On Fri, 03 Jun 2016 00:05:46 +0300
Laurent Pinchart [off-list ref] wrote:

Hi Boris,

Thank you for the patch.

On Thursday 02 Jun 2016 16:31:28 Boris Brezillon wrote:

quoted

Adapt drm_pick_crtcs() and update_connector_routing() to fallback to
drm_atomic_helper_best_encoder() if funcs->best_encoder() is NULL so
that DRM drivers can leave this hook unassigned if they know they want
to use drm_atomic_helper_best_encoder().  

Could you please update include/drm/drm_modeset_helper_vtables.h to document 
this new behaviour ?

Sure.

The only drawback I see in this patch is the additional object lookup 
performed by drm_atomic_helper_best_encoder() at runtime. I wonder if we could 
somehow cache the information, as the assignment can't change when there's a 
1:1 correspondence between encoders and connectors.

quoted

Signed-off-by: Boris Brezillon <redacted>
---
 drivers/gpu/drm/drm_atomic_helper.c |  4 +++-
 drivers/gpu/drm/drm_fb_helper.c     | 13 ++++++++++++-
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c

b/drivers/gpu/drm/drm_atomic_helper.c index f6a3350..849d029 100644

--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c

@@ -300,8 +300,10 @@ update_connector_routing(struct drm_atomic_state

*state, if (funcs->atomic_best_encoder)
 		new_encoder = funcs->atomic_best_encoder(connector,
 							 connector_state);
-	else
+	else if (funcs->best_encoder)
 		new_encoder = funcs->best_encoder(connector);
+	else
+		new_encoder = drm_atomic_helper_best_encoder(connector);

 	if (!new_encoder) {
 		DRM_DEBUG_ATOMIC("No suitable encoder found for [CONNECTOR:%d:%s]\n",

diff --git a/drivers/gpu/drm/drm_fb_helper.c

b/drivers/gpu/drm/drm_fb_helper.c index 7c2eb75..d44389a 100644

--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c

@@ -2000,7 +2000,18 @@ static int drm_pick_crtcs(struct drm_fb_helper

*fb_helper, my_score++;

 	connector_funcs = connector->helper_private;
-	encoder = connector_funcs->best_encoder(connector);
+
+	/*
+	 * If the DRM device implements atomic hooks and ->best_encoder() is
+	 * NULL we fallback to the default drm_atomic_helper_best_encoder()
+	 * helper.
+	 */
+	if (fb_helper->dev->mode_config.funcs->atomic_commit &&
+	    !connector_funcs->best_encoder)
+		encoder = drm_atomic_helper_best_encoder(connector);
+	else
+		encoder = connector_funcs->best_encoder(connector);
+
 	if (!encoder)
 		goto out;  

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com