drm/bridge: Add an ->atomic_check() hook

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 on ->mode_fixup(), so the behavior should stay
the same for existing bridge drivers).

v10:
* Add changelog to the commit message

v8 -> v9:
* No changes

v7:
* Fix a NULL pointer dereference

v5 -> v6:
* No changes

v4:
* Add R-bs

v3:
* No changes

v2:
* Clarify the fact that ->atomic_check() is replacing ->mode_fixup()

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed by: Jernej Skrabec <jernej.skrabec@siol.net>
Tested-by: Jonas Karlman <jonas@kwiboo.se>
Link: https://patchwork.freedesktop.org/patch/msgid/20200128135514.108171-6-boris.brezillon@collabora.com

1 files changed, 66 insertions, 0 deletions

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index f6206e655da4..c8beb1385771 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -602,6 +602,72 @@ void drm_atomic_bridge_chain_enable(struct drm_bridge *bridge,
 }
 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
+ * @bridge: bridge control structure
+ * @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_bridge *bridge,
+				  struct drm_crtc_state *crtc_state,
+				  struct drm_connector_state *conn_state)
+{
+	struct drm_encoder *encoder;
+	struct drm_bridge *iter;
+
+	if (!bridge)
+		return 0;
+
+	encoder = bridge->encoder;
+	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
+		int ret;
+
+		ret = drm_atomic_bridge_check(iter, crtc_state, conn_state);
+		if (ret)
+			return ret;
+
+		if (iter == bridge)
+			break;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(drm_atomic_bridge_chain_check);
+
 #ifdef CONFIG_OF
 /**
  * of_drm_find_bridge - find the bridge corresponding to the device node in