[PATCH RFC 12/19] drm/bridge: Add an ->atomic_check() hook

[Boris Brezillon]

So that bridge drivers have a way to check/reject an atomic operation.
The drm_atomic_bridge_chain_check() (which is just a wrapper around
the ->atomic_check() hook) is called in place of
drm_bridge_chain_mode_fixup() (when ->atomic_check() is not implemented,
the core falls back to ->mode_fixup(), so the behavior should stay
the same for existing bridge drivers).

Signed-off-by: Boris Brezillon <boris.brezillon at collabora.com>
---
 drivers/gpu/drm/drm_atomic_helper.c | 11 +++---
 drivers/gpu/drm/drm_bridge.c        | 59 +++++++++++++++++++++++++++++
 include/drm/drm_bridge.h            | 23 +++++++++++
 3 files changed, 87 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index e76ec9648b6f..3fadde38ead7 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -445,12 +445,11 @@ mode_fixup(struct drm_atomic_state *state)
 		encoder = new_conn_state->best_encoder;
 		funcs = encoder->helper_private;
 
-		ret = drm_bridge_chain_mode_fixup(encoder,
-					&new_crtc_state->mode,
-					&new_crtc_state->adjusted_mode);
-		if (!ret) {
-			DRM_DEBUG_ATOMIC("Bridge fixup failed\n");
-			return -EINVAL;
+		ret = drm_atomic_bridge_chain_check(encoder, new_crtc_state,
+						    new_conn_state);
+		if (ret) {
+			DRM_DEBUG_ATOMIC("Bridge atomic check failed\n");
+			return ret;
 		}
 
 		if (funcs && funcs->atomic_check) {
diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index 0528ca941855..dcad661daa74 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -583,6 +583,65 @@ void drm_atomic_bridge_chain_enable(struct drm_encoder *encoder,
 }
 EXPORT_SYMBOL(drm_atomic_bridge_chain_enable);
 
+static int drm_atomic_bridge_check(struct drm_bridge *bridge,
+				   struct drm_crtc_state *crtc_state,
+				   struct drm_connector_state *conn_state)
+{
+	if (bridge->funcs->atomic_check) {
+		struct drm_bridge_state *bridge_state;
+		int ret;
+
+		bridge_state = drm_atomic_get_new_bridge_state(crtc_state->state,
+							       bridge);
+		if (WARN_ON(!bridge_state))
+			return -EINVAL;
+
+		ret = bridge->funcs->atomic_check(bridge, bridge_state,
+						  crtc_state, conn_state);
+		if (ret)
+			return ret;
+	} else if (bridge->funcs->mode_fixup) {
+		if (!bridge->funcs->mode_fixup(bridge, &crtc_state->mode,
+					       &crtc_state->adjusted_mode))
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
+/**
+ * drm_atomic_bridge_chain_check() - Do an atomic check on the bridge chain
+ * @encoder: encoder object
+ * @crtc_state: new CRTC state
+ * @conn_state: new connector state
+ *
+ * Calls &drm_bridge_funcs.atomic_check() (falls back on
+ * &drm_bridge_funcs.mode_fixup()) op for all the bridges in the encoder chain,
+ * starting from the last bridge to the first. These are called before calling
+ * &drm_encoder_helper_funcs.atomic_check()
+ *
+ * RETURNS:
+ * 0 on success, a negative error code on failure
+ */
+int drm_atomic_bridge_chain_check(struct drm_encoder *encoder,
+				  struct drm_crtc_state *crtc_state,
+				  struct drm_connector_state *conn_state)
+{
+	struct drm_bridge *bridge;
+
+	list_for_each_entry_reverse(bridge, &encoder->bridge_chain,
+				    chain_node) {
+		int ret;
+
+		ret = drm_atomic_bridge_check(bridge, crtc_state, conn_state);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_atomic_bridge_chain_check);
+
 /**
  * drm_atomic_helper_init_bridge_state() - Initializes a bridge state
  * @bridge this state is referring to
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 9383b4e4b853..5d8fe3709bde 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -379,6 +379,26 @@ struct drm_bridge_funcs {
 	 */
 	void (*atomic_destroy_state)(struct drm_bridge *bridge,
 				     struct drm_bridge_state *state);
+
+	/**
+	 * @atomic_check:
+	 *
+	 * This method is responsible for checking bridge state correctness.
+	 * It can also check the state of the surrounding components in chain
+	 * to make sure the whole pipeline can work properly.
+	 *
+	 * &drm_bridge_funcs.atomic_check() hooks are called in reverse
+	 * order (from the last to the first bridge).
+	 *
+	 * This method is optional.
+	 *
+	 * RETURNS:
+	 * zero if the check passed, a negative error code otherwise.
+	 */
+	int (*atomic_check)(struct drm_bridge *bridge,
+			    struct drm_bridge_state *bridge_state,
+			    struct drm_crtc_state *crtc_state,
+			    struct drm_connector_state *conn_state);
 };
 
 /**
@@ -479,6 +499,9 @@ void drm_bridge_chain_mode_set(struct drm_encoder *encoder,
 void drm_bridge_chain_pre_enable(struct drm_encoder *encoder);
 void drm_bridge_chain_enable(struct drm_encoder *encoder);
 
+int drm_atomic_bridge_chain_check(struct drm_encoder *encoder,
+				  struct drm_crtc_state *crtc_state,
+				  struct drm_connector_state *conn_state);
 void drm_atomic_bridge_chain_disable(struct drm_encoder *encoder,
 				     struct drm_atomic_state *state);
 void drm_atomic_bridge_chain_post_disable(struct drm_encoder *encoder,
-- 
2.21.0