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

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Date:   Mon, 11 Jun 2018 16:57:24 -0700
From:   Joe Perches <joe@...ches.com>
To:     Karim Eshapa <karim.eshapa@...il.com>, lars@...afoo.de
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:adis16240: sign extend function
 avoiding code duplication

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;