linux-kernel - Re: [PATCH] Staging: emxx_udc: fix warning "sum of probable bitmasks, consider |"

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Date:   Thu, 6 Jun 2019 13:51:08 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Hariprasad Kelam <hariprasad.kelam@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Carmeli Tamir <carmeli.tamir@...il.com>,
        Nishad Kamdar <nishadkamdar@...il.com>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Staging: emxx_udc: fix warning "sum of probable
 bitmasks, consider |"

On Wed, Jun 05, 2019 at 12:04:43PM +0530, Hariprasad Kelam wrote:
> On Mon, Jun 03, 2019 at 09:04:57PM +0200, Greg Kroah-Hartman wrote:
> > On Tue, Jun 04, 2019 at 12:24:12AM +0530, Hariprasad Kelam wrote:
> > > Knowing the fact that operator '|' is faster than '+'.
> > > Its better we replace + with | in this case.
> > > 
> > > Issue reported by coccicheck
> > > drivers/staging/emxx_udc/emxx_udc.h:94:34-35: WARNING: sum of probable
> > > bitmasks, consider |
> > > 
> > > Signed-off-by: Hariprasad Kelam <hariprasad.kelam@...il.com>
> > > ---
> > >  drivers/staging/emxx_udc/emxx_udc.h | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/staging/emxx_udc/emxx_udc.h b/drivers/staging/emxx_udc/emxx_udc.h
> > > index b8c3dee..88d6bda 100644
> > > --- a/drivers/staging/emxx_udc/emxx_udc.h
> > > +++ b/drivers/staging/emxx_udc/emxx_udc.h
> > > @@ -91,7 +91,7 @@ int vbus_irq;
> > >  #define BIT30		0x40000000
> > >  #define BIT31		0x80000000
> > 
> > All of those BITXX defines should be removed and the "real" BIT(X) macro
> > used instead.
> Yes will send separate patch  to address this.
> > 
> > > -#define TEST_FORCE_ENABLE		(BIT18 + BIT16)
> > > +#define TEST_FORCE_ENABLE		(BIT18 | BIT16)
> > 
> > It really doesn't matter, a good compiler will have already turned this
> > into a constant value so you really do not know if this is less/faster
> > code or not, right?
> > 
> > Did you look at the output to verify this actually changed anything?
> > 
> > thanks,
> > 
> > greg k-h
> 
> Ok . Treating this as false postive from coccicheck.

I liked the patch.  | is way more normal and readable than +.  It's just
the commit message was bogus.

I would be very surprised if this coccicheck found anything that wasn't
a compile time constant like this.

regards,
dan carpenter