fixup:
		*
		* This callback is used to validate a mode. The parameter mode is the
		* display mode that userspace requested, adjusted_mode is the mode the
		* encoders need to be fed with. Note that this is the inverse semantics
		* of the meaning for the &drm_encoder and &drm_bridge
		* ->mode_fixup() functions. If the CRTC cannot support the requested
		* conversion from mode to adjusted_mode it should reject the modeset.
		*
		* This function is used by both legacy CRTC helpers and atomic helpers.
		* With atomic helpers it is optional.
		*
		* 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). Atomic drivers
		* MUST NOT touch any persistent state (hardware or software) or data
		* structures except the passed in adjusted_mode parameter.
		*
		* This is in contrast to the legacy CRTC helpers where this was
		* allowed.
		*
		* Atomic drivers which need to inspect and adjust more state should
		* instead use the @atomic_check callback.
		*
		* RETURNS:
		*
		* True if an acceptable configuration is possible, false if the modeset
		* operation should be rejected.
		*/
		bool (mode_fixup)(struct drm_crtc crtc,
		const struct drm_display_mode *mode,
		struct drm_display_mode *adjusted_mode);
		/* Actually set the mode */

		/**
		* @mode_set:
		*
		* This callback is used by the legacy CRTC helpers to set a new mode,
		* position and framebuffer. Since it ties the primary plane to every
		* mode change it is incompatible with universal plane support. And
		* since it can't update other planes it's incompatible with atomic
		* modeset support.
		*
		* This callback is only used by CRTC helpers and deprecated.
		*
		* RETURNS:
		*
		* 0 on success or a negative error code on failure.
		*/
		int (mode_set)(struct drm_crtc crtc, struct drm_display_mode *mode,
		struct drm_display_mode *adjusted_mode, int x, int y,
		struct drm_framebuffer *old_fb);
		/* Actually set the mode for atomic helpers, optional */

		/**
		* @mode_set_nofb:
		*
		* This callback is used to update the display mode of a CRTC without
		* changing anything of the primary plane configuration. This fits the
		* requirement of atomic and hence is used by the atomic helpers. It is
		* also used by the transitional plane helpers to implement a
		* @mode_set hook in drm_helper_crtc_mode_set().
		*
		* Note that the display pipe is completely off when this function is
		* called. Atomic drivers which need hardware to be running before they
		* program the new display mode (e.g. because they implement runtime PM)
		* should not use this hook. This is because the helper library calls
		* this hook only once per mode change and not every time the display
		* pipeline is suspended using either DPMS or the new "ACTIVE" property.
		* Which means register values set in this callback might get reset when
		* the CRTC is suspended, but not restored. Such drivers should instead
		* move all their CRTC setup into the @enable callback.
		*
		* This callback is optional.
		*/
		void (mode_set_nofb)(struct drm_crtc crtc);

		/* Move the crtc on the current fb to the given position optional */
		/**
		* @mode_set_base:
		*
		* This callback is used by the legacy CRTC helpers to set a new
		* framebuffer and scanout position. It is optional and used as an
		* optimized fast-path instead of a full mode set operation with all the
		* resulting flickering. Since it can't update other planes it's
		* incompatible with atomic modeset support.
		*
		* This callback is only used by the CRTC helpers and deprecated.
		*
		* RETURNS:
		*
		* 0 on success or a negative error code on failure.
		*/
		int (mode_set_base)(struct drm_crtc crtc, int x, int y,
		struct drm_framebuffer *old_fb);

		/**
		* @mode_set_base_atomic:
		*
		* This callback is used by the fbdev helpers to set a new framebuffer
		* and scanout without sleeping, i.e. from an atomic calling context. It
		* is only used to implement kgdb support.
		*
		* This callback is optional and only needed for kgdb support in the fbdev
		* helpers.
		*
		* RETURNS:
		*
		* 0 on success or a negative error code on failure.
		*/
		int (mode_set_base_atomic)(struct drm_crtc crtc,
		struct drm_framebuffer *fb, int x, int y,
		enum mode_set_atomic);

