v4l2: Query buffer sizes when exporting buffers

In order to properly import buffers, the size of each buffer to be
imported must be known. The size is queried when the buffers are
mmap()ed, but mapping them isn't mandatory. Query the size when
exporting buffers to ensure that we always have a valid size for import.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 14 insertions, 1 deletions

diff --git a/v4l2.c b/v4l2.c
index 25c8fb4..6b1c753 100644
--- a/v4l2.c
+++ b/v4l2.c
@@ -631,13 +631,26 @@ int v4l2_export_buffers(struct v4l2_device *dev)
 			.type = dev->type,
 			.index = i,
 		};
+		struct v4l2_buffer buf = {
+			.index = i,
+			.type = dev->type,
+			.memory = dev->memtype,
+		};
+
+		ret = ioctl(dev->fd, VIDIOC_QUERYBUF, &buf);
+		if (ret < 0) {
+			printf("%s: unable to query buffer %u (%d).\n",
+			       dev->name, i, errno);
+			return -errno;
+		}
 
 		ret = ioctl(dev->fd, VIDIOC_EXPBUF, &expbuf);
 		if (ret < 0) {
 			printf("Failed to export buffer %u.\n", i);
-			return ret;
+			return -errno;
 		}
 
+		dev->buffers[i].size = buf.length;
 		dev->buffers[i].dmabuf = expbuf.fd;
 
 		printf("%s: buffer %u exported with fd %u.\n",