[Intel-gfx] [PATCH 13/14] drm/i915: Use binary search when looking for shadowed registers

[Joonas Lahtinen]

On pe, 2016-09-30 at 19:08 +0100, Chris Wilson wrote:
> On Fri, Sep 30, 2016 at 06:48:48PM +0100, Tvrtko Ursulin wrote: 
> > +static int mmio_reg_cmp(const void *key, const void *elt)
> > +{
> > +	u32 offset = (u32)(unsigned long)key;
> > +	i915_reg_t *reg = (i915_reg_t *)elt;
> > +
> > +	if (offset < i915_mmio_reg_offset(*reg))
> > +		return -1;
> > +	else if (offset > i915_mmio_reg_offset(*reg))
> > +		return 1;
> > +	else
> > +		return 0;
> 
> There's no issue with using
> 
> 	return offset - i915_mmio_reg_offset(*reg)
> 
> here.
> 

Why not?

> > +	reg = bsearch((void *)(unsigned long)offset,
> > +		      (const void *)gen8_shadowed_regs,
> > +		      ARRAY_SIZE(gen8_shadowed_regs),
> > +		      sizeof(i915_reg_t),
> > +		      mmio_reg_cmp);
> > +
> > +	return reg;
> 
> Or just return bseearch() ? (Probably like this for easing future
> patches.)

Suggested that too, but obviously he has something in mind.

Regards, Joonas
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation