linux-kernel - Re: [PATCH v2 1/5] iio: accel: bma400: Fix the scale min and max macro values

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Message-ID: <20220327173120.78fd5148@jic23-huawei>
Date:   Sun, 27 Mar 2022 17:31:20 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Jagath Jog J <jagathjog1996@...il.com>
Cc:     dan@...obertson.com, andy.shevchenko@...il.com,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/5] iio: accel: bma400: Fix the scale min and max
 macro values

On Sun, 27 Mar 2022 01:11:42 +0530
Jagath Jog J <jagathjog1996@...il.com> wrote:

> Changing the scale macro values to match the bma400 sensitivity
> for 1 LSB of all the available ranges.
> 
> Signed-off-by: Jagath Jog J <jagathjog1996@...il.com>
Hi Jagath,

> ---
>  drivers/iio/accel/bma400.h | 22 ++++++++++++++++++++--
>  1 file changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/accel/bma400.h b/drivers/iio/accel/bma400.h
> index c4c8d74155c2..190366debdb3 100644
> --- a/drivers/iio/accel/bma400.h
> +++ b/drivers/iio/accel/bma400.h
> @@ -83,8 +83,26 @@
>  #define BMA400_ACC_ODR_MIN_WHOLE_HZ 25
>  #define BMA400_ACC_ODR_MIN_HZ       12
>  
> -#define BMA400_SCALE_MIN            38357
> -#define BMA400_SCALE_MAX            306864
> +/* BMA400_SCALE_MIN macro value represents m/s^2 for 1 LSB before
Multiline comment syntax in IIO is
/*
 * BMA400....

> + * converting to micro values for +-2g range.
> + *
> + * For +-2g - 1 LSB = 0.976562 milli g = 0.009576 m/s^2
> + * For +-4g - 1 LSB = 1.953125 milli g = 0.019153 m/s^2
> + * For +-16g - 1 LSB = 7.8125 milli g = 0.076614 m/s^2
> + *
> + * The raw value which is used to select the different ranges is determined
> + * by the first bit set position from the scale value, so BMA400_SCALE_MIN
> + * should be odd.
> + *
> + * Scale values for +-2g, +-4g, +-8g and +-16g is populated into bma400_scales
> + * array by left shifting BMA400_SCALE_MIN.
> + * eg:
> + * To select +-2g = 9577 << 0 = raw value to write is 0.
> + * To select +-8g = 9577 << 2 = raw value to write is 2.
> + * To select +-16g = 9677 << 3 = raw value to write is 3.

9667?

> + */
> +#define BMA400_SCALE_MIN            9577
> +#define BMA400_SCALE_MAX            76617
>  
>  #define BMA400_NUM_REGULATORS       2
>  #define BMA400_VDD_REGULATOR        0