Messages in this thread | | | Date | Tue, 11 Jul 2006 14:51:17 -0700 | From | Andrew Morton <> | Subject | Re: [mm Patch] isdn4linux: Gigaset driver: fix __must_check warning |
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Tilman Schmidt <tilman@imap.cc> wrote: > > This patch to the Siemens Gigaset driver fixes the compile warning > "ignoring return value of 'class_device_create_file', declared with > attribute warn_unused_result" appearing with CONFIG_ENABLE_MUST_CHECK=y > in release 2.6.18-rc1-mm1. > > Signed-off-by: Tilman Schmidt <tilman@imap.cc> > Acked-by: Hansjoerg Lipp <hjlipp@web.de> > --- > > proc.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletion(-) > > --- linux-2.6.18-rc1-orig/drivers/isdn/gigaset/proc.c 2006-07-09 17:19:49.000000000 +0200 > +++ linux-2.6.18-rc1-mm1-work/drivers/isdn/gigaset/proc.c 2006-07-09 18:31:15.000000000 +0200 > @@ -83,5 +83,6 @@ void gigaset_init_dev_sysfs(struct cards > return; > > gig_dbg(DEBUG_INIT, "setting up sysfs"); > - class_device_create_file(cs->class, &class_device_attr_cidmode); > + if (class_device_create_file(cs->class, &class_device_attr_cidmode)) > + dev_warn(cs->dev, "could not create sysfs attribute\n"); > }
hm.
With this change we'll emit a warning (actually it's an error - I'll make it dev_err(), OK?) and then we'll continue execution, pretending that the sysfs file actually got registered. Later, we'll try to unregister a not-registered sysfs file.
So it's all a bit flakey when you look at it in a dumb fashion.
But I think the patch is OK - if that class_device_create_file() fails, then there's some other bug somewhere, and the warning you've added is sufficient - it tells the developers what the initial failure was, when it happens. So later, if someone reports a crash, we'll see that warning in their logs and it'll lead us to the real bug. We certainly couldn't justify adding additional code which attempts to "continue working" if the class_device_create_file() fails, because it just shouldn't fail.
It's probable that the message will never come out ever, so it's not worth adding a ton of code to support this.
It'd be better if we had a class_device_create_file_warn() which does the warning for you: its semantics are "this is expected to succeed". But if we do that to class_device_create_file() then we'd need to do it to 200 other things too.
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