Commit 7f415408 authored Mar 17, 2015 by Krishna Chaitanya Parimi Committed by Gerrit - the friendly Code Review server Dec 29, 2015

msm: mdss: alter linear_map to incorporate rounding for AD



The helper function linear_map would take the integral part
of the calculated map, thereby causing issues with getting
the same value after consecutive map and inverse map calls.

For ex: linear_map(21, out, 255, 4095) would translate to
        *out = 21 * 4095 / 255 = 337, whereas inverse case
        linear_map(337, out, 4095, 255) would translate to
        *out = 337 * 255 / 4095 = 20

Changing linear_map from ((in * out_max) / in_max) to a more
precise ((2 * (in * out_max) + in_max) / (2 * in_max)) for
incorporating rounding in the integral mapping.

Change-Id: I15cd8aa1326813ce3cb3a426cbb4e78374623c72
Signed-off-by: Krishna Chaitanya Parimi <cparimi@codeaurora.org>

parent acd5ad63

drivers/video/msm/mdss/mdss_mdp_pp.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -515,7 +515,7 @@ inline int linear_map(int in, int *out, int in_max, int out_max)
		{
		if (in < 0 \|\| !out \|\| in_max <= 0 \|\| out_max <= 0)
		return -EINVAL;
		out = ((in out_max) / in_max);
		out = ((2 (in * out_max) + in_max) / (2 * in_max));
		pr_debug("in = %d, out = %d, in_max = %d, out_max = %d\n",
		in, *out, in_max, out_max);
		if ((in > 0) && (*out == 0))