[PATCH] device_for_each_child(): kill pointless warning noise

[PATCH] device_for_each_child(): kill pointless warning noise

[Jeff Garzik]

As the last patch demonstrated, it is quite valid for a caller to ignore
the return value of device_for_each_child(), given that the return value
is wholly dependent on the actor -- which in practice often has a
hardcoded return value.

Please apply, to reduce a portion of the warning explosion seen in
current linux-2.6.git.

Signed-off-by: Jeff Garzik <jeff@garzik.org>

diff --git a/include/linux/device.h b/include/linux/device.h
index 662e6a1..9d4f6a9 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -393,7 +393,7 @@ extern void device_unregister(struct dev
 extern void device_initialize(struct device * dev);
 extern int __must_check device_add(struct device * dev);
 extern void device_del(struct device * dev);
-extern int __must_check device_for_each_child(struct device *, void *,
+extern int device_for_each_child(struct device *, void *,
 		     int (*fn)(struct device *, void *));
 extern int device_rename(struct device *dev, char *new_name);
 

Re: [PATCH] device_for_each_child(): kill pointless warning noise

[Andrew Morton]

On Wed, 27 Sep 2006 21:05:18 -0400
Jeff Garzik <jeff@garzik.org> wrote:

> As the last patch demonstrated, it is quite valid for a caller to ignore
> the return value of device_for_each_child(), given that the return value
> is wholly dependent on the actor -- which in practice often has a
> hardcoded return value.

Yes, but almost all of the instances which you found are flat-out *wrong*. 
They're returning 0 or 1 at random places in the callchain because they're
calling intermediate void-returning functions which are themselves dropping
error codes on the floor instead of returning them.

Let no error go unhandled!

Re: [PATCH] device_for_each_child(): kill pointless warning noise

[Jeff Garzik]

Andrew Morton wrote:
> On Wed, 27 Sep 2006 21:05:18 -0400
> Jeff Garzik <jeff@garzik.org> wrote:
> 
>> As the last patch demonstrated, it is quite valid for a caller to ignore
>> the return value of device_for_each_child(), given that the return value
>> is wholly dependent on the actor -- which in practice often has a
>> hardcoded return value.
> 
> Yes, but almost all of the instances which you found are flat-out *wrong*. 
> They're returning 0 or 1 at random places in the callchain because they're
> calling intermediate void-returning functions which are themselves dropping
> error codes on the floor instead of returning them.

"almost all"  Thus it is wrong to _force_ the usage model on the caller.

It should be obvious that a simple search need not _require_ a dummy 
return value, that is promptly ignored.

See previous email for examples.

	Jeff

Re: [PATCH] device_for_each_child(): kill pointless warning noise

[Alan Cox]

Ar Mer, 2006-09-27 am 21:50 -0400, ysgrifennodd Jeff Garzik:
> "almost all"  Thus it is wrong to _force_ the usage model on the caller.
> 
> It should be obvious that a simple search need not _require_ a dummy 
> return value, that is promptly ignored.

How about just adding an explicit device_for_each_child_noret() or
similar function so that the safety check stays as well for the usual
case.

Alan