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: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Cc: Martin Bugge <marbugge@xxxxxxxxx>
Signed-off-by: Prashant Laddha <prladdha@xxxxxxxxx>
---
drivers/media/v4l2-core/v4l2-dv-timings.c | 30 ++++++++++++++++++++----------
1 file changed, 20 insertions(+), 10 deletions(-)
diff --git a/drivers/media/v4l2-core/v4l2-dv-timings.c b/drivers/media/v4l2-core/v4l2-dv-timings.c
index 86e11d1..3e14dc4 100644
--- a/drivers/media/v4l2-core/v4l2-dv-timings.c
+++ b/drivers/media/v4l2-core/v4l2-dv-timings.c
@@ -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");
@@ -572,16 +573,25 @@ 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;
+ u64 den;
+
+ num = ((image_width * GTF_D_C_PRIME * (u64)hfreq) -
+ ((u64)image_width * GTF_D_M_PRIME * 1000));
+ den = ((u64)hfreq * (100 - GTF_D_C_PRIME) +
+ GTF_D_M_PRIME * 1000);
+ h_blank = div_u64((num + (den >> 1)), den);
+ } else {
+ u64 num;
+ u64 den;
+
+ num = ((image_width * GTF_S_C_PRIME * (u64)hfreq) -
+ ((u64)image_width * GTF_S_M_PRIME * 1000));
+ den = ((u64)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);
--
1.9.1
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