Commit c9bc9f50 authored by Prashant Laddha's avatar Prashant Laddha Committed by Mauro Carvalho Chehab

[media] v4l2-dv-timings: fix overflow in gtf timings calculation

The intermediate calculation in the expression for hblank can exceed
32 bit signed range. This overflow can lead to negative values for
hblank. Typecasting intermediate variable to higher precision.

Cc: Martin Bugge <marbugge@cisco.com>
Signed-off-by: default avatarPrashant Laddha <prladdha@cisco.com>
[hans.verkuil@cisco.com: made the denominator u32, since that's what div_u64 expects]
Signed-off-by: default avatarHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@osg.samsung.com>
parent ed1bc664
......@@ -25,6 +25,7 @@
#include <linux/videodev2.h>
#include <linux/v4l2-dv-timings.h>
#include <media/v4l2-dv-timings.h>
#include <linux/math64.h>
MODULE_AUTHOR("Hans Verkuil");
MODULE_DESCRIPTION("V4L2 DV Timings Helper Functions");
......@@ -554,16 +555,23 @@ bool v4l2_detect_gtf(unsigned frame_height,
image_width = (image_width + GTF_CELL_GRAN/2) & ~(GTF_CELL_GRAN - 1);
/* Horizontal */
if (default_gtf)
h_blank = ((image_width * GTF_D_C_PRIME * hfreq) -
(image_width * GTF_D_M_PRIME * 1000) +
(hfreq * (100 - GTF_D_C_PRIME) + GTF_D_M_PRIME * 1000) / 2) /
(hfreq * (100 - GTF_D_C_PRIME) + GTF_D_M_PRIME * 1000);
else
h_blank = ((image_width * GTF_S_C_PRIME * hfreq) -
(image_width * GTF_S_M_PRIME * 1000) +
(hfreq * (100 - GTF_S_C_PRIME) + GTF_S_M_PRIME * 1000) / 2) /
(hfreq * (100 - GTF_S_C_PRIME) + GTF_S_M_PRIME * 1000);
if (default_gtf) {
u64 num;
u32 den;
num = ((image_width * GTF_D_C_PRIME * (u64)hfreq) -
((u64)image_width * GTF_D_M_PRIME * 1000));
den = hfreq * (100 - GTF_D_C_PRIME) + GTF_D_M_PRIME * 1000;
h_blank = div_u64((num + (den >> 1)), den);
} else {
u64 num;
u32 den;
num = ((image_width * GTF_S_C_PRIME * (u64)hfreq) -
((u64)image_width * GTF_S_M_PRIME * 1000));
den = hfreq * (100 - GTF_S_C_PRIME) + GTF_S_M_PRIME * 1000;
h_blank = div_u64((num + (den >> 1)), den);
}
h_blank = ((h_blank + GTF_CELL_GRAN) / (2 * GTF_CELL_GRAN)) *
(2 * GTF_CELL_GRAN);
......
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