[PATCH RESEND v4 1/4] drm/bridge: Add ->detect_ctx hook and drm_bridge_detect_ctx()

[Cristian Ciocaltea <cristian.ciocaltea@collabora.com>]

Add an atomic variant of the ->detect callback and a new helper to call
the hook while passing an optional drm_modeset_acquire_ctx reference.

When both ->detect_ctx and ->detect are defined, the latter is ignored.
If acquire_ctx is unset, the function takes care of the locking,
while also handling EDEADLK.

Tested-by: Diederik de Haas <diederik@cknow-tech.com>
Tested-by: Maud Spierings <maud_spierings@hotmail.com>
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
---
 drivers/gpu/drm/drm_bridge.c | 58 ++++++++++++++++++++++++++++++++++++++++++++
 include/drm/drm_bridge.h     | 30 +++++++++++++++++++++++
 2 files changed, 88 insertions(+)

diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
index f8b0333a0a3b..1247573c2100 100644
--- a/drivers/gpu/drm/drm_bridge.c
+++ b/drivers/gpu/drm/drm_bridge.c
@@ -1345,6 +1345,64 @@ drm_bridge_detect(struct drm_bridge *bridge, struct drm_connector *connector)
 }
 EXPORT_SYMBOL_GPL(drm_bridge_detect);
 
+/**
+ * drm_bridge_detect_ctx - check if anything is attached to the bridge output
+ * @bridge: bridge control structure
+ * @connector: attached connector
+ * @ctx: acquire_ctx, or NULL to let this function handle locking
+ *
+ * If the bridge supports output detection, as reported by the
+ * DRM_BRIDGE_OP_DETECT bridge ops flag, call &drm_bridge_funcs.detect_ctx
+ * or &drm_bridge_funcs.detect for the bridge and return the connection status.
+ * Otherwise return connector_status_unknown.
+ *
+ * When both @ctx and &drm_bridge_funcs.detect_ctx are not set, this helper
+ * function is equivalent to drm_bridge_detect() above.
+ *
+ * RETURNS:
+ * The detection status on success, or connector_status_unknown if the bridge
+ * doesn't support output detection.
+ * If @ctx is set, it might also return -EDEADLK.
+ */
+int drm_bridge_detect_ctx(struct drm_bridge *bridge,
+			  struct drm_connector *connector,
+			  struct drm_modeset_acquire_ctx *ctx)
+{
+	if (!(bridge->ops & DRM_BRIDGE_OP_DETECT))
+		return connector_status_unknown;
+
+	if (bridge->funcs->detect_ctx) {
+		struct drm_modeset_acquire_ctx br_ctx;
+		int ret;
+
+		if (ctx)
+			return bridge->funcs->detect_ctx(bridge, connector, ctx);
+
+		drm_modeset_acquire_init(&br_ctx, 0);
+retry:
+		ret = drm_modeset_lock(&connector->dev->mode_config.connection_mutex,
+				       &br_ctx);
+		if (!ret)
+			ret = bridge->funcs->detect_ctx(bridge, connector, &br_ctx);
+
+		if (ret == -EDEADLK) {
+			drm_modeset_backoff(&br_ctx);
+			goto retry;
+		}
+
+		if (ret < 0)
+			ret = connector_status_unknown;
+
+		drm_modeset_drop_locks(&br_ctx);
+		drm_modeset_acquire_fini(&br_ctx);
+
+		return ret;
+	}
+
+	return bridge->funcs->detect(bridge, connector);
+}
+EXPORT_SYMBOL_GPL(drm_bridge_detect_ctx);
+
 /**
  * drm_bridge_get_modes - fill all modes currently valid for the sink into the
  * @connector
diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
index 4f19f7064ee3..31ef1496fe63 100644
--- a/include/drm/drm_bridge.h
+++ b/include/drm/drm_bridge.h
@@ -547,6 +547,33 @@ struct drm_bridge_funcs {
 	enum drm_connector_status (*detect)(struct drm_bridge *bridge,
 					    struct drm_connector *connector);
 
+	/**
+	 * @detect_ctx:
+	 *
+	 * Check if anything is attached to the bridge output.
+	 *
+	 * This callback is optional, if not implemented the bridge will be
+	 * considered as always having a component attached to its output.
+	 * Bridges that implement this callback shall set the
+	 * DRM_BRIDGE_OP_DETECT flag in their &drm_bridge->ops.
+	 *
+	 * This is the atomic version of &drm_bridge_funcs.detect.
+	 *
+	 * To avoid races against concurrent connector state updates, the
+	 * helper libraries always call this with ctx set to a valid context,
+	 * and &drm_mode_config.connection_mutex will always be locked with
+	 * the ctx parameter set to this ctx. This allows taking additional
+	 * locks as required.
+	 *
+	 * RETURNS:
+	 *
+	 * &drm_connector_status indicating the bridge output status,
+	 * or the error code returned by drm_modeset_lock(), -EDEADLK.
+	 */
+	int (*detect_ctx)(struct drm_bridge *bridge,
+			  struct drm_connector *connector,
+			  struct drm_modeset_acquire_ctx *ctx);
+
 	/**
 	 * @get_modes:
 	 *
@@ -1542,6 +1569,9 @@ drm_atomic_helper_bridge_propagate_bus_fmt(struct drm_bridge *bridge,
 
 enum drm_connector_status
 drm_bridge_detect(struct drm_bridge *bridge, struct drm_connector *connector);
+int drm_bridge_detect_ctx(struct drm_bridge *bridge,
+			  struct drm_connector *connector,
+			  struct drm_modeset_acquire_ctx *ctx);
 int drm_bridge_get_modes(struct drm_bridge *bridge,
 			 struct drm_connector *connector);
 const struct drm_edid *drm_bridge_edid_read(struct drm_bridge *bridge,

-- 
2.52.0