		/* reload the current crtc LUT */
		/**
		* @load_lut:
		*
		* Load a LUT prepared with the @gamma_set functions from
		* &drm_fb_helper_funcs.
		*
		* This callback is optional and is only used by the fbdev emulation
		* helpers.
		*
		* FIXME:
		*
		* This callback is functionally redundant with the core gamma table
		* support and simply exists because the fbdev hasn't yet been
		* refactored to use the core gamma table interfaces.
		*/
		void (load_lut)(struct drm_crtc crtc);

		/**
		* @disable:
		*
		* This callback should be used to disable the CRTC. With the atomic
		* drivers it is called after all encoders connected to this CRTC have
		* been shut off already using their own ->disable hook. If that
		* sequence is too simple drivers can just add their own hooks and call
		* it from this CRTC callback here by looping over all encoders
		* connected to it using for_each_encoder_on_crtc().
		*
		* This hook is used both by legacy CRTC helpers and atomic helpers.
		* Atomic drivers don't need to implement it if there's no need to
		* disable anything at the CRTC level. To ensure that runtime PM
		* handling (using either DPMS or the new "ACTIVE" property) works
		* @disable must be the inverse of @enable for atomic drivers.
		*
		* NOTE:
		*
		* With legacy CRTC helpers there's a big semantic difference between
		* @disable and other hooks (like @prepare or @dpms) used to shut down a
		* CRTC: @disable is only called when also logically disabling the
		* display pipeline and needs to release any resources acquired in
		* @mode_set (like shared PLLs, or again release pinned framebuffers).
		*
		* Therefore @disable must be the inverse of @mode_set plus @commit for
		* drivers still using legacy CRTC helpers, which is different from the
		* rules under atomic.
		*/
		void (disable)(struct drm_crtc crtc);

		/**
		* @enable:
		*
		* This callback should be used to enable the CRTC. With the atomic
		* drivers it is called before all encoders connected to this CRTC are
		* enabled through the encoder's own ->enable hook. If that sequence is
		* too simple drivers can just add their own hooks and call it from this
		* CRTC callback here by looping over all encoders connected to it using
		* for_each_encoder_on_crtc().
		*
		* This hook is used only by atomic helpers, for symmetry with @disable.
		* Atomic drivers don't need to implement it if there's no need to
		* enable anything at the CRTC level. To ensure that runtime PM handling
		* (using either DPMS or the new "ACTIVE" property) works
		* @enable must be the inverse of @disable for atomic drivers.
		*/
		void (enable)(struct drm_crtc crtc);

		/**
		@@ -212,53 +390,228 @@ static inline void drm_crtc_helper_add(struct drm_crtc *crtc,

