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

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Date:   Sun, 10 Jun 2018 15:34:44 -0700
From:   Joe Perches <joe@...ches.com>
To:     Karim Eshapa <karim.eshapa@...il.com>, lars@...afoo.de,
        Himanshu Jha <himanshujha199640@...il.com>
Cc:     Michael.Hennerich@...log.com, jic23@...nel.org, 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] staging:iio:accel: use sign extend function avoiding
 code duplication

On Mon, 2018-06-11 at 00:09 +0200, Karim Eshapa wrote:
> Use sign_extend32 kernel function instead of code duplication.
> This function is also safe for 16 bits.

Firstly:

This file is not in staging anymore.
Please use the -next tree for patches.

> diff --git a/drivers/staging/iio/accel/adis16201.c b/drivers/staging/iio/accel/adis16201.c
[]
> @@ -227,9 +227,7 @@ static int adis16201_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);
>  		return IIO_VAL_INT;
>  	}

Secondly:

A similar patch with a different bits value was
already applied.

Please verify the appropriate bits value.

commit e7f3bfb7eb7d9307c0c157f82fceb228f0aec1d9
Author: Himanshu Jha <himanshujha199640@...il.com>
Date:   Sat Mar 17 01:36:23 2018 +0530

    Staging: iio: accel: adis16201: Use sign_extend32 function
    
    Use sign_extned32() for 32 bit sign extending rather than hard coding.
    
    Signed-off-by: Himanshu Jha <himanshujha199640@...il.com>
    Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
---
 drivers/staging/iio/accel/adis16201.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/iio/accel/adis16201.c b/drivers/staging/iio/accel/adis16201.c
index 87ad3d421c12..526dde481f84 100644
--- a/drivers/staging/iio/accel/adis16201.c
+++ b/drivers/staging/iio/accel/adis16201.c
@@ -173,9 +173,8 @@ static int adis16201_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;
        }