Re: [RFC 1/4] drm/i915: Add Display Gen info.

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

On Tue, 30 Oct 2018, Lucas De Marchi <lucas.de.marchi@gmail.com> wrote:
> On Tue, Oct 30, 2018 at 11:52:30AM +0200, Jani Nikula wrote:
>> On Mon, 29 Oct 2018, Rodrigo Vivi <rodrigo.vivi@intel.com> wrote:
>> > +#define IS_DISPLAY_GEN2(dev_priv)	(!!((dev_priv)->info.display_gen_mask \
>> > +					    & BIT(2)))
>> > +#define IS_DISPLAY_GEN3(dev_priv)	(!!((dev_priv)->info.display_gen_mask \
>> > +					    & BIT(3)))
>> > +#define IS_DISPLAY_GEN4(dev_priv)	(!!((dev_priv)->info.display_gen_mask \
>> > +					    & BIT(4)))
>> > +#define IS_DISPLAY_GEN5(dev_priv)	(!!((dev_priv)->info.display_gen_mask \
>> > +					    & BIT(5)))
>> > +#define IS_DISPLAY_GEN6(dev_priv)	(!!((dev_priv)->info.display_gen_mask \
>> > +					    & BIT(6)))
>> > +#define IS_DISPLAY_GEN7(dev_priv)	(!!((dev_priv)->info.display_gen_mask \
>> > +					    & BIT(7)))
>> > +#define IS_DISPLAY_GEN8(dev_priv)	(!!((dev_priv)->info.display_gen_mask \
>> > +					    & BIT(8)))
>> > +#define IS_DISPLAY_GEN9(dev_priv)	(!!((dev_priv)->info.display_gen_mask \
>> > +					    & BIT(9)))
>> > +#define IS_DISPLAY_GEN10(dev_priv)	(!!((dev_priv)->info.display_gen_mask \
>> > +					    & BIT(10)))
>> > +#define IS_DISPLAY_GEN11(dev_priv)	(!!((dev_priv)->info.display_gen_mask \
>> > +					    & BIT(11)))
>> 
>> I know this is the same pattern as in IS_GEN<N> above, but shouldn't the
>> compiler end up with the same result if these were simply:
>> 
>> #define IS_DISPLAY_GEN2(dev_priv) IS_DISPLAY_GEN(dev_priv, 2, 2)
>
>
> humn... maybe this is too magic, but it works for me and I didn't add any additional
> macro to the kernel to implement it :)
>
> [CI, DON'T TEST THIS] diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> [CI, DON'T TEST THIS] index 554627dc623c..02a8b51fd733 100644
> [CI, DON'T TEST THIS] --- a/drivers/gpu/drm/i915/i915_drv.h
> [CI, DON'T TEST THIS] +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2385,9 +2385,15 @@ intel_info(const struct drm_i915_private *dev_priv)
>  	GENMASK((e) - 1, (s) - 1))
>  
>  /* Returns true if Gen is in inclusive range [Start, End] */
> -#define IS_GEN(dev_priv, s, e) \
> +#define _IS_GEN_ARG2(dev_priv, s, e) \
>  	(!!((dev_priv)->info.gen_mask & INTEL_GEN_MASK((s), (e))))
>  
> +#define _IS_GEN_ARG1(dev_priv, g) \
> +	(!!((dev_priv)->info.gen_mask & BIT((g) - 1)))
> +
> +#define IS_GEN(dev_priv, ...) \
> +	CONCATENATE(_IS_GEN_ARG, COUNT_ARGS(__VA_ARGS__))((dev_priv), ##__VA_ARGS__)
> +
>  /*
>   * Return true if revision is in range [since,until] inclusive.
>   *
>
>
> So we could use IS_GEN(dev_priv, 2) as well as IS_GEN(dev_priv, 2, 4), which IMO is very clear.
> The same would apply for IS_DISPLAY_GEN() version. And if they generate the same code, we could
> just change the expansion to repeat the argument.

I like this stuff. 

So I'd prefer IS_GEN(dev_priv, 2) in favor of IS_GEN2(dev_priv)
throughout.

As long as it doesn't increase the code size too much, but this being
macro magic I don't think it should.

Care to cook up a patch against current tip to make IS_GEN() take 1 or 2
args? If I read the above right, you'll get a build error for using
IS_GEN(dev_priv, 1, 2, 3), is that correct?

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Graphics Center
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