[PATCH v5] drivers/base: return bus_add_driver() errors

[Yemingxuan <level_zero@qq.com>]

bus_add_driver() creates the driver's uevent attribute, adds the bus
driver groups and the bind/unbind files after the driver has already
been inserted into the bus and its module links have been made.  When
any of these fail it logs the failure and still returns 0.

The driver is then registered but incomplete: a driver without
bind/unbind cannot be bound or unbound from userspace, and a driver
without its uevent attribute can no longer emit uevent notifications.
driver_register() reports success, so neither the driver's init routine
nor its caller retries, and nothing else ever creates the missing
files.

The device side of the same driver model already treats the equivalent
steps this way: device_add() returns failures of the equivalent sysfs
operations to its caller, and device_del() undoes each one.
driver_register() already calls bus_remove_driver() when the group
registration after bus_add_driver() fails, and that branch is only
unreachable for failures inside bus_add_driver() because of the
unconditional successful return.

Propagate the errors so the existing unwind runs.  The new
out_remove_module label calls module_remove_driver() before falling
through to out_detach: bus_remove_driver() pairs every operation
bus_add_driver() performs in reverse order, but the symlinks
module_add_driver() creates live in the module's sysfs directory, not
under drv->p->kobj, so the kobject teardown does not remove them.
The attribute and the groups need no explicit removal because they live
under drv->p->kobj, and kobject_cleanup() drops the sysfs directory for
the caller.

The error messages are kept.  The return value of an initcall is not
printed by the initcall machinery, so dropping them would turn a
reported failure into a silent one.

These failures are not expected on a working system: driver_ktype
always supplies sysfs_ops, so -EINVAL is unreachable, no in-tree bus
defines a drv_group that collides with the built-in uevent, bind or
unbind attributes, and -ENOMEM needs memory pressure.  The point is not
a user-visible bug but keeping the driver model consistent with the
device side and leaving the failure reported.

Signed-off-by: Yemingxuan <level_zero@qq.com>
---
 Changes since v4:

 - Keep the error messages.  The return value of an initcall
   is not printed by the initcall machinery, so dropping them
   would turn a reported failure into a silent one.

 drivers/base/bus.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index d17bd91..a63e55c 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -775,25 +775,28 @@ int bus_add_driver(struct device_driver *drv)
 	if (error) {
 		printk(KERN_ERR "%s: uevent attr (%s) failed\n",
 			__func__, drv->name);
+		goto out_remove_module;
 	}
 	error = driver_add_groups(drv, sp->bus->drv_groups);
 	if (error) {
-		/* How the hell do we get out of this pickle? Give up */
 		printk(KERN_ERR "%s: driver_add_groups(%s) failed\n",
 			__func__, drv->name);
+		goto out_remove_module;
 	}
 
 	if (!drv->suppress_bind_attrs) {
 		error = add_bind_files(drv);
 		if (error) {
-			/* Ditto */
 			printk(KERN_ERR "%s: add_bind_files(%s) failed\n",
 				__func__, drv->name);
+			goto out_remove_module;
 		}
 	}
 
 	return 0;
 
+out_remove_module:
+	module_remove_driver(drv);
 out_detach:
 	driver_detach(drv);
 out_del_list:
-- 
2.34.1