drm/doc: Document adjusted/request modes a bit better
Laurent started a massive discussion on IRC about this. Let's try to
document common usage a bit better.
v2: Cross-links+typos.
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Jose Abreu <Jose.Abreu@synopsys.com>
Reviewed-by: Jose Abreu <joabreu@synopsys.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170515091136.26307-1-daniel.vetter@ffwll.ch
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index adf4e91..b6e3713 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -90,8 +90,6 @@ struct drm_plane_helper_funcs;
* @plane_mask: bitmask of (1 << drm_plane_index(plane)) of attached planes
* @connector_mask: bitmask of (1 << drm_connector_index(connector)) of attached connectors
* @encoder_mask: bitmask of (1 << drm_encoder_index(encoder)) of attached encoders
- * @adjusted_mode: for use by helpers and drivers to compute adjusted mode timings
- * @mode: current mode timings
* @mode_blob: &drm_property_blob for @mode
* @state: backpointer to global drm_atomic_state
*
@@ -131,9 +129,33 @@ struct drm_crtc_state {
u32 connector_mask;
u32 encoder_mask;
- /* adjusted_mode: for use by helpers and drivers */
+ /**
+ * @adjusted_mode:
+ *
+ * Internal display timings which can be used by the driver to handle
+ * differences between the mode requested by userspace in @mode and what
+ * is actually programmed into the hardware. It is purely driver
+ * implementation defined what exactly this adjusted mode means. Usually
+ * it is used to store the hardware display timings used between the
+ * CRTC and encoder blocks.
+ */
struct drm_display_mode adjusted_mode;
+ /**
+ * @mode:
+ *
+ * Display timings requested by userspace. The driver should try to
+ * match the refresh rate as close as possible (but note that it's
+ * undefined what exactly is close enough, e.g. some of the HDMI modes
+ * only differ in less than 1% of the refresh rate). The active width
+ * and height as observed by userspace for positioning planes must match
+ * exactly.
+ *
+ * For external connectors where the sink isn't fixed (like with a
+ * built-in panel), this mode here should match the physical mode on the
+ * wire to the last details (i.e. including sync polarities and
+ * everything).
+ */
struct drm_display_mode mode;
/* blob property to expose current mode to atomic userspace */