linux-kernel - Re: [PATCH 7/8] drivers/i2c/busses/i2c-amd8111.c: Fix unsigned return type

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Date:	Wed, 8 Sep 2010 11:48:17 +0200 (CEST)
From:	Julia Lawall <julia@...u.dk>
To:	Jean Delvare <khali@...ux-fr.org>
Cc:	"Ben Dooks (em, bedded platforms)" <ben-linux@...ff.org>,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 7/8] drivers/i2c/busses/i2c-amd8111.c: Fix unsigned return
  type

OK, thanks. I will look at the code again.

julia


On Wed, 8 Sep 2010, Jean Delvare wrote:

> Hi Julia,
> 
> On Wed, 8 Sep 2010 07:58:45 +0200 (CEST), Julia Lawall wrote:
> > From: Julia Lawall <julia@...u.dk>
> > 
> > In each case, the function has an unsigned return type, but returns a
> > negative constant to indicate an error condition.  The result of calling
> > the function is always stored in a variable of type (signed) int, and thus
> > unsigned can be dropped from the return type.
> > 
> > A sematic match that finds this problem is as follows:
> > (http://coccinelle.lip6.fr/)
> > 
> > // <smpl>
> > @exists@
> > identifier f;
> > constant C;
> > @@
> > 
> >  unsigned f(...)
> >  { <+...
> > *  return -C;
> >  ...+> }
> > // </smpl>
> > 
> > Signed-off-by: Julia Lawall <julia@...u.dk>
> > 
> > ---
> >  drivers/i2c/busses/i2c-amd8111.c |    4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/i2c/busses/i2c-amd8111.c b/drivers/i2c/busses/i2c-amd8111.c
> > index af1e5e2..02a3726 100644
> > --- a/drivers/i2c/busses/i2c-amd8111.c
> > +++ b/drivers/i2c/busses/i2c-amd8111.c
> > @@ -69,7 +69,7 @@ static struct pci_driver amd8111_driver;
> >   * ACPI 2.0 chapter 13 access of registers of the EC
> >   */
> >  
> > -static unsigned int amd_ec_wait_write(struct amd_smbus *smbus)
> > +static int amd_ec_wait_write(struct amd_smbus *smbus)
> >  {
> >  	int timeout = 500;
> >  
> > @@ -85,7 +85,7 @@ static unsigned int amd_ec_wait_write(struct amd_smbus *smbus)
> >  	return 0;
> >  }
> >  
> > -static unsigned int amd_ec_wait_read(struct amd_smbus *smbus)
> > +static int amd_ec_wait_read(struct amd_smbus *smbus)
> >  {
> >  	int timeout = 500;
> >  
> > 
> 
> Thanks for reporting. Unfortunately the fix above is incomplete.
> amd_ec_wait_write() and amd_ec_wait_read() are called by amd_ec_read()
> and amd_ec_write(), which will now attempt to return negative error
> codes as unsigned ints. So amd_ec_read() and amd_ec_write() must have
> their return type fixed too.
> 
> Note that the driver code never checks for errors returned by
> amd_ec_read() or amd_ec_write() anyway, so the fix alone is a no-op. A
> real fix would have to also update the caller sites to properly deal
> with errors if then happen.
> 
> -- 
> Jean Delvare
> --
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