[PATCH v2 01/20] drm/atomic: Fix remaining places where !funcs->best_encoder is valid

[Boris Brezillon]

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().

Update the vtables documentation accordingly.

Signed-off-by: Boris Brezillon <boris.brezillon at free-electrons.com>
---
 drivers/gpu/drm/drm_atomic_helper.c      |  4 +++-
 drivers/gpu/drm/drm_fb_helper.c          | 13 ++++++++++++-
 include/drm/drm_modeset_helper_vtables.h | 10 ++++++++--
 3 files changed, 23 insertions(+), 4 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;
 
diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h
index d4619dc..4e7a53b 100644
--- a/include/drm/drm_modeset_helper_vtables.h
+++ b/include/drm/drm_modeset_helper_vtables.h
@@ -736,6 +736,11 @@ struct drm_connector_helper_funcs {
 	 * inspect dynamic configuration state should instead use
 	 * @atomic_best_encoder.
 	 *
+	 * You can leave this function to NULL if the connector is only
+	 * attached to a single encoder and you are using the atomic helpers.
+	 * In this case, the core will call drm_atomic_helper_best_encoder()
+	 * for you.
+	 *
 	 * RETURNS:
 	 *
 	 * Encoder that should be used for the given connector and connector
@@ -752,8 +757,9 @@ struct drm_connector_helper_funcs {
 	 * need to select the best encoder depending upon the desired
 	 * configuration and can't select it statically.
 	 *
-	 * This function is used by drm_atomic_helper_check_modeset() and either
-	 * this or @best_encoder is required.
+	 * This function is used by drm_atomic_helper_check_modeset().
+	 * If it is not implemented, the core will fallback to @best_encoder
+	 * (or drm_atomic_helper_best_encoder() if @best_encoder is NULL).
 	 *
 	 * NOTE:
 	 *
-- 
2.7.4