Re: [PATCH 13/13] drm/i915: Use binary search when looking for shadowed registers

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On 30/09/2016 08:54, Joonas Lahtinen wrote:
On to, 2016-09-29 at 16:35 +0100, Tvrtko Ursulin wrote:
+static int mmio_reg_cmp(const void *key, const void *elt)
+ {
<SNIP>
+	if (offset < i915_mmio_reg_offset(*reg))
+		return -1;
+	else if (offset > i915_mmio_reg_offset(*reg))
+		return 1;
+	else
+		return 0;
I was about to suggest return a - b; but then realized it might
overflow. After a bit of searching, that is done in
regcache_default_cmp though. So not sure if it's a bug in there or did
I miss something. This is safe way at least.

  static bool is_gen8_shadowed(u32 offset)
  {
-	int i;
-	for (i = 0; i < ARRAY_SIZE(gen8_shadowed_regs); i++)
-		if (offset == gen8_shadowed_regs[i].reg)
-			return true;
+	i915_reg_t *reg;
-	return false;
+	reg = bsearch((void *)(unsigned long)offset,
(unsigned long) is not required, as we don't have sign bits to extend.

Gcc warns if I omit that.

+		      (const void *)gen8_shadowed_regs,
+		      ARRAY_SIZE(gen8_shadowed_regs),
+		      sizeof(i915_reg_t),
+		      mmio_reg_cmp);
+
+	return reg ? true : false;
As I previously learnt, no need to explicitly convert bool types
anymore, so this can just be return bsearch(...);

With the last two fixed,

I've done this one.

Reviewed-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>

Thanks!

Tvrtko

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