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SubjectRe: [PATCH] staging/comedi/dt282x: avoid integer overflow warning
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On Tuesday 15 March 2016 21:35:40 Hartley Sweeten wrote:
> On Monday, March 14, 2016 3:48 PM, Arnd Bergmann wrote:
> > gcc-6 warns about passing negative signed integer into swab16()
> > in the dt282x driver:
>
> <snip>
>
> > The warning makes sense, though the code is correct as far as I
> > can tell.
> >
> > This disambiguates the operation by making the constant expressions
> > we pass here explicitly 'unsigned', which helps to avoid the warning.
> >
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> > ---
> > drivers/staging/comedi/drivers/dt282x.c | 62 ++++++++++++++++-----------------
> > 1 file changed, 31 insertions(+), 31 deletions(-)
> >
> > diff --git a/drivers/staging/comedi/drivers/dt282x.c b/drivers/staging/comedi/drivers/dt282x.c
> > index 40bf00984fa5..d4d45c759c62 100644
> > --- a/drivers/staging/comedi/drivers/dt282x.c
> > +++ b/drivers/staging/comedi/drivers/dt282x.c
> > @@ -69,48 +69,48 @@
> > * Register map
> > */
> > #define DT2821_ADCSR_REG 0x00
> > -#define DT2821_ADCSR_ADERR (1 << 15)
> > -#define DT2821_ADCSR_ADCLK (1 << 9)
> > -#define DT2821_ADCSR_MUXBUSY (1 << 8)
> > -#define DT2821_ADCSR_ADDONE (1 << 7)
> > -#define DT2821_ADCSR_IADDONE (1 << 6)
> > +#define DT2821_ADCSR_ADERR (1u << 15)
>
> Changing all of these to use the BIT() macro should also avoid the warning.

Yes, but it won't work for the ones that have more than one bit:

#define DT2821_SUPCSR_DS_AD_TRIG (3 << 10)

I considered using BIT() but decided against it for consistency.

Arnd

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