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Commit a5462516 authored by Timur Tabi's avatar Timur Tabi Committed by Greg Kroah-Hartman
Browse files

driver-core: document restrictions on device_rename() 



Add text, courtesy of Kay Sievers, that provides some background on
device_rename() and why it shouldn't be used.

Signed-off-by: default avatarTimur Tabi <timur@freescale.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent ebf53826

drivers/base/core.c

+28 −1
Original line number Diff line number Diff line
@@ -1551,7 +1551,34 @@ EXPORT_SYMBOL_GPL(device_destroy); 
 * on the same device to ensure that new_name is valid and

 * won't conflict with other devices.

 *

 * "Never use this function, bad things will happen" - gregkh

 * Note: Don't call this function.  Currently, the networking layer calls this

 * function, but that will change.  The following text from Kay Sievers offers

 * some insight:

 *

 * Renaming devices is racy at many levels, symlinks and other stuff are not

 * replaced atomically, and you get a "move" uevent, but it's not easy to

 * connect the event to the old and new device. Device nodes are not renamed at

 * all, there isn't even support for that in the kernel now.

 *

 * In the meantime, during renaming, your target name might be taken by another

 * driver, creating conflicts. Or the old name is taken directly after you

 * renamed it -- then you get events for the same DEVPATH, before you even see

 * the "move" event. It's just a mess, and nothing new should ever rely on

 * kernel device renaming. Besides that, it's not even implemented now for

 * other things than (driver-core wise very simple) network devices.

 *

 * We are currently about to change network renaming in udev to completely

 * disallow renaming of devices in the same namespace as the kernel uses,

 * because we can't solve the problems properly, that arise with swapping names

 * of multiple interfaces without races. Means, renaming of eth[0-9]* will only

 * be allowed to some other name than eth[0-9]*, for the aforementioned

 * reasons.

 *

 * Make up a "real" name in the driver before you register anything, or add

 * some other attributes for userspace to find the device, or use udev to add

 * symlinks -- but never rename kernel devices later, it's a complete mess. We

 * don't even want to get into that and try to implement the missing pieces in

 * the core. We really have other pieces to fix in the driver core mess. :)

 */

int device_rename(struct device *dev, const char *new_name)

{