linux-kernel - Re: [PATCH v2 01/16] iio: adc: ad7768-1: Fix conversion result sign

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Message-ID: <20250201153630.03245bd9@jic23-huawei>
Date: Sat, 1 Feb 2025 15:36:30 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Jonathan Santos <Jonathan.Santos@...log.com>
Cc: <linux-iio@...r.kernel.org>, <devicetree@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, Sergiu Cuciurean
 <sergiu.cuciurean@...log.com>, <lars@...afoo.de>,
 <Michael.Hennerich@...log.com>, <marcelo.schmitt@...log.com>,
 <robh@...nel.org>, <krzk+dt@...nel.org>, <conor+dt@...nel.org>,
 <jonath4nns@...il.com>, <marcelo.schmitt1@...il.com>, David Lechner
 <dlechner@...libre.com>
Subject: Re: [PATCH v2 01/16] iio: adc: ad7768-1: Fix conversion result sign

On Mon, 27 Jan 2025 12:11:01 -0300
Jonathan Santos <Jonathan.Santos@...log.com> wrote:

> From: Sergiu Cuciurean <sergiu.cuciurean@...log.com>
> 
> The ad7768-1 ADC output code is two's complement, meaning that the voltage
> conversion result is a signed value.. Since the value is a 24 bit one,
> stored in a 32 bit variable, the sign should be extended in order to get
> the correct representation.
> 
> Also the channel description has been updated to signed representation,
> to match the ADC specifications.
> 
> Fixes: a5f8c7da3dbe ("iio: adc: Add AD7768-1 ADC basic support")
> Reviewed-by: David Lechner <dlechner@...libre.com>
> Reviewed-by: Marcelo Schmitt <marcelo.schmitt@...log.com>
> Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@...log.com>
Dropped.  Jonathan, this is missing your sign off.

> ---
> v2 Changes:
> * Patch moved to the start of the patch series.
> ---
>  drivers/iio/adc/ad7768-1.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/adc/ad7768-1.c b/drivers/iio/adc/ad7768-1.c
> index 113703fb7245..c3cf04311c40 100644
> --- a/drivers/iio/adc/ad7768-1.c
> +++ b/drivers/iio/adc/ad7768-1.c
> @@ -142,7 +142,7 @@ static const struct iio_chan_spec ad7768_channels[] = {
>  		.channel = 0,
>  		.scan_index = 0,
>  		.scan_type = {
> -			.sign = 'u',
> +			.sign = 's',
>  			.realbits = 24,
>  			.storagebits = 32,
>  			.shift = 8,
> @@ -371,7 +371,7 @@ static int ad7768_read_raw(struct iio_dev *indio_dev,
>  
>  		ret = ad7768_scan_direct(indio_dev);
>  		if (ret >= 0)
> -			*val = ret;
> +			*val = sign_extend32(ret, chan->scan_type.realbits - 1);
>  
>  		iio_device_release_direct_mode(indio_dev);
>  		if (ret < 0)