[PATCH v2] drm: Introduce drm_set_unique()

[Thierry Reding]

From: Thierry Reding <treding at nvidia.com>

Add a helper function that allows drivers to statically set the unique
name of the device. This will allow platform and USB drivers to get rid
of their DRM bus implementations and directly use drm_dev_alloc() and
drm_dev_register().

Signed-off-by: Thierry Reding <treding at nvidia.com>
---
Changes in v2:
- move drm_set_unique() to drivers/gpu/drm/drm_stub.c
- add kernel-doc

 drivers/gpu/drm/drm_ioctl.c | 23 +++++++++++++++++------
 drivers/gpu/drm/drm_stub.c  | 24 ++++++++++++++++++++++++
 include/drm/drmP.h          |  3 +++
 3 files changed, 44 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index 2dd3a6d8382b..1b082aeb4098 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -131,13 +131,24 @@ static int drm_set_busid(struct drm_device *dev, struct drm_file *file_priv)
 	if (master->unique != NULL)
 		drm_unset_busid(dev, master);
 
-	ret = dev->driver->bus->set_busid(dev, master);
-	if (ret)
-		goto err;
+	if (dev->driver->bus && dev->driver->bus->set_busid) {
+		ret = dev->driver->bus->set_busid(dev, master);
+		if (ret) {
+			drm_unset_busid(dev, master);
+			return ret;
+		}
+	} else {
+		WARN(dev->unique == NULL,
+		     "No drm_bus.set_busid() implementation provided by %ps. "
+		     "Set the unique name explicitly using drm_set_unique().",
+		     dev->driver);
+
+		master->unique = kstrdup(dev->unique, GFP_KERNEL);
+		if (master->unique)
+			master->unique_len = strlen(dev->unique);
+	}
+
 	return 0;
-err:
-	drm_unset_busid(dev, master);
-	return ret;
 }
 
 /**
diff --git a/drivers/gpu/drm/drm_stub.c b/drivers/gpu/drm/drm_stub.c
index 3a8e832ad151..d0c7c78aa7f4 100644
--- a/drivers/gpu/drm/drm_stub.c
+++ b/drivers/gpu/drm/drm_stub.c
@@ -532,6 +532,29 @@ static void drm_fs_inode_free(struct inode *inode)
 }
 
 /**
+ * drm_set_unique - Set the unique name of a DRM device
+ * @dev: device of which to set the unique name
+ * @fmt: format string for unique name
+ *
+ * Sets the unique name of a DRM device using the specified format string and
+ * a variable list of arguments. Drivers can use this at driver probe time if
+ * the unique name of the devices they drive is static.
+ */
+int drm_set_unique(struct drm_device *dev, const char *fmt, ...)
+{
+	va_list ap;
+
+	kfree(dev->unique);
+
+	va_start(ap, fmt);
+	dev->unique = kvasprintf(GFP_KERNEL, fmt, ap);
+	va_end(ap);
+
+	return dev->unique ? 0 : -ENOMEM;
+}
+EXPORT_SYMBOL(drm_set_unique);
+
+/**
  * drm_dev_alloc - Allocate new drm device
  * @driver: DRM driver to allocate device for
  * @parent: Parent device object
@@ -646,6 +669,7 @@ static void drm_dev_release(struct kref *ref)
 	drm_minor_free(dev, DRM_MINOR_CONTROL);
 
 	mutex_destroy(&dev->master_mutex);
+	kfree(dev->unique);
 	kfree(dev);
 }
 
diff --git a/include/drm/drmP.h b/include/drm/drmP.h
index 8c80c1894b41..d6da03c1ca3c 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1158,6 +1158,8 @@ struct drm_device {
 	struct drm_vma_offset_manager *vma_offset_manager;
 	/*@} */
 	int switch_power_state;
+
+	char *unique;
 };
 
 #define DRM_SWITCH_POWER_ON 0
@@ -1608,6 +1610,7 @@ static __inline__ void drm_core_dropmap(struct drm_local_map *map)
 
 #include <drm/drm_mem_util.h>
 
+int drm_set_unique(struct drm_device *dev, const char *fmt, ...);
 struct drm_device *drm_dev_alloc(struct drm_driver *driver,
 				 struct device *parent);
 void drm_dev_ref(struct drm_device *dev);
-- 
1.9.2