drm: Document drm_connector_helper_funcs
Nothing special, except the somewhat awkward split in probe helper
callbacks between here and drm_crtc_funcs.
v2: Suggestions from Thierry.
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1449218769-16577-25-git-send-email-daniel.vetter@ffwll.ch
Reviewed-by: Thierry Reding <treding@nvidia.com>
diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
index c77b7dc..4b3869b 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -270,18 +270,114 @@
/**
* struct drm_connector_helper_funcs - helper operations for connectors
- * @get_modes: get mode list for this connector
- * @mode_valid: is this mode valid on the given connector? (optional)
- * @best_encoder: return the preferred encoder for this connector
- * @atomic_best_encoder: atomic version of @best_encoder
*
- * The helper operations are called by the mid-layer CRTC helper.
+ * These functions are used by the atomic and legacy modeset helpers and by the
+ * probe helpers.
*/
struct drm_connector_helper_funcs {
+ /**
+ * @get_modes:
+ *
+ * This function should fill in all modes currently valid for the sink
+ * into the connector->probed_modes list. It should also update the
+ * EDID property by calling drm_mode_connector_update_edid_property().
+ *
+ * The usual way to implement this is to cache the EDID retrieved in the
+ * probe callback somewhere in the driver-private connector structure.
+ * In this function drivers then parse the modes in the EDID and add
+ * them by calling drm_add_edid_modes(). But connectors that driver a
+ * fixed panel can also manually add specific modes using
+ * drm_mode_probed_add(). Finally drivers that support audio probably
+ * want to update the ELD data, too, using drm_edid_to_eld().
+ *
+ * This function is only called after the ->detect() hook has indicated
+ * that a sink is connected and when the EDID isn't overridden through
+ * sysfs or the kernel commandline.
+ *
+ * This callback is used by the probe helpers in e.g.
+ * drm_helper_probe_single_connector_modes().
+ *
+ * RETURNS:
+ *
+ * The number of modes added by calling drm_mode_probed_add().
+ */
int (*get_modes)(struct drm_connector *connector);
+
+ /**
+ * @mode_valid:
+ *
+ * Callback to validate a mode for a connector, irrespective of the
+ * specific display configuration.
+ *
+ * This callback is used by the probe helpers to filter the mode list
+ * (which is usually derived from the EDID data block from the sink).
+ * See e.g. drm_helper_probe_single_connector_modes().
+ *
+ * NOTE:
+ *
+ * This only filters the mode list supplied to userspace in the
+ * GETCONNECOTR IOCTL. Userspace is free to create modes of its own and
+ * ask the kernel to use them. It this case the atomic helpers or legacy
+ * CRTC helpers will not call this function. Drivers therefore must
+ * still fully validate any mode passed in in a modeset request.
+ *
+ * RETURNS:
+ *
+ * Either MODE_OK or one of the failure reasons in enum
+ * &drm_mode_status.
+ */
enum drm_mode_status (*mode_valid)(struct drm_connector *connector,
struct drm_display_mode *mode);
+ /**
+ * @best_encoder:
+ *
+ * This function should select the best encoder for the given connector.
+ *
+ * This function is used by both the atomic helpers (in the
+ * drm_atomic_helper_check_modeset() function) and in the legacy CRTC
+ * helpers.
+ *
+ * NOTE:
+ *
+ * In atomic drivers this function is called in the check phase of an
+ * atomic update. The driver is not allowed to change or inspect
+ * anything outside of arguments passed-in. Atomic drivers which need to
+ * inspect dynamic configuration state should instead use
+ * @atomic_best_encoder.
+ *
+ * RETURNS:
+ *
+ * Encoder that should be used for the given connector and connector
+ * state, or NULL if no suitable encoder exists. Note that the helpers
+ * will ensure that encoders aren't used twice, drivers should not check
+ * for this.
+ */
struct drm_encoder *(*best_encoder)(struct drm_connector *connector);
+
+ /**
+ * @atomic_best_encoder:
+ *
+ * This is the atomic version of @best_encoder for atomic drivers which
+ * need to select the best encoder depending upon the desired
+ * configuration and can't select it statically.
+ *
+ * This function is used by drm_atomic_helper_check_modeset() and either
+ * this or @best_encoder is required.
+ *
+ * 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:
+ *
+ * Encoder that should be used for the given connector and connector
+ * state, or NULL if no suitable encoder exists. Note that the helpers
+ * will ensure that encoders aren't used twice, drivers should not check
+ * for this.
+ */
struct drm_encoder *(*atomic_best_encoder)(struct drm_connector *connector,
struct drm_connector_state *connector_state);
};