[PATCH 2/3] [media] v4l2-dv-timings: Introduce v4l2_calc_timeperframe helper

Jose Abreu
2017-03-21T11:50:00Z

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>
Cc: Carlos Palminha <palminha@synopsys.com>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Hans Verkuil <hans.verkuil@cisco.com>
Cc: linux-media@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
drivers/media/v4l2-core/v4l2-dv-timings.c | 39 +++++++++++++++++++++++++++++++
include/media/v4l2-dv-timings.h | 11 +++++++++
2 files changed, 50 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-dv-timings.c b/drivers/media/v4l2-core/v4l2-dv-timings.c
index 5c8c49d..b7b39c2 100644
--- a/drivers/media/v4l2-core/v4l2-dv-timings.c
+++ b/drivers/media/v4l2-core/v4l2-dv-timings.c
@@ -814,3 +814,42 @@ struct v4l2_fract v4l2_calc_aspect_ratio(u8 hor_landscape, u8 vert_portrait)
return aspect;
}
EXPORT_SYMBOL_GPL(v4l2_calc_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);
diff --git a/include/media/v4l2-dv-timings.h b/include/media/v4l2-dv-timings.h
index 61a1889..c1eef08 100644
--- a/include/media/v4l2-dv-timings.h
+++ b/include/media/v4l2-dv-timings.h
@@ -203,6 +203,17 @@ bool v4l2_detect_gtf(unsigned frame_height, unsigned hfreq, unsigned vsync,
*/
struct v4l2_fract v4l2_dv_timings_aspect_ratio(const struct v4l2_dv_timings *t);

+/**
+ * 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);
+
/*
* reduce_fps - check if conditions for reduced fps are true.
* bt - v4l2 timing structure
--
1.9.1