header: Update documentation for hid_get_feature_report()

hidapi/hidapi.h

@@ -293,22 +293,26 @@ extern "C" {
 
 		/** @brief Get a feature report from a HID device.
 
-			Make sure to set the first byte of @p data[] to the Report
-			ID of the report to be read.  Make sure to allow space for
-			this extra byte in @p data[].
+			Set the first byte of @p data[] to the Report ID of the
+			report to be read.  Make sure to allow space for this
+			extra byte in @p data[]. Upon return, the first byte will
+			still contain the Report ID, and the report data will
+			start in data[1].
 
 			@ingroup API
 			@param device A device handle returned from hid_open().
 			@param data A buffer to put the read data into, including
 				the Report ID. Set the first byte of @p data[] to the
-				Report ID of the report to be read.
+				Report ID of the report to be read, or set it to zero
+				if your device does not use numbered reports.
 			@param length The number of bytes to read, including an
 				extra byte for the report ID. The buffer can be longer
 				than the actual report.
 
 			@returns
-				This function returns the number of bytes read and
-				-1 on error.
+				This function returns the number of bytes read plus
+				one for the report ID (which is still in the first
+				byte), or -1 on error.
 		*/
 		int HID_API_EXPORT HID_API_CALL hid_get_feature_report(hid_device *device, unsigned char *data, size_t length);