diff --git a/input/input_binary.c b/input/input_binary.c
index 2f1462d0..ef9bddcb 100644
--- a/input/input_binary.c
+++ b/input/input_binary.c
@@ -17,6 +17,7 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <stdlib.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
@@ -24,52 +25,75 @@
 #include <sys/time.h>
 #include <sigrok.h>
 
-#define CHUNKSIZE 4096
+#define CHUNKSIZE          4096
+#define DEFAULT_NUM_PROBES    8
+
 
 static int format_match(const char *filename)
 {
+
+	/* suppress compiler warning */
 	filename = NULL;
+
+	/* this module will handle anything you throw at it */
 	return TRUE;
 }
 
-static int in_loadfile(const char *filename)
+static int init(struct input *in)
+{
+	int num_probes;
+
+	if (in->param && in->param[0]) {
+		num_probes = strtoul(in->param, NULL, 10);
+		if (num_probes < 1)
+			return SIGROK_ERR;
+	} else
+		num_probes = DEFAULT_NUM_PROBES;
+
+	/* create a virtual device */
+	in->vdevice = device_new(NULL, 0, num_probes);
+
+	return SIGROK_OK;
+}
+
+static int loadfile(struct input *in, const char *filename)
 {
 	struct datafeed_header header;
 	struct datafeed_packet packet;
-	struct device *device;
 	char buffer[CHUNKSIZE];
 	int fd, size, num_probes;
 
 	if ((fd = open(filename, O_RDONLY)) == -1)
 		return SIGROK_ERR;
 
-	/* TODO: Number of probes is hardcoded to 8. */
-	num_probes = 8;
-	device = device_new(NULL, 0, num_probes);
+	num_probes = g_slist_length(in->vdevice->probes);
 
+	/* send header */
 	header.feed_version = 1;
 	header.num_logic_probes = num_probes;
-	header.num_analog_probes = 0; /* FIXME */
+	header.num_analog_probes = 0;
 	header.protocol_id = PROTO_RAW;
 	header.samplerate = 0;
 	gettimeofday(&header.starttime, NULL);
 	packet.type = DF_HEADER;
 	packet.length = sizeof(struct datafeed_header);
 	packet.payload = &header;
-	session_bus(device, &packet);
+	session_bus(in->vdevice, &packet);
 
+	/* chop up the input file into chunks and feed it into the session bus */
 	packet.type = DF_LOGIC;
-	packet.unitsize = 1;
+	packet.unitsize = (num_probes + 7) / 8;
 	packet.payload = buffer;
 	while ((size = read(fd, buffer, CHUNKSIZE)) > 0) {
 		packet.length = size;
-		session_bus(device, &packet);
+		session_bus(in->vdevice, &packet);
 	}
 	close(fd);
 
+	/* end of stream */
 	packet.type = DF_END;
 	packet.length = 0;
-	session_bus(device, &packet);
+	session_bus(in->vdevice, &packet);
 
 	return SIGROK_OK;
 }
@@ -78,5 +102,6 @@ struct input_format input_binary = {
 	"binary",
 	"Raw binary",
 	format_match,
-	in_loadfile,
+	init,
+	loadfile,
 };
diff --git a/sigrok.h b/sigrok.h
index 496f1c6c..9a22cb0e 100644
--- a/sigrok.h
+++ b/sigrok.h
@@ -123,15 +123,16 @@ struct datafeed_header {
 
 struct input {
 	struct input_format *format;
-	void *param;
-	void *internal;
+	char *param;
+	struct device *vdevice;
 };
 
 struct input_format {
 	char *extension;
 	char *description;
 	int (*format_match) (const char *filename);
-	int (*in_loadfile) (const char *filename);
+	int (*init) (struct input *in);
+	int (*loadfile) (struct input *in, const char *filename);
 };