Re: [Intel-gfx] [PATCH v2 12/14] drm/i915: Define multicast registers as a new type

[Jani Nikula <jani.nikula@linux.intel.com>]

On Fri, 30 Sep 2022, Matt Roper <matthew.d.roper@intel.com> wrote:
> diff --git a/drivers/gpu/drm/i915/i915_reg_defs.h b/drivers/gpu/drm/i915/i915_reg_defs.h
> index 8f486f77609f..e823869b9afd 100644
> --- a/drivers/gpu/drm/i915/i915_reg_defs.h
> +++ b/drivers/gpu/drm/i915/i915_reg_defs.h
> @@ -104,22 +104,16 @@ typedef struct {
>  
>  #define _MMIO(r) ((const i915_reg_t){ .reg = (r) })
>  
> -#define INVALID_MMIO_REG _MMIO(0)
> -
> -static __always_inline u32 i915_mmio_reg_offset(i915_reg_t reg)
> -{
> -	return reg.reg;
> -}
> +typedef struct {
> +	u32 reg;
> +} i915_mcr_reg_t;
>  
> -static inline bool i915_mmio_reg_equal(i915_reg_t a, i915_reg_t b)
> -{
> -	return i915_mmio_reg_offset(a) == i915_mmio_reg_offset(b);
> -}
> +#define INVALID_MMIO_REG _MMIO(0)
>  
> -static inline bool i915_mmio_reg_valid(i915_reg_t reg)
> -{
> -	return !i915_mmio_reg_equal(reg, INVALID_MMIO_REG);
> -}
> +/* These macros can be used on either i915_reg_t or i915_mcr_reg_t */
> +#define i915_mmio_reg_offset(r) (r.reg)
> +#define i915_mmio_reg_equal(a, b) (i915_mmio_reg_offset(a) == i915_mmio_reg_offset(b))
> +#define i915_mmio_reg_valid(r) (!i915_mmio_reg_equal(r, INVALID_MMIO_REG))
>  

I don't really like losing the type safety here. The whole and only
purpose of typedeffing i915_reg_t as a struct instead of just u32 was
the strict type safety.

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Graphics Center