driver core: Export device_driver_attach()

This is intended as a replacement API for device_bind_driver(). It has at
least the following benefits:

- Internal locking. Few of the users of device_bind_driver() follow the
  locking rules

- Calls device driver probe() internally. Notably this means that devm
  support for probe works correctly as probe() error will call
  devres_release_all()

- struct device_driver -> dev_groups is supported

- Simplified calling convention, no need to manually call probe().

The general usage is for situations that already know what driver to bind
and need to ensure the bind is synchronized with other logic. Call
device_driver_attach() after device_add().

If probe() returns a failure then this will be preserved up through to the
error return of device_driver_attach().
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20210617142218.1877096-6-hch@lst.deSigned-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/base/base.h

@@ -152,7 +152,6 @@ extern int driver_add_groups(struct device_driver *drv,
 			     const struct attribute_group **groups);
 extern void driver_remove_groups(struct device_driver *drv,
 				 const struct attribute_group **groups);
-int device_driver_attach(struct device_driver *drv, struct device *dev);
 void device_driver_detach(struct device *dev);
 
 extern char *make_class_name(const char *name, struct kobject *kobj);

drivers/base/dd.c

@@ -471,6 +471,8 @@ static void driver_sysfs_remove(struct device *dev)
  * (It is ok to call with no other effort from a driver's probe() method.)
  *
  * This function must be called with the device lock held.
+ *
+ * Callers should prefer to use device_driver_attach() instead.
  */
 int device_bind_driver(struct device *dev)
 {
@@ -1065,6 +1067,7 @@ int device_driver_attach(struct device_driver *drv, struct device *dev)
 		return -EAGAIN;
 	return ret;
 }
+EXPORT_SYMBOL_GPL(device_driver_attach);
 
 static void __driver_attach_async_helper(void *_dev, async_cookie_t cookie)
 {

include/linux/device.h

@@ -845,6 +845,8 @@ static inline void *dev_get_platdata(const struct device *dev)
  * Manual binding of a device to driver. See drivers/base/bus.c
  * for information on use.
  */
+int __must_check device_driver_attach(struct device_driver *drv,
+				      struct device *dev);
 int __must_check device_bind_driver(struct device *dev);
 void device_release_driver(struct device *dev);
 int  __must_check device_attach(struct device *dev);