lavd/v4l2enc: check write return value.

libavdevice/v4l2enc.c

@@ -85,7 +85,8 @@ static av_cold int write_header(AVFormatContext *s1)
 static int write_packet(AVFormatContext *s1, AVPacket *pkt)
 {
     const V4L2Context *s = s1->priv_data;
-    write(s->fd, pkt->data, pkt->size);
+    if (write(s->fd, pkt->data, pkt->size) == -1)
+        return AVERROR(errno);
     return 0;
 }