On 12/12/2013 06:24 AM, Laxman Dewangan wrote:
> Add of_property_read_s32() to read the signed 32bit number
> from dt property value. This supports to pass the -ve numbers
> from dt. Use 2's complement method for represnting negative number
> and passed as u32 from dts. When reading back the value, again
> converted to 2's complement if msb shows as 1.
> diff --git a/include/linux/of.h b/include/linux/of.h
> +static inline int of_property_read_s32(const struct device_node *np,
> + const char *propname,
> + s32 *out_value)
> +{
> + u32 val;
> + int ret;
> +
> + ret = of_property_read_u32(np, propname, &val);
> + if (ret < 0)
> + return ret;
> +
> + /* 2's complement if MSB is 1 */
> + *out_value = (val & 0x80000000U) ? -((val ^ 0xFFFFFFFFU) + 1) : val;
I may not be thinking straight today since I have a cold, but doesn't
patch 2/2 encode negative values as 2's complement, and an s32 variable
in the kernel is also encoded as 2's complement, so all you need here is
a cast:
*out_value = (s32)val;
... since the cast doesn't change the binary representation?
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