linux-kernel - Re: [PATCH v2 3/4] staging: iio: adt7316: fix the dac read calculation

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Date:   Sat, 5 Jan 2019 17:55:11 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Jeremy Fertic <jeremyfertic@...il.com>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Hartmut Knaack <knaack.h@....de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-iio@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org,
        Shreeya Patel <shreeya.patel23498@...il.com>
Subject: Re: [PATCH v2 3/4] staging: iio: adt7316: fix the dac read
 calculation

On Sat, 22 Dec 2018 21:57:42 -0700
Jeremy Fertic <jeremyfertic@...il.com> wrote:

> The calculation of the current dac value is using the wrong bits of the
> dac lsb register. Create two macros to shift the lsb register value into
> lsb position, depending on whether the dac is 10 or 12 bit. Initialize
> data to 0 so, with an 8 bit dac, the msb register value can be bitwise
> ORed with data.
> 
> Fixes: 35f6b6b86ede ("staging: iio: new ADT7316/7/8 and ADT7516/7/9 driver")
> Signed-off-by: Jeremy Fertic <jeremyfertic@...il.com>
Applied to the togreg branch of iio.git and pushed out as testing for
the autobuilders to play with it.

Thanks,

Jonathan

> ---
>  drivers/staging/iio/addac/adt7316.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/iio/addac/adt7316.c b/drivers/staging/iio/addac/adt7316.c
> index 80cc3420036b..d7f3d68e525b 100644
> --- a/drivers/staging/iio/addac/adt7316.c
> +++ b/drivers/staging/iio/addac/adt7316.c
> @@ -47,6 +47,8 @@
>  #define ADT7516_MSB_AIN3		0xA
>  #define ADT7516_MSB_AIN4		0xB
>  #define ADT7316_DA_DATA_BASE		0x10
> +#define ADT7316_DA_10_BIT_LSB_SHIFT	6
> +#define ADT7316_DA_12_BIT_LSB_SHIFT	4
>  #define ADT7316_DA_MSB_DATA_REGS	4
>  #define ADT7316_LSB_DAC_A		0x10
>  #define ADT7316_MSB_DAC_A		0x11
> @@ -1392,7 +1394,7 @@ static IIO_DEVICE_ATTR(ex_analog_temp_offset, 0644,
>  static ssize_t adt7316_show_DAC(struct adt7316_chip_info *chip,
>  				int channel, char *buf)
>  {
> -	u16 data;
> +	u16 data = 0;
>  	u8 msb, lsb, offset;
>  	int ret;
>  
> @@ -1417,7 +1419,11 @@ static ssize_t adt7316_show_DAC(struct adt7316_chip_info *chip,
>  	if (ret)
>  		return -EIO;
>  
> -	data = (msb << offset) + (lsb & ((1 << offset) - 1));
> +	if (chip->dac_bits == 12)
> +		data = lsb >> ADT7316_DA_12_BIT_LSB_SHIFT;
> +	else if (chip->dac_bits == 10)
> +		data = lsb >> ADT7316_DA_10_BIT_LSB_SHIFT;
> +	data |= msb << offset;
>  
>  	return sprintf(buf, "%d\n", data);
>  }