From 9f800214731fddb0a99810bcd1af8d93d22076e0 Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Mon, 15 May 2017 11:11:36 +0200 Subject: [PATCH] drm/doc: Clarify mode_fixup vs. atomic_check a bit more Brought up by both Laurent and Andrzej when reviewing the new ->mode_valid hooks. Since mode_fixup is just a simpler version of the much more generic atomic_check we can't really unify it with mode_valid. Most drivers should probably switch their current mode_fixup code to either the new mode_valid or the atomic_check hooks, but e.g. that doesn't exist yet for bridges, and for CRTCs the situation is a bit more complicated. Hence there's no clear equivalence between mode_fixup and mode_valid, even if it looks like that at first glance. v2: Fix accidental double-dot (Adnrzej). Cc: Andrzej Hajda Cc: Laurent Pinchart Cc: Jose Abreu Reviewed-by: Jose Abreu Reviewed-by: Andrzej Hajda Signed-off-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/20170515091136.26307-2-daniel.vetter@ffwll.ch --- include/drm/drm_modeset_helper_vtables.h | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h index 361240ca738e..85984b208218 100644 --- a/include/drm/drm_modeset_helper_vtables.h +++ b/include/drm/drm_modeset_helper_vtables.h @@ -165,7 +165,11 @@ struct drm_crtc_helper_funcs { * allowed. * * Atomic drivers which need to inspect and adjust more state should - * instead use the @atomic_check callback. + * 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 @@ -547,7 +551,9 @@ struct drm_encoder_helper_funcs { * allowed. * * Atomic drivers which need to inspect and adjust more state should - * instead use the @atomic_check callback. + * 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 @@ -734,6 +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: -- 2.20.1