On 05/02/2015 07:23 PM, Prashant Laddha wrote: > 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 | 16 ++++++++-------- > 1 file changed, 8 insertions(+), 8 deletions(-) > > diff --git a/drivers/media/v4l2-core/v4l2-dv-timings.c b/drivers/media/v4l2-core/v4l2-dv-timings.c > index 86e11d1..9d27f05 100644 > --- a/drivers/media/v4l2-core/v4l2-dv-timings.c > +++ b/drivers/media/v4l2-core/v4l2-dv-timings.c > @@ -573,15 +573,15 @@ bool v4l2_detect_gtf(unsigned frame_height, > > /* 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); > + h_blank = ((image_width * GTF_D_C_PRIME * (long long)hfreq) - > + ((long long)image_width * GTF_D_M_PRIME * 1000) + > + ((long long)hfreq * (100 - GTF_D_C_PRIME) + GTF_D_M_PRIME * 1000) / 2) / > + ((long long)hfreq * (100 - GTF_D_C_PRIME) + GTF_D_M_PRIME * 1000); This will not work on systems that cannot divide 64 bit numbers. Use the do_div function for this. It's a common mistake to make when developing on Intel CPUs. Been there, done that :-) Multiple times, in fact... And I think it will help a lot if some additional variables are introduced since this calculation is getting complex. Also replace "/ 2" by ">> 1". That will guarantee that you do not need do_div for that. Probably unnecessary since I would expect gcc to be smart enough to replace / 2 by >> 1 anyway, but it doesn't hurt. Regards, Hans > 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); > + h_blank = ((image_width * GTF_S_C_PRIME * (long long)hfreq) - > + ((long long)image_width * GTF_S_M_PRIME * 1000) + > + ((long long)hfreq * (100 - GTF_S_C_PRIME) + GTF_S_M_PRIME * 1000) / 2) / > + ((long long)hfreq * (100 - GTF_S_C_PRIME) + GTF_S_M_PRIME * 1000); > > h_blank = ((h_blank + GTF_CELL_GRAN) / (2 * GTF_CELL_GRAN)) * > (2 * GTF_CELL_GRAN); > -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
