[Intel-gfx] [PATCH v3 1/3] drm/i915: introduce REG_BIT() and REG_GENMASK() to define register contents

[Michal Wajdeczko]

On Wed, 27 Feb 2019 18:02:36 +0100, Jani Nikula <jani.nikula at intel.com>  
wrote:

> @@ -116,6 +116,34 @@
>   *  #define GEN8_BAR                    _MMIO(0xb888)
>   */
> +/**
> + * REG_BIT() - Prepare a u32 bit value
> + * @__n: 0-based bit number
> + *
> + * Local wrapper for BIT() to force u32, with compile time checks.
> + *
> + * @return: Value with bit @__n set.
> + */
> +#define REG_BIT(__n)							\
> +	((u32)(BIT(__n) +						\
> +	       BUILD_BUG_ON_ZERO(__builtin_constant_p(__n) &&		\
> +				 ((__n) < 0 || (__n) > 31))))

Maybe to simplify the code we can define this macro using macro below:

#define REG_BIT(__n) REG_GENMASK(__n, __n)

> +
> +/**
> + * REG_GENMASK() - Prepare a continuous u32 bitmask
> + * @__high: 0-based high bit
> + * @__low: 0-based low bit
> + *
> + * Local wrapper for GENMASK() to force u32, with compile time checks.
> + *
> + * @return: Continuous bitmask from @__high to @__low, inclusive.
> + */
> +#define REG_GENMASK(__high, __low)					\
> +	((u32)(GENMASK(__high, __low) +					\
> +	       BUILD_BUG_ON_ZERO(__builtin_constant_p(__high) &&	\
> +				 __builtin_constant_p(__low) &&		\
> +				 ((__low) < 0 || (__high) > 31 || (__low) > (__high)))))
> +

nit: Since we are defining new set of macros, do we really have to follow
naming of the underlying macros? maybe we can can have clear new names:

	REG_BIT(n)
	REG_BITS(hi,low)

Thanks,
Michal