linux-kernel - Re: [PATCH] checkpatch: Check for illegal return codes

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Date:   Tue, 03 Jul 2018 12:37:24 -0700
From:   Joe Perches <joe@...ches.com>
To:     pheragu@...eaurora.org
Cc:     apw@...onical.com, linux-kernel@...r.kernel.org,
        ckadabi@...eaurora.org, tsoni@...eaurora.org,
        bryanh@...eaurora.org, Patrick Pannuto <ppannuto@...eaurora.org>,
        Stepan Moskovchenko <stepanm@...eaurora.org>
Subject: Re: [PATCH] checkpatch: Check for illegal return codes

On Tue, 2018-07-03 at 12:07 -0700, pheragu@...eaurora.org wrote:
> On 2018-07-03 11:19, Joe Perches wrote:
> > On Tue, 2018-07-03 at 11:09 -0700, Prakruthi Deepak Heragu wrote:
> > > The only legal integer return is 0, anything else
> > > following "return" should be -ERRCODE or a function.
> > > 
> > > http://lkml.org/lkml/2010/7/23/318
> > >   There's lots of "return -1;" statements in this patch - it's obscene
> > >   that this is used to indicate "some error occurred" in kernel space
> > >   rather than a real errno value - even when an existing function
> > >   (eg, request_irq) gave you an error code already.
[]
> > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> > @@ -6197,6 +6197,12 @@ sub process {
> > >  			     "switch default: should use break\n" . $herectx);
> > >  		}
> > > 
> > > +# check for return codes on error paths
> > > +		if ($line =~ /\breturn\s+-\d+/) {
> > > +			ERROR("NO_ERROR_CODE",
> > > +			      "illegal return value, please use an error code");
> > > +		}
> > > +
> > 
> > Substitute illegal to invalid as this wouldn't be illegal.
> > It might be invalid and this needs a newline and $herecurr
> > 
> > I'm not sure this is even useful.
> > 
> > There are _way_ too many of these already existing
> > and simple return identifiers can be OK.
> > 
> > $ git grep -P '\breturn\s*\-(?!0)\d+' | wc -l
> > 10193
> > 
> > and
> > 
> > $ git grep -P '\breturn\s*\-(?!1)\d+' | wc -l
> > 240
> 
> True. However, this would be helpful to avoid usage of such return 
> statements in the future.

Maybe use CHK and not ERROR and maybe the output message
could be something like "Prefer 'return -<APPROPRIATE_ERRNO>'"