This patch clarifies the adjusted_mode documentation
for bridges.

Signed-off-by: Philippe Cornu <philippe.co...@st.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart+rene...@ideasonboard.com>
---
This patch follows discussions in:
- "drm: clarify adjusted_mode for a bridge connected to a crtc"
  https://patchwork.freedesktop.org/patch/206801/
- "drm: bridge: Constify mode arguments to bridge .mode_set() operation"
  https://patchwork.freedesktop.org/patch/215449/

 include/drm/drm_bridge.h | 16 ++++++++++++++++
 include/drm/drm_crtc.h   | 11 +++++++----
 2 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 3270fec46979..7d632c6a9214 100644
--- 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 corresponds to 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 a2d81d2907a9..65f749a9e9d3 100644
--- 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 the 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;
 
-- 
2.15.1

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