Add GM passive safety mode (#266)

VERSION

@@ -1 +1 @@
-v1.4.6
+v1.4.7

board/safety.h

@@ -8,6 +8,7 @@
 #include "safety/safety_tesla.h"
 #include "safety/safety_gm_ascm.h"
 #include "safety/safety_gm.h"
+#include "safety/safety_gm_passive.h"
 #include "safety/safety_ford.h"
 #include "safety/safety_cadillac.h"
 #include "safety/safety_hyundai.h"
@@ -55,6 +56,7 @@ typedef struct {
 #define SAFETY_TESLA 8U
 #define SAFETY_CHRYSLER 9U
 #define SAFETY_SUBARU 10U
+#define SAFETY_GM_PASSIVE 11U
 #define SAFETY_GM_ASCM 0x1334U
 #define SAFETY_TOYOTA_IPAS 0x1335U
 #define SAFETY_ALLOUTPUT 0x1337U
@@ -72,6 +74,7 @@ const safety_hook_config safety_hook_registry[] = {
   {SAFETY_CHRYSLER, &chrysler_hooks},
   {SAFETY_SUBARU, &subaru_hooks},
   {SAFETY_TOYOTA_IPAS, &toyota_ipas_hooks},
+  {SAFETY_GM_PASSIVE, &gm_passive_hooks},
   {SAFETY_GM_ASCM, &gm_ascm_hooks},
   {SAFETY_TESLA, &tesla_hooks},
   {SAFETY_ALLOUTPUT, &alloutput_hooks},

board/safety/safety_gm_passive.h

@@ -0,0 +1,22 @@
+// All sending is disallowed.
+// The only difference from "no output" model
+// is using GM ignition hook.
+
+static void gm_passive_rx_hook(CAN_FIