Re: [PATCH 01/11] iio: Add some helper macros for unit conversion

[Jonathan Cameron <jic23@kernel.org>]

On 10/15/2012 10:35 AM, Lars-Peter Clausen wrote:
> Some datasheets use a different unit to specify the channel scale than what IIO
> expects it to be. This patch adds two helper macros which allow to convert units
> commonly used in datasheets to IIO units:
>
>  * acceleration: g -> meter / second**2
>  * angular velocity: degree (/ second) -> rad (/ second)
>
> This makes it much more convenient to specify and also easier to verify a
> channel's scale attribute.
>
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Good idea applied to togreg branch of iio.git (or at least will
be when I get home from travelling).

> ---
>  include/linux/iio/iio.h |   16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
>
> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> index c0ae76a..7806c24 100644
> --- a/include/linux/iio/iio.h
> +++ b/include/linux/iio/iio.h
> @@ -618,4 +618,20 @@ static inline struct dentry *iio_get_debugfs_dentry(struct iio_dev *indio_dev)
>  };
>  #endif
>
> +/**
> + * IIO_DEGREE_TO_RAD() - Convert degree to rad
> + * @deg: A value in degree
> + *
> + * Returns the given value converted from degree to rad
> + */
> +#define IIO_DEGREE_TO_RAD(deg) (((deg) * 314159ULL + 9000000ULL) / 18000000ULL)
> +
> +/**
> + * IIO_G_TO_M_S_2() - Convert g to meter / second**2
> + * @g: A value in g
> + *
> + * Returns the given value converted from g to meter / second**2
> + */
> +#define IIO_G_TO_M_S_2(g) ((g) * 980665ULL / 100000ULL)
> +
>  #endif /* _INDUSTRIAL_IO_H_ */
>