Re: [PATCH v4 03/10] fixp-arith: add a linear interpolation function

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 10 Sep 2020 16:59:53 +0300
Dmitry Baryshkov <dmitry.baryshkov@linaro.org> wrote:

> From: Craig Tatlor <ctatlor97@gmail.com>
> 
> Adds a function to interpolate against two points,
> this is carried arount as a helper function by tons of drivers.
> 
> Signed-off-by: Craig Tatlor <ctatlor97@gmail.com>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

Seems sensible to have this.

Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  include/linux/fixp-arith.h | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/include/linux/fixp-arith.h b/include/linux/fixp-arith.h
> index 8396013785ef..281cb4f83dbe 100644
> --- a/include/linux/fixp-arith.h
> +++ b/include/linux/fixp-arith.h
> @@ -141,4 +141,23 @@ static inline s32 fixp_sin32_rad(u32 radians, u32 twopi)
>  #define fixp_cos32_rad(rad, twopi)	\
>  	fixp_sin32_rad(rad + twopi / 4, twopi)
>  
> +/**
> + * fixp_linear_interpolate() - interpolates a value from two known points
> + *
> + * @x0: x value of point 0
> + * @y0: y value of point 0
> + * @x1: x value of point 1
> + * @y1: y value of point 1
> + * @x: the linear interpolant
> + */
> +static inline int fixp_linear_interpolate(int x0, int y0, int x1, int y1, int x)
> +{
> +	if (y0 == y1 || x == x0)
> +		return y0;
> +	if (x1 == x0 || x == x1)
> +		return y1;
> +
> +	return y0 + ((y1 - y0) * (x - x0) / (x1 - x0));
> +}
> +
>  #endif