		/**
		* struct drm_encoder_helper_funcs - helper operations for encoders
		* @dpms: set power state
		* @mode_fixup: try to fixup proposed mode for this connector
		* @prepare: part of the disable sequence, called before the CRTC modeset
		* @commit: called after the CRTC modeset
		* @mode_set: set this mode, optional for atomic helpers
		* @get_crtc: return CRTC that the encoder is currently attached to
		* @detect: connection status detection
		* @disable: disable encoder when not in use (overrides DPMS off)
		* @enable: enable encoder
		* @atomic_check: check for validity of an atomic update
		*
		* The helper operations are called by the mid-layer CRTC helper.
		*
		* Note that with atomic helpers @dpms, @prepare and @commit hooks are
		* deprecated. Used @enable and @disable instead exclusively.
		*
		* With legacy crtc helpers there's a big semantic difference between @disable
		* and the other hooks: @disable also needs to release any resources acquired in
		* @mode_set (like shared PLLs).
		*
		* These hooks are used by the legacy CRTC helpers, the transitional plane
		* helpers and the new atomic modesetting helpers.
		*/
		struct drm_encoder_helper_funcs {
		/**
		* @dpms:
		*
		* Callback to control power levels on the encoder. If the mode passed in
		* is unsupported, the provider must use the next lowest power level.
		* This is used by the legacy encoder helpers to implement DPMS
		* functionality in drm_helper_connector_dpms().
		*
		* This callback is also used to disable an encoder by calling it with
		* DRM_MODE_DPMS_OFF if the @disable hook isn't used.
		*
		* This callback is used by the legacy CRTC helpers. Atomic helpers
		* also support using this hook for enabling and disabling an encoder to
		* facilitate transitions to atomic, but it is deprecated. Instead
		* @enable and @disable should be used.
		*/
		void (dpms)(struct drm_encoder encoder, int 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 a &drm_bridge.
		* The parameter adjusted_mode is the input mode the encoder requires. It
		* can be modified by this callback and does not need to match mode.
		*
		* This function is used by both legacy CRTC helpers and atomic helpers.
		* With atomic helpers it is optional.
		*
		* 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). Atomic drivers
		* MUST NOT touch any persistent state (hardware or software) or data
		* structures except the passed in adjusted_mode parameter.
		*
		* This is in contrast to the legacy CRTC helpers where this was
		* allowed.
		*
		* Atomic drivers which need to inspect and adjust more state should
		* instead use the @atomic_check callback.
		*
		* RETURNS:
		*
		* True if an acceptable configuration is possible, false if the modeset
		* operation should be rejected.
		*/
		bool (mode_fixup)(struct drm_encoder encoder,
		const struct drm_display_mode *mode,
		struct drm_display_mode *adjusted_mode);

		/**
		* @prepare:
		*
		* This callback should prepare the encoder for a subsequent modeset,
		* which in practice means the driver should disable the encoder if it
		* is running. Most drivers ended up implementing this by calling their
		* @dpms hook with DRM_MODE_DPMS_OFF.
		*
		* This callback is used by the legacy CRTC helpers. Atomic helpers
		* also support using this hook for disabling an encoder to facilitate
		* transitions to atomic, but it is deprecated. Instead @disable should
		* be used.
		*/
		void (prepare)(struct drm_encoder encoder);

		/**
		* @commit:
		*
		* This callback should commit the new mode on the encoder after a modeset,
		* which in practice means the driver should enable the encoder. Most
		* drivers ended up implementing this by calling their @dpms hook with
		* DRM_MODE_DPMS_ON.
		*
		* This callback is used by the legacy CRTC helpers. Atomic helpers
		* also support using this hook for enabling an encoder to facilitate
		* transitions to atomic, but it is deprecated. Instead @enable should
		* be used.
		*/
		void (commit)(struct drm_encoder encoder);

		/**
		* @mode_set:
		*
		* This callback is used to update the display mode of an encoder.
		*
		* Note that the display pipe is completely off when this function is
		* called. Drivers which need hardware to be running before they program
		* the new display mode (because they implement runtime PM) should not
		* use this hook, because the helper library calls it only once and not
		* every time the display pipeline is suspend using either DPMS or the
		* new "ACTIVE" property. Such drivers should instead move all their
		* encoder setup into the ->enable() callback.
		*
		* This callback is used both by the legacy CRTC helpers and the atomic
		* modeset helpers. It is optional in the atomic helpers.
		*/
		void (mode_set)(struct drm_encoder encoder,
		struct drm_display_mode *mode,
		struct drm_display_mode *adjusted_mode);

		/**
		* @get_crtc:
		*
		* This callback is used by the legacy CRTC helpers to work around
		* deficiencies in its own book-keeping.
		*
		* Do not use, use atomic helpers instead, which get the book keeping
		* right.
		*
		* FIXME:
		*
		* Currently only nouveau is using this, and as soon as nouveau is
		* atomic we can ditch this hook.
		*/
		struct drm_crtc (get_crtc)(struct drm_encoder *encoder);
		/* detect for DAC style encoders */

