[PATCH v4] drm/sysfs: Link DRM connectors to corresponding Type-C connectors

[Won Chung <wonchung@google.com>]

Create a symlink pointing to USB Type-C connector for DRM connectors
when they are created. The link will be created only if the firmware is
able to describe the connection beween the two connectors.

Currently, even if a display uses a USB Type-C port, there is no way for
the userspace to find which port is used for which display. With the
symlink, display information would be accessible from Type-C connectors
and port information would be accessible from DRM connectors.
Associating the two subsystems, userspace would have potential to expose
and utilize more complex information, such as bandwidth used for a
specific USB Type-C port.

Signed-off-by: Won Chung <wonchung@google.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
---
Changes from v3:
- Append to the commit message on why this patch is needed

Changes from v2:
- Resend the patch to dri-devel list

Changes from v1:
- Fix multiple lines to single line


 drivers/gpu/drm/drm_sysfs.c | 40 +++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/drivers/gpu/drm/drm_sysfs.c b/drivers/gpu/drm/drm_sysfs.c
index 430e00b16eec..6a9904fa9186 100644
--- a/drivers/gpu/drm/drm_sysfs.c
+++ b/drivers/gpu/drm/drm_sysfs.c
@@ -11,12 +11,14 @@
  */
 
 #include <linux/acpi.h>
+#include <linux/component.h>
 #include <linux/device.h>
 #include <linux/err.h>
 #include <linux/export.h>
 #include <linux/gfp.h>
 #include <linux/i2c.h>
 #include <linux/kdev_t.h>
+#include <linux/property.h>
 #include <linux/slab.h>
 
 #include <drm/drm_connector.h>
@@ -95,6 +97,34 @@ static char *drm_devnode(struct device *dev, umode_t *mode)
 	return kasprintf(GFP_KERNEL, "dri/%s", dev_name(dev));
 }
 
+static int typec_connector_bind(struct device *dev,
+	struct device *typec_connector, void *data)
+{
+	int ret;
+
+	ret = sysfs_create_link(&dev->kobj, &typec_connector->kobj, "typec_connector");
+	if (ret)
+		return ret;
+
+	ret = sysfs_create_link(&typec_connector->kobj, &dev->kobj, "drm_connector");
+	if (ret)
+		sysfs_remove_link(&dev->kobj, "typec_connector");
+
+	return ret;
+}
+
+static void typec_connector_unbind(struct device *dev,
+	struct device *typec_connector, void *data)
+{
+	sysfs_remove_link(&typec_connector->kobj, "drm_connector");
+	sysfs_remove_link(&dev->kobj, "typec_connector");
+}
+
+static const struct component_ops typec_connector_ops = {
+	.bind = typec_connector_bind,
+	.unbind = typec_connector_unbind,
+};
+
 static CLASS_ATTR_STRING(version, S_IRUGO, "drm 1.1.0 20060810");
 
 /**
@@ -355,6 +385,13 @@ int drm_sysfs_connector_add(struct drm_connector *connector)
 	if (connector->ddc)
 		return sysfs_create_link(&connector->kdev->kobj,
 				 &connector->ddc->dev.kobj, "ddc");
+
+	if (dev_fwnode(kdev)) {
+		r = component_add(kdev, &typec_connector_ops);
+		if (r)
+			drm_err(dev, "failed to add component\n");
+	}
+
 	return 0;
 
 err_free:
@@ -367,6 +404,9 @@ void drm_sysfs_connector_remove(struct drm_connector *connector)
 	if (!connector->kdev)
 		return;
 
+	if (dev_fwnode(connector->kdev))
+		component_del(connector->kdev, &typec_connector_ops);
+
 	if (connector->ddc)
 		sysfs_remove_link(&connector->kdev->kobj, "ddc");
 
-- 
2.37.3.998.g577e59143f-goog