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media: v4l2-dv-timings: Introduce v4l2_calc_timeperframe helper 

A new helper function was introduced to facilitate the calculation
of time per frame value whenever we have access to the full
v4l2_dv_timings structure.

This should be used only for receivers and only when there is
enough accuracy in the measured pixel clock value as well as in
the horizontal/vertical values.

Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
This commit is contained in:
Jose Abreu 2017-03-21 07:49:17 -04:00 committed by Mauro Carvalho Chehab
parent f992cee5ef
commit 87f9ed85d0
2 changed files with 50 additions and 0 deletions
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39
drivers/media/v4l2-core/v4l2-dv-timings.c
View File

@ -373,6 +373,45 @@ struct v4l2_fract v4l2_dv_timings_aspect_ratio(const struct v4l2_dv_timings *t)
}
EXPORT_SYMBOL_GPL(v4l2_dv_timings_aspect_ratio);
/** v4l2_calc_timeperframe - helper function to calculate timeperframe based
* v4l2_dv_timings fields.
* @t - Timings for the video mode.
*
* Calculates the expected timeperframe using the pixel clock value and
* horizontal/vertical measures. This means that v4l2_dv_timings structure
* must be correctly and fully filled.
*/
struct v4l2_fract v4l2_calc_timeperframe(const struct v4l2_dv_timings *t)
{
const struct v4l2_bt_timings *bt = &t->bt;
struct v4l2_fract fps_fract = { 1, 1 };
unsigned long n, d;
u32 htot, vtot, fps;
u64 pclk;
if (t->type != V4L2_DV_BT_656_1120)
return fps_fract;
htot = V4L2_DV_BT_FRAME_WIDTH(bt);
vtot = V4L2_DV_BT_FRAME_HEIGHT(bt);
pclk = bt->pixelclock;
if ((bt->flags & V4L2_DV_FL_CAN_DETECT_REDUCED_FPS) &&
(bt->flags & V4L2_DV_FL_REDUCED_FPS))
pclk = div_u64(pclk * 1000ULL, 1001);
fps = (htot * vtot) > 0 ? div_u64((100 * pclk), (htot * vtot)) : 0;
if (!fps)
return fps_fract;
rational_best_approximation(fps, 100, fps, 100, &n, &d);
fps_fract.numerator = d;
fps_fract.denominator = n;
return fps_fract;
}
EXPORT_SYMBOL_GPL(v4l2_calc_timeperframe);
/*
* CVT defines
* Based on Coordinated Video Timings Standard

11
include/media/v4l2-dv-timings.h
View File

@ -10,6 +10,17 @@
#include <linux/videodev2.h>
/**
* v4l2_calc_timeperframe - helper function to calculate timeperframe based
* v4l2_dv_timings fields.
* @t: Timings for the video mode.
*
* Calculates the expected timeperframe using the pixel clock value and
* horizontal/vertical measures. This means that v4l2_dv_timings structure
* must be correctly and fully filled.
*/
struct v4l2_fract v4l2_calc_timeperframe(const struct v4l2_dv_timings *t);
/*
* v4l2_dv_timings_presets: list of all dv_timings presets.
*/