		/**
		* @detect:
		*
		* This callback can be used by drivers who want to do detection on the
		* encoder object instead of in connector functions.
		*
		* It is not used by any helper and therefore has purely driver-specific
		* semantics. New drivers shouldn't use this and instead just implement
		* their own private callbacks.
		*
		* FIXME:
		*
		* This should just be converted into a pile of driver vfuncs.
		* Currently radeon, amdgpu and nouveau are using it.
		*/
		enum drm_connector_status (detect)(struct drm_encoder encoder,
		struct drm_connector *connector);

		/**
		* @disable:
		*
		* This callback should be used to disable the encoder. With the atomic
		* drivers it is called before this encoder's CRTC has been shut off
		* using the CRTC's own ->disable hook. If that sequence is too simple
		* drivers can just add their own driver private encoder hooks and call
		* them from CRTC's callback by looping over all encoders connected to
		* it using for_each_encoder_on_crtc().
		*
		* This hook is used both by legacy CRTC helpers and atomic helpers.
		* Atomic drivers don't need to implement it if there's no need to
		* disable anything at the encoder level. To ensure that runtime PM
		* handling (using either DPMS or the new "ACTIVE" property) works
		* @disable must be the inverse of @enable for atomic drivers.
		*
		* NOTE:
		*
		* With legacy CRTC helpers there's a big semantic difference between
		* @disable and other hooks (like @prepare or @dpms) used to shut down a
		* encoder: @disable is only called when also logically disabling the
		* display pipeline and needs to release any resources acquired in
		* @mode_set (like shared PLLs, or again release pinned framebuffers).
		*
		* Therefore @disable must be the inverse of @mode_set plus @commit for
		* drivers still using legacy CRTC helpers, which is different from the
		* rules under atomic.
		*/
		void (disable)(struct drm_encoder encoder);

		/**
		* @enable:
		*
		* This callback should be used to enable the encoder. With the atomic
		* drivers it is called after this encoder's CRTC has been enabled using
		* the CRTC's own ->enable hook. If that sequence is too simple drivers
		* can just add their own driver private encoder hooks and call them
		* from CRTC's callback by looping over all encoders connected to it
		* using for_each_encoder_on_crtc().
		*
		* This hook is used only by atomic helpers, for symmetry with @disable.
		* Atomic drivers don't need to implement it if there's no need to
		* enable anything at the encoder level. To ensure that runtime PM handling
		* (using either DPMS or the new "ACTIVE" property) works
		* @enable must be the inverse of @disable for atomic drivers.
		*/
		void (enable)(struct drm_encoder encoder);

		/* atomic helpers */
		/**
		* @atomic_check:
		*
		* This callback is used to validate encoder state for atomic drivers.
		* Since the encoder is the object connecting the CRTC and connector it
		* gets passed both states, to be able to validate interactions and
		* update the CRTC to match what the encoder needs for the requested
		* connector.
		*
		* This function is used by the atomic helpers, but it is optional.
		*
		* NOTE:
		*
		* This function is called in the check phase of an atomic update. The
		* driver is not allowed to change anything outside of the free-standing
		* state objects passed-in or assembled in the overall &drm_atomic_state
		* update tracking structure.
		*
		* RETURNS:
		*
		* 0 on success, -EINVAL if the state or the transition can't be
		* supported, -ENOMEM on memory allocation failure and -EDEADLK if an
		* attempt to obtain another state object ran into a &drm_modeset_lock
		* deadlock.
		*/
		int (atomic_check)(struct drm_encoder encoder,
		struct drm_crtc_state *crtc_state,
		struct drm_connector_state *conn_state);
		};

		/**
		* drm_encoder_helper_add - sets the helper vtable for a encoder
		* drm_encoder_helper_add - sets the helper vtable for an encoder
		* @encoder: DRM encoder
		* @funcs: helper vtable to set for @encoder
		*/