[PATCH 23/28] drm: Document drm_plane_helper_funcs

Daniel Vetter
2015-12-04T08:46:04Z

Plus related hooks used to do atomic plane updates since they only
really make sense as a package.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
include/drm/drm_modeset_helper_vtables.h | 209 +++++++++++++++++++++++++++++--
1 file changed, 198 insertions(+), 11 deletions(-)

diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
index bc731754fc70..66b78c14154e 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -57,9 +57,6 @@ enum mode_set_atomic;
* @load_lut: load color palette
* @disable: disable CRTC when no longer in use
* @enable: enable CRTC
- * @atomic_check: check for validity of an atomic state
- * @atomic_begin: begin atomic update
- * @atomic_flush: flush atomic update
*
* The helper operations are called by the mid-layer CRTC helper.
*
@@ -103,11 +100,95 @@ struct drm_crtc_helper_funcs {
void (*disable)(struct drm_crtc *crtc);
void (*enable)(struct drm_crtc *crtc);

- /* atomic helpers */
+ /**
+ * @atomic_check:
+ *
+ * Drivers should check plane-update related CRTC constraints in this
+ * hook. They can also check mode related limitations but need to be
+ * aware of the calling order, since this hook is used by
+ * drm_atomic_helper_check_planes() whereas the prepartions needed to
+ * check output routing and the display mode is done in
+ * drm_atomic_helper_check_modeset(). Therefore drivers who want to
+ * check output routing and display mode contstraints in this callback
+ * mus ensure that drm_atomic_helper_check_modeset() has been called
+ * beforehand.
+ *
+ * When using drm_atomic_helper_check_planes CRTC's ->atomic_check()
+ * hooks are called after the ones for palnes, which allows drivers to
+ * assign shared resources requested by planes in the CRTC callback
+ * here. For more complicated depencies the driver can call the provided
+ * check helpers multiple times until the computed state has a final
+ * configuration and everything has been checked.
+ *
+ * This function is also allowed to inspect any other object's state and
+ * can add more state objects to the atomic commit if needed. Care must
+ * be taken though to ensure that state check&compute functions for
+ * these added states are all called, and derived state in other objects
+ * all updated. Again the recommendation is to just call check helpers
+ * until a maximal configuration is reached.
+ *
+ * This callback is used by the atomic modeset helpers and by the
+ * transitional plane 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
+ * support, -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_crtc *crtc,
struct drm_crtc_state *state);
+
+ /**
+ * @atomic_begin:
+ *
+ * Drivers should prepare for an atomic update of multiple planes on
+ * a CRTC in this hook. Depending upon hardware this might be vblank
+ * evasion, blocking updates by setting bits or doing prepatory work for
+ * e.g. manual update display.
+ *
+ * This hook is called before any plane commit functions are called.
+ *
+ * Note that the power state of the display pipe when this function is
+ * called depends upon the exact helpers and calling sequence the driver
+ * has picked. See drm_atomic_commit_planes for a discussion of the
+ * tradeoffs and variants of plane commit helpers.
+ *
+ * This callback is used by the atomic modeset helpers and by the
+ * transitional plane helpers, but it is optional.
+ */
void (*atomic_begin)(struct drm_crtc *crtc,
struct drm_crtc_state *old_crtc_state);
+ /**
+ * @atomic_flush:
+ *
+ * Drivers should prepare for an atomic update of multiple planes on
+ * a CRTC in this hook. Depending upon hardware this might include
+ * checking that vblank evasion was successful, unblocking updates by
+ * setting bits or setting the GO bit to flush out all updates.
+ *
+ * Simple hardware or hardware with special requirements can commit and
+ * flush out all updates for all planes from this hook and forgo all the
+ * other commit hooks for plane updates.
+ *
+ * This hook is called after any plane commit functions are called.
+ *
+ * Note that the power state of the display pipe when this function is
+ * called depends upon the exact helpers and calling sequence the driver
+ * has picked. See drm_atomic_commit_planes for a discussion of the
+ * tradeoffs and variants of plane commit helpers.
+ *
+ * This callback is used by the atomic modeset helpers and by the
+ * transitional plane helpers, but it is optional.
+ */
void (*atomic_flush)(struct drm_crtc *crtc,
struct drm_crtc_state *old_crtc_state);
};
@@ -211,25 +292,131 @@ static inline void drm_connector_helper_add(struct drm_connector *connector,
}

