linux-kernel - Re: [PATCH v2] staging:iio:accel:adis16240: sign extend function avoiding code duplication

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Date:   Sat, 16 Jun 2018 19:02:26 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Karim Eshapa <karim.eshapa@...il.com>
Cc:     lars@...afoo.de, Michael.Hennerich@...log.com, knaack.h@....de,
        pmeerw@...erw.net, gregkh@...uxfoundation.org,
        linux-iio@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] staging:iio:accel:adis16240: sign extend function
 avoiding code duplication

On Tue, 12 Jun 2018 18:21:53 +0200
Karim Eshapa <karim.eshapa@...il.com> wrote:

> Use sign_extend32 kernel function instead of code duplication,
> Safe also for 16 bit. and remove declaration of bits variable not needed.
> 
> Signed-off-by: Karim Eshapa <karim.eshapa@...il.com>

Please consider how a patch is applied and resend as a v3 which can actually 
be applied.  Test it (by applying it yourself) to make sure you have everything correct...

Jonathan

> 
> >On Tue, 2018-06-12 at 01:38 +0200, Karim Eshapa wrote:  
> >> Use sign_extend32 kernel function instead of code duplication.
> >> Safe also for 16 bit.  
> >
> >Perhaps remove the bits declaration and assignments
> >and just use 9 directly.
> >  
> >> diff --git a/drivers/staging/iio/accel/adis16240.c b/drivers/staging/iio/accel/adis16240.c  
> >  
> >> @@ -292,9 +292,7 @@ static int adis16240_read_raw(struct iio_dev *indio_dev,
> >>               ret = adis_read_reg_16(st, addr, &val16);
> >>               if (ret)
> >>                       return ret;
> >> -             val16 &= (1 << bits) - 1;
> >> -             val16 = (s16)(val16 << (16 - bits)) >> (16 - bits);
> >> -             *val = val16;
> >> +             *val = sign_extend32(val16, bits - 1);
> >>               return IIO_VAL_INT;
> >>       case IIO_CHAN_INFO_PEAK:
> >>               bits = 10;
> >> @@ -302,9 +300,7 @@ static int adis16240_read_raw(struct iio_dev *indio_dev,
> >>               ret = adis_read_reg_16(st, addr, &val16);
> >>               if (ret)
> >>                       return ret;
> >> -             val16 &= (1 << bits) - 1;
> >> -             val16 = (s16)(val16 << (16 - bits)) >> (16 - bits);
> >> -             *val = val16;
> >> +             *val = sign_extend32(val16, bits - 1);
> >>               return IIO_VAL_INT;
> >>       }
> >>       return -EINVAL;  
> ---
>  drivers/staging/iio/accel/adis16240.c | 11 ++---------
>  1 file changed, 2 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/staging/iio/accel/adis16240.c b/drivers/staging/iio/accel/adis16240.c
> index fff6d99089cc..24e525f1ef25 100644
> --- a/drivers/staging/iio/accel/adis16240.c
> +++ b/drivers/staging/iio/accel/adis16240.c
> @@ -250,7 +250,6 @@ static int adis16240_read_raw(struct iio_dev *indio_dev,
>  {
>  	struct adis *st = iio_priv(indio_dev);
>  	int ret;
> -	int bits;
>  	u8 addr;
>  	s16 val16;
>  
> @@ -287,24 +286,18 @@ static int adis16240_read_raw(struct iio_dev *indio_dev,
>  		*val = 25000 / 244 - 0x133; /* 25 C = 0x133 */
>  		return IIO_VAL_INT;
>  	case IIO_CHAN_INFO_CALIBBIAS:
> -		bits = 10;
>  		addr = adis16240_addresses[chan->scan_index][0];
>  		ret = adis_read_reg_16(st, addr, &val16);
>  		if (ret)
>  			return ret;
> -		val16 &= (1 << bits) - 1;
> -		val16 = (s16)(val16 << (16 - bits)) >> (16 - bits);
> -		*val = val16;
> +		*val = sign_extend32(val16, 9);
>  		return IIO_VAL_INT;
>  	case IIO_CHAN_INFO_PEAK:
> -		bits = 10;
>  		addr = adis16240_addresses[chan->scan_index][1];
>  		ret = adis_read_reg_16(st, addr, &val16);
>  		if (ret)
>  			return ret;
> -		val16 &= (1 << bits) - 1;
> -		val16 = (s16)(val16 << (16 - bits)) >> (16 - bits);
> -		*val = val16;
> +		*val = sign_extend32(val16, 9);
>  		return IIO_VAL_INT;
>  	}
>  	return -EINVAL;