Many video drivers implement a discrete set of frame formats and thus face
a task of finding the best match for a user-requested format. Implementing
this in a generic function has also an advantage, that different drivers
with similar supported format sets will select the same format for the
user, which improves consistency across drivers.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
---
I'm currently away from my hardware, so, this is only compile tested and
run-time tested with a test application. In any case, reviews and
suggestions welcome.
drivers/media/video/v4l2-common.c | 26 ++++++++++++++++++++++++++
include/linux/videodev2.h | 10 ++++++++++
2 files changed, 36 insertions(+), 0 deletions(-)
diff --git a/drivers/media/video/v4l2-common.c b/drivers/media/video/v4l2-common.c
index 4e53b0b..90727e6 100644
--- a/drivers/media/video/v4l2-common.c
+++ b/drivers/media/video/v4l2-common.c
@@ -1144,3 +1144,29 @@ int v4l_fill_dv_preset_info(u32 preset, struct v4l2_dv_enum_preset *info)
return 0;
}
EXPORT_SYMBOL_GPL(v4l_fill_dv_preset_info);
+
+struct v4l2_frmsize_discrete *v4l2_find_nearest_format(struct v4l2_discrete_probe *probe,
+ s32 width, s32 height)
+{
+ int i;
+ u32 error, min_error = ~0;
+ struct v4l2_frmsize_discrete *size, *best = NULL;
+
+ if (!probe)
+ return best;
+
+ for (i = 0, size = probe->sizes; i < probe->num_sizes; i++, size++) {
+ if (probe->probe && !probe->probe(probe))
+ continue;
+ error = abs(size->width - width) + abs(size->height - height);
+ if (error < min_error) {
+ min_error = error;
+ best = size;
+ }
+ if (!error)
+ break;
+ }
+
+ return best;
+}
+EXPORT_SYMBOL_GPL(v4l2_find_nearest_format);
diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
index 047f7e6..f622bba 100644
--- a/include/linux/videodev2.h
+++ b/include/linux/videodev2.h
@@ -394,6 +394,16 @@ struct v4l2_frmsize_discrete {
__u32 height; /* Frame height [pixel] */
};
+struct v4l2_discrete_probe {
+ struct v4l2_frmsize_discrete *sizes;
+ int num_sizes;
+ void *priv;
+ bool (*probe)(struct v4l2_discrete_probe *);
+};
+
+struct v4l2_frmsize_discrete *v4l2_find_nearest_format(struct v4l2_discrete_probe *probe,
+ s32 width, s32 height);
+
struct v4l2_frmsize_stepwise {
__u32 min_width; /* Minimum frame width [pixel] */
__u32 max_width; /* Maximum frame width [pixel] */
--
1.5.6
--
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