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* [PATCH] drm: clarify adjusted_mode documentation for bridges
@ 2018-04-09 15:24 Philippe Cornu
  2018-04-19 15:50 ` Philippe CORNU
  0 siblings, 1 reply; 4+ messages in thread
From: Philippe Cornu @ 2018-04-09 15:24 UTC (permalink / raw)
  To: Laurent Pinchart, Daniel Vetter, Gustavo Padovan,
	Maarten Lankhorst, Sean Paul, David Airlie, dri-devel,
	linux-kernel
  Cc: Benjamin Gaignard, Yannick Fertre, Philippe Cornu, Vincent Abriou

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>
---
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

^ permalink raw reply	[flat|nested] 4+ messages in thread

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Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2018-04-09 15:24 [PATCH] drm: clarify adjusted_mode documentation for bridges Philippe Cornu
2018-04-19 15:50 ` Philippe CORNU
2018-04-19 17:00   ` Archit Taneja
2018-05-15 15:47     ` Philippe CORNU

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