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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