/**
- * struct drm_plane_helper_funcs - helper operations for CRTCs
- * @prepare_fb: prepare a framebuffer for use by the plane
- * @cleanup_fb: cleanup a framebuffer when it's no longer used by the plane
- * @atomic_check: check that a given atomic state is valid and can be applied
- * @atomic_update: apply an atomic state to the plane (mandatory)
- * @atomic_disable: disable the plane
+ * struct drm_plane_helper_funcs - helper operations for planes
*
- * The helper operations are called by the mid-layer CRTC helper.
+ * These functions are used by the atomic helpers and by the transitional plane
+ * helpers.
*/
struct drm_plane_helper_funcs {
+ /**
+ * @prepare_fb:
+ *
+ * This hook is to prepare a framebuffer for scanout by e.g. pinning
+ * it's backing storage or relocating it into a contiguous block of
+ * vram. Other possible preparatory work includes flushing caches.
+ *
+ * This function must not block for outstanding rendering, since it is
+ * called in the context of the atomic IOCTL even for async commits to
+ * be able to return any errors to userspace. Instead the recommended
+ * why is to fill out the fence member of the passed-in
+ * &drm_plane_state. If the driver doesn't support native fences then
+ * equivalent functionality should be implemented through private
+ * members in the plane structure.
+ *
+ * The helpers will call @cleanup_fb with matching arguments for every
+ * successful call to this hook.
+ *
+ * This callback is used by the atomic modeset helpers and by the
+ * transitional plane helpers, but it is optional.
+ *
+ * RETURNS:
+ *
+ * 0 on sucess or one of the following negative error codes allowed by
+ * the atomic_commit hook in &drm_mode_config_funcs. When using helpers
+ * this callback is the only one which can fail an atomic commit,
+ * everything else must complete successfully.
+ */
int (*prepare_fb)(struct drm_plane *plane,
const struct drm_plane_state *new_state);
+ /**
+ * @cleanup_fb:
+ *
+ * This hook is called to clean up any resources allocated for the given
+ * framebuffer and plane configuration in @prepare_fb.
+ *
+ * This callback is used by the atomic modeset helpers and by the
+ * transitional plane helpers, but it is optional.
+ */
void (*cleanup_fb)(struct drm_plane *plane,
const struct drm_plane_state *old_state);

+ /**
+ * @atomic_check:
+ *
+ * Drivers should check plane specific constraints in this hook.
+ *
+ * When using drm_atomic_helper_check_planes plane's ->atomic_check()
+ * hooks are called before the ones for CRTCs, which allows drivers to
+ * request shared resources that the CRTC controls here. For more
+ * complicated depencies the driver can call the provided check helpers
+ * multiple times until the computed state has a final configuration and
+ * everything has been checked.
+ *
+ * This function is also allowed to inspect any other object's state and
+ * can add more state objects to the atomic commit if needed. Care must
+ * be taken though to ensure that state check&compute functions for
+ * these added states are all called, and derived state in other objects
+ * all updated. Again the recommendation is to just call check helpers
+ * until a maximal configuration is reached.
+ *
+ * This callback is used by the atomic modeset helpers and by the
+ * transitional plane 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
+ * support, -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_plane *plane,
struct drm_plane_state *state);
+
+ /**
+ * @atomic_update:
+ *
+ * Drivers should use this function to update the plane state. This
+ * hook is called in-between the ->atomic_begin and
+ * ->atomic_flush() of &drm_crtc_helper_funcs.
+ *
+ * Note that the power state of the display pipe when this function is
+ * called depends upon the exact helpers and calling sequence the driver
+ * has picked. See drm_atomic_commit_planes for a discussion of the
+ * tradeoffs and variants of plane commit helpers.
+ *
+ * This callback is used by the atomic modeset helpers and by the
+ * transitional plane helpers, but it is optional.
+ */
void (*atomic_update)(struct drm_plane *plane,
struct drm_plane_state *old_state);
+ /**
+ * @atomic_disable:
+ *
+ * Drivers should use this function to unconditionally disable a plane.
+ * This hook is called in-between the ->atomic_begin and
+ * ->atomic_flush() of &drm_crtc_helper_funcs. It is an alternative to
+ * @atomic_update, which will be called for disabling planes, too, if
+ * the @atomic_disable hook isn't implemented.
+ *
+ * This hook is also useful to disable planes in preration of a modeset,
+ * by calling drm_atomic_helper_disable_planes_on_crtc() from the
+ * ->disable hook in &drm_crtc_helper_funcs.
+ *
+ * Note that the power state of the display pipe when this function is
+ * called depends upon the exact helpers and calling sequence the driver
+ * has picked. See drm_atomic_commit_planes for a discussion of the
+ * tradeoffs and variants of plane commit helpers.
+ *
+ * This callback is used by the atomic modeset helpers and by the
+ * transitional plane helpers, but it is optional.
+ */
void (*atomic_disable)(struct drm_plane *plane,
struct drm_plane_state *old_state);
};
--
2.5.1

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