2 files changed, 23 insertions, 0 deletions

diff --git a/include/mtdev.h b/include/mtdev.h
index 5f2f6a3..e2fdc9d 100644
--- a/include/mtdev.h
+++ b/include/mtdev.h
@@ -146,6 +146,17 @@ int mtdev_configure(struct mtdev *dev, int fd);
 int mtdev_open(struct mtdev *dev, int fd);
 
 /**
+ * mtdev_idle - check state of kernel device
+ * @dev: the mtdev in use
+ * @fd: file descriptor of the kernel device
+ * @ms: number of milliseconds to wait for activity
+ *
+ * Returns true if the device is idle, i.e., there are no buffered
+ * events and there is nothing to fetch from the kernel device.
+ */
+int mtdev_idle(struct mtdev *dev, int fd, int ms);
+
+/**
  * mtdev_fetch - fetch an event from the kernel device
  * @dev: the mtdev in use
  * @ev: the kernel input event to fill
diff --git a/src/iobuf.c b/src/iobuf.c
index 6d238ec..83e531a 100644
--- a/src/iobuf.c
+++ b/src/iobuf.c
@@ -28,6 +28,18 @@
 
 #include "iobuf.h"
 #include "state.h"
+#include <poll.h>
+
+int mtdev_idle(struct mtdev *dev, int fd, int ms)
+{
+        struct mtdev_state *state = dev->state;
+        struct mtdev_iobuf *buf = &state->iobuf;
+        struct pollfd fds = { fd, POLLIN, 0 };
+        return evbuf_empty(&state->outbuf) &&
+                evbuf_empty(&state->inbuf) &&
+                buf->head == buf->tail &&
+                poll(&fds, 1, ms) <= 0;
+}
 
 int mtdev_fetch(struct mtdev *dev, struct input_event *ev, int fd)
 {