diff --git a/libril/ril.cpp b/libril/ril.cpp
index 944c860..f31c516 100644
--- a/libril/ril.cpp
+++ b/libril/ril.cpp
@@ -2372,12 +2372,12 @@
             break;
         case 3:
             LOGI ("Debug port: QXDM log enable.");
-            qxdm_data[0] = 65536;
-            qxdm_data[1] = 16;
-            qxdm_data[2] = 1;
-            qxdm_data[3] = 32;
-            qxdm_data[4] = 0;
-            qxdm_data[4] = 8;
+            qxdm_data[0] = 65536;     // head.func_tag
+            qxdm_data[1] = 16;        // head.len
+            qxdm_data[2] = 1;         // mode: 1 for 'start logging'
+            qxdm_data[3] = 32;        // log_file_size: 32megabytes
+            qxdm_data[4] = 0;         // log_mask
+            qxdm_data[5] = 8;         // log_max_fileindex
             issueLocalRequest(RIL_REQUEST_OEM_HOOK_RAW, qxdm_data,
                               6 * sizeof(int));
             break;
@@ -2385,10 +2385,10 @@
             LOGI ("Debug port: QXDM log disable.");
             qxdm_data[0] = 65536;
             qxdm_data[1] = 16;
-            qxdm_data[2] = 0;
+            qxdm_data[2] = 0;          // mode: 0 for 'stop logging'
             qxdm_data[3] = 32;
             qxdm_data[4] = 0;
-            qxdm_data[4] = 8;
+            qxdm_data[5] = 8;
             issueLocalRequest(RIL_REQUEST_OEM_HOOK_RAW, qxdm_data,
                               6 * sizeof(int));
             break;