diff options
Diffstat (limited to 'include/drm/drm_modeset_helper_vtables.h')
| -rw-r--r-- | include/drm/drm_modeset_helper_vtables.h | 159 |
1 files changed, 120 insertions, 39 deletions
diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h index c01c328f6cc8..85984b208218 100644 --- a/include/drm/drm_modeset_helper_vtables.h +++ b/include/drm/drm_modeset_helper_vtables.h @@ -106,6 +106,40 @@ struct drm_crtc_helper_funcs { void (*commit)(struct drm_crtc *crtc); /** + * @mode_valid: + * + * This callback is used to check if a specific mode is valid in this + * crtc. This should be implemented if the crtc has some sort of + * restriction in the modes it can display. For example, a given crtc + * 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(). + * + * This function 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 hardward constraints. Any further + * limits which depend upon the configuration can only be checked in + * @mode_fixup or @atomic_check. + * + * RETURNS: + * + * drm_mode_status Enum + */ + enum drm_mode_status (*mode_valid)(struct drm_crtc *crtc, + const struct drm_display_mode *mode); + + /** * @mode_fixup: * * This callback is used to validate a mode. The parameter mode is the @@ -113,7 +147,8 @@ struct drm_crtc_helper_funcs { * encoders need to be fed with. Note that this is the inverse semantics * of the meaning for the &drm_encoder and &drm_bridge_funcs.mode_fixup * vfunc. If the CRTC cannot support the requested conversion from mode - * to adjusted_mode it should reject the modeset. + * to adjusted_mode it should reject the modeset. See also + * &drm_crtc_state.adjusted_mode for more details. * * This function is used by both legacy CRTC helpers and atomic helpers. * With atomic helpers it is optional. @@ -130,22 +165,17 @@ struct drm_crtc_helper_funcs { * allowed. * * Atomic drivers which need to inspect and adjust more state should - * instead use the @atomic_check callback. - * - * Also beware that neither core nor helpers filter modes before - * passing them to the driver: While the list of modes that is - * advertised to userspace is filtered using the - * &drm_connector.mode_valid callback, neither the core nor the helpers - * do any filtering on modes passed in from userspace when setting a - * mode. It is therefore possible for userspace to pass in a mode that - * was previously filtered out using &drm_connector.mode_valid or add a - * custom mode that wasn't probed from EDID or similar to begin with. - * Even though this is an advanced feature and rarely used nowadays, - * some users rely on being able to specify modes manually so drivers - * must be prepared to deal with it. Specifically this means that all - * drivers need not only validate modes in &drm_connector.mode_valid but - * also in this or in the &drm_encoder_helper_funcs.mode_fixup callback - * to make sure invalid modes passed in from userspace are rejected. + * instead use the @atomic_check callback, but note that they're not + * perfectly equivalent: @mode_valid is called from + * drm_atomic_helper_check_modeset(), but @atomic_check is called from + * drm_atomic_helper_check_planes(), because originally it was meant for + * plane update checks only. + * + * 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 CRTC constraints and + * limits checks into @mode_valid. * * RETURNS: * @@ -341,6 +371,12 @@ struct drm_crtc_helper_funcs { * state objects passed-in or assembled in the overall &drm_atomic_state * update tracking structure. * + * 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 CRTC constraints and + * limits checks into @mode_valid. + * * RETURNS: * * 0 on success, -EINVAL if the state or the transition can't be @@ -457,13 +493,48 @@ struct drm_encoder_helper_funcs { void (*dpms)(struct drm_encoder *encoder, int mode); /** + * @mode_valid: + * + * This callback is used to check if a specific mode is valid in this + * encoder. This should be implemented if the encoder has some sort + * of restriction in the modes it can display. For example, a given + * encoder 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(). + * + * This function 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 hardward constraints. Any further + * limits which depend upon the configuration can only be checked in + * @mode_fixup or @atomic_check. + * + * RETURNS: + * + * drm_mode_status Enum + */ + enum drm_mode_status (*mode_valid)(struct drm_encoder *crtc, + 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 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. + * can be modified by this callback and does not need to match mode. See + * also &drm_crtc_state.adjusted_mode for more details. * * This function is used by both legacy CRTC helpers and atomic helpers. * This hook is optional. @@ -480,23 +551,15 @@ struct drm_encoder_helper_funcs { * allowed. * * Atomic drivers which need to inspect and adjust more state should - * instead use the @atomic_check callback. - * - * Also beware that neither core nor helpers filter modes before - * passing them to the driver: While the list of modes that is - * advertised to userspace is filtered using the connector's - * &drm_connector_helper_funcs.mode_valid callback, neither the core nor - * the helpers do any filtering on modes passed in from userspace when - * setting a mode. It is therefore possible for userspace to pass in a - * mode that was previously filtered out using - * &drm_connector_helper_funcs.mode_valid or add a custom mode that - * wasn't probed from EDID or similar to begin with. Even though this - * is an advanced feature and rarely used nowadays, some users rely on - * being able to specify modes manually so drivers must be prepared to - * deal with it. Specifically this means that all drivers need not only - * validate modes in &drm_connector.mode_valid but also in this or in - * the &drm_crtc_helper_funcs.mode_fixup callback to make sure - * invalid modes passed in from userspace are rejected. + * instead use the @atomic_check callback. If @atomic_check is used, + * this hook isn't called since @atomic_check allows a strict superset + * of the functionality of @mode_fixup. + * + * 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 encoder constraints and + * limits checks into @mode_valid. * * RETURNS: * @@ -677,6 +740,11 @@ struct drm_encoder_helper_funcs { * update the CRTC to match what the encoder needs for the requested * connector. * + * Since this provides a strict superset of the functionality of + * @mode_fixup (the requested and adjusted modes are both available + * through the passed in &struct drm_crtc_state) @mode_fixup is not + * called when @atomic_check is implemented. + * * This function is used by the atomic helpers, but it is optional. * * NOTE: @@ -686,6 +754,12 @@ struct drm_encoder_helper_funcs { * state objects passed-in or assembled in the overall &drm_atomic_state * update tracking structure. * + * 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 encoder constraints and + * limits checks into @mode_valid. + * * RETURNS: * * 0 on success, -EINVAL if the state or the transition can't be @@ -795,13 +869,20 @@ struct drm_connector_helper_funcs { * (which is usually derived from the EDID data block from the sink). * See e.g. drm_helper_probe_single_connector_modes(). * + * This function is optional. + * * 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. + * GETCONNECTOR IOCTL. Compared to &drm_encoder_helper_funcs.mode_valid, + * &drm_crtc_helper_funcs.mode_valid and &drm_bridge_funcs.mode_valid, + * which are also called by the atomic helpers from + * drm_atomic_helper_check_modeset(). This allows userspace to force and + * ignore sink constraint (like the pixel clock limits in the screen's + * EDID), which is useful for e.g. testing, or working around a broken + * EDID. Any source hardware constraint (which always need to be + * enforced) therefore should be checked in one of the above callbacks, + * and not this one here. * * To avoid races with concurrent connector state updates, the helper * libraries always call this with the &drm_mode_config.connection_mutex |