On Sun, Feb 9, 2020 at 11:27 AM Gregor Riepl [off-list ref] wrote:

quoted

-     for (i = 0; i < ARRAY_SIZE(gp2ap002_illuminance_table) - 1; i++) {
-             ill1 = &gp2ap002_illuminance_table[i];
-             ill2 = &gp2ap002_illuminance_table[i + 1];
-
-             if (res > ill2->curr)
-                     continue;
-             if ((res <= ill1->curr) && (res >= ill2->curr))
-                     break;

That seems like a really, really contrived way to do a table lookup.

(...)

And since res is linear, interpolation won't even be needed.

Sorry for my quick hack, patches welcome ;)

quoted

+     lux = int_pow(10, (res/10));
+     if (lux > INT_MAX) {
+             dev_err(gp2ap002->dev, "lux overflow, capped\n");
+             lux = INT_MAX;
      }

This is certainly better, but I wonder if it's worth the computational cost.

We don't do this much so certainly the linecount shrink is
worth it.

Also: It looks like int_pow doesn't saturate, so even though it uses 64bit
integer math, it might be better to move the range check before the calculation.

How do you mean I should be doing that without actually
doing the power calculation? (Maybe a dumb question but
math was never my best subject.)

Yours,
Linus Walleij