V4L/DVB (10237): pvrusb2: Generate a device-unique identifier

Implement a new internal function to create a string device
identifier.  This ID stays with the specific device, making it useful
to user space to identify specific devices.  We use the serial number
if available; otherwise we give up and just spit out a unit/instance ID.

Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/video/pvrusb2/pvrusb2-hdw.c b/drivers/media/video/pvrusb2/pvrusb2-hdw.c
index fa304e5..ac5dad0 100644
--- a/drivers/media/video/pvrusb2/pvrusb2-hdw.c
+++ b/drivers/media/video/pvrusb2/pvrusb2-hdw.c
@@ -1283,6 +1283,12 @@
 }
 
 
+const char *pvr2_hdw_get_device_identifier(struct pvr2_hdw *hdw)
+{
+	return hdw->identifier;
+}
+
+
 unsigned long pvr2_hdw_get_cur_freq(struct pvr2_hdw *hdw)
 {
 	return hdw->freqSelector ? hdw->freqValTelevision : hdw->freqValRadio;
@@ -2024,6 +2030,19 @@
 		hdw->std_mask_eeprom = V4L2_STD_ALL;
 	}
 
+	if (hdw->serial_number) {
+		idx = scnprintf(hdw->identifier, sizeof(hdw->identifier) - 1,
+				"sn-%lu", hdw->serial_number);
+	} else if (hdw->unit_number >= 0) {
+		idx = scnprintf(hdw->identifier, sizeof(hdw->identifier) - 1,
+				"unit-%c",
+				hdw->unit_number + 'a');
+	} else {
+		idx = scnprintf(hdw->identifier, sizeof(hdw->identifier) - 1,
+				"unit-??");
+	}
+	hdw->identifier[idx] = 0;
+
 	pvr2_hdw_setup_std(hdw);
 
 	if (!get_default_tuner_type(hdw)) {