1 files changed, 86 insertions, 20 deletions

diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 6dbb98649795..a525751b4559 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -303,9 +303,10 @@ void drm_minor_release(struct drm_minor *minor)
  * callbacks implemented by the driver. The driver then needs to initialize all
  * the various subsystems for the drm device like memory management, vblank
  * handling, modesetting support and intial output configuration plus obviously
- * initialize all the corresponding hardware bits. Finally when everything is up
- * and running and ready for userspace the device instance can be published
- * using drm_dev_register().
+ * initialize all the corresponding hardware bits. An important part of this is
+ * also calling drm_dev_set_unique() to set the userspace-visible unique name of
+ * this device instance. Finally when everything is up and running and ready for
+ * userspace the device instance can be published using drm_dev_register().
  *
  * There is also deprecated support for initalizing device instances using
  * bus-specific helpers and the ->load() callback. But due to
@@ -327,17 +328,6 @@ void drm_minor_release(struct drm_minor *minor)
  * dev_priv field of &drm_device.
  */
 
-static int drm_dev_set_unique(struct drm_device *dev, const char *name)
-{
-	if (!name)
-		return -EINVAL;
-
-	kfree(dev->unique);
-	dev->unique = kstrdup(name, GFP_KERNEL);
-
-	return dev->unique ? 0 : -ENOMEM;
-}
-
 /**
  * drm_put_dev - Unregister and release a DRM device
  * @dev: DRM device
@@ -507,12 +497,6 @@ int drm_dev_init(struct drm_device *dev,
 		goto err_free;
 	}
 
-	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
-		ret = drm_minor_alloc(dev, DRM_MINOR_CONTROL);
-		if (ret)
-			goto err_minors;
-	}
-
 	if (drm_core_check_feature(dev, DRIVER_RENDER)) {
 		ret = drm_minor_alloc(dev, DRM_MINOR_RENDER);
 		if (ret)
@@ -663,6 +647,62 @@ void drm_dev_unref(struct drm_device *dev)
 }
 EXPORT_SYMBOL(drm_dev_unref);
 
+static int create_compat_control_link(struct drm_device *dev)
+{
+	struct drm_minor *minor;
+	char *name;
+	int ret;
+
+	if (!drm_core_check_feature(dev, DRIVER_MODESET))
+		return 0;
+
+	minor = *drm_minor_get_slot(dev, DRM_MINOR_PRIMARY);
+	if (!minor)
+		return 0;
+
+	/*
+	 * Some existing userspace out there uses the existing of the controlD*
+	 * sysfs files to figure out whether it's a modeset driver. It only does
+	 * readdir, hence a symlink is sufficient (and the least confusing
+	 * option). Otherwise controlD* is entirely unused.
+	 *
+	 * Old controlD chardev have been allocated in the range
+	 * 64-127.
+	 */
+	name = kasprintf(GFP_KERNEL, "controlD%d", minor->index + 64);
+	if (!name)
+		return -ENOMEM;
+
+	ret = sysfs_create_link(minor->kdev->kobj.parent,
+				&minor->kdev->kobj,
+				name);
+
+	kfree(name);
+
+	return ret;
+}
+
+static void remove_compat_control_link(struct drm_device *dev)
+{
+	struct drm_minor *minor;
+	char *name;
+
+	if (!drm_core_check_feature(dev, DRIVER_MODESET))
+		return;
+
+	minor = *drm_minor_get_slot(dev, DRM_MINOR_PRIMARY);
+	if (!minor)
+		return;
+
+	name = kasprintf(GFP_KERNEL, "controlD%d", minor->index);
+	if (!name)
+		return;
+
+	sysfs_remove_link(minor->kdev->kobj.parent, name);
+
+	kfree(name);
+}
+
 /**
  * drm_dev_register - Register DRM device
  * @dev: Device to register
@@ -701,6 +741,10 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags)
 	if (ret)
 		goto err_minors;
 
+	ret = create_compat_control_link(dev);
+	if (ret)
+		goto err_minors;
+
 	if (dev->driver->load) {
 		ret = dev->driver->load(dev, flags);
 		if (ret)
@@ -714,6 +758,7 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags)
 	goto out_unlock;
 
 err_minors:
+	remove_compat_control_link(dev);
 	drm_minor_unregister(dev, DRM_MINOR_PRIMARY);
 	drm_minor_unregister(dev, DRM_MINOR_RENDER);
 	drm_minor_unregister(dev, DRM_MINOR_CONTROL);
@@ -754,12 +799,33 @@ void drm_dev_unregister(struct drm_device *dev)
 	list_for_each_entry_safe(r_list, list_temp, &dev->maplist, head)
 		drm_legacy_rmmap(dev, r_list->map);
 
+	remove_compat_control_link(dev);
 	drm_minor_unregister(dev, DRM_MINOR_PRIMARY);
 	drm_minor_unregister(dev, DRM_MINOR_RENDER);
 	drm_minor_unregister(dev, DRM_MINOR_CONTROL);
 }
 EXPORT_SYMBOL(drm_dev_unregister);
 
+/**
+ * drm_dev_set_unique - Set the unique name of a DRM device
+ * @dev: device of which to set the unique name
+ * @name: unique name
+ *
+ * Sets the unique name of a DRM device using the specified string. Drivers
+ * can use this at driver probe time if the unique name of the devices they
+ * drive is static.
+ *
+ * Return: 0 on success or a negative error code on failure.
+ */
+int drm_dev_set_unique(struct drm_device *dev, const char *name)
+{
+	kfree(dev->unique);
+	dev->unique = kstrdup(name, GFP_KERNEL);
+
+	return dev->unique ? 0 : -ENOMEM;
+}
+EXPORT_SYMBOL(drm_dev_set_unique);
+
 /*
  * DRM Core
  * The DRM core module initializes all global DRM objects and makes them