linux-kernel - Re: [PATCH v2 1/2] iio: adc: ti-ads8344: properly byte swap value

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Date:   Sat, 18 Apr 2020 16:06:08 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Gregory CLEMENT <gregory.clement@...tlin.com>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] iio: adc: ti-ads8344: properly byte swap value

On Thu, 16 Apr 2020 22:54:27 +0200
Alexandre Belloni <alexandre.belloni@...tlin.com> wrote:

> The first received byte is the MSB, followed by the LSB so the value needs
> to be byte swapped.
> 
> Also, the ADC actually has a delay of one clock on the SPI bus. Read three
> bytes to get the last bit.
> 
> Fixes: 8dd2d7c0fed7 ("iio: adc: Add driver for the TI ADS8344 A/DC chips")
> Signed-off-by: Alexandre Belloni <alexandre.belloni@...tlin.com>

Applied to the fixes-togreg branch of iio.git.  Marked for stable.

Random aside that I'll probably forget to clean up.

Driver includes iio/buffer.h and doesn't use it...

Thanks,

Jonathan


> ---
>  drivers/iio/adc/ti-ads8344.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/adc/ti-ads8344.c b/drivers/iio/adc/ti-ads8344.c
> index 9a460807d46d..abe4b56c847c 100644
> --- a/drivers/iio/adc/ti-ads8344.c
> +++ b/drivers/iio/adc/ti-ads8344.c
> @@ -29,7 +29,7 @@ struct ads8344 {
>  	struct mutex lock;
>  
>  	u8 tx_buf ____cacheline_aligned;
> -	u16 rx_buf;
> +	u8 rx_buf[3];
>  };
>  
>  #define ADS8344_VOLTAGE_CHANNEL(chan, si)				\
> @@ -89,11 +89,11 @@ static int ads8344_adc_conversion(struct ads8344 *adc, int channel,
>  
>  	udelay(9);
>  
> -	ret = spi_read(spi, &adc->rx_buf, 2);
> +	ret = spi_read(spi, adc->rx_buf, sizeof(adc->rx_buf));
>  	if (ret)
>  		return ret;
>  
> -	return adc->rx_buf;
> +	return adc->rx_buf[0] << 9 | adc->rx_buf[1] << 1 | adc->rx_buf[2] >> 7;
>  }
>  
>  static int ads8344_read_raw(struct iio_dev *iio,