drm: clarify adjusted_mode documentation for bridges

This patch clarifies the adjusted_mode documentation
for bridges.

Signed-off-by: Philippe Cornu <philippe.cornu@st.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Archit Taneja <architt@codeaurora.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20180409152427.12449-1-philippe.cornu@st.com

diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 3270fec..9917651 100644 (file)
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -178,6 +178,22 @@ struct drm_bridge_funcs {
         * then this would be &drm_encoder_helper_funcs.mode_set. The display
         * pipe (i.e.  clocks and timing signals) is off when this function is
         * called.
+        *
+        * The adjusted_mode parameter is the mode output by the CRTC for the
+        * first bridge in the chain. It can be different from the mode
+        * parameter that contains the desired mode for the connector at the end
+        * of the bridges chain, for instance when the first bridge in the chain
+        * performs scaling. The adjusted mode is mostly useful for the first
+        * bridge in the chain and is likely irrelevant for the other bridges.
+        *
+        * For atomic drivers the adjusted_mode is the mode stored in
+        * &drm_crtc_state.adjusted_mode.
+        *
+        * NOTE:
+        *
+        * If a need arises to store and access modes adjusted for other
+        * locations than the connection between the CRTC and the first bridge,
+        * the DRM framework will have to be extended with DRM bridge states.
         */
        void (*mode_set)(struct drm_bridge *bridge,
                         struct drm_display_mode *mode,

diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index a2d81d2..5cf7ade 100644 (file)
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -134,10 +134,13 @@ struct drm_crtc_state {
         *
         * 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.
+        * is actually programmed into the hardware.
+        *
+        * For drivers using drm_bridge, this stores hardware display timings
+        * used between the CRTC and the first bridge. For other drivers, the
+        * meaning of the adjusted_mode field is purely driver implementation
+        * defined information, and will usually be used to store the hardware
+        * display timings used between the CRTC and encoder blocks.
         */
        struct drm_display_mode adjusted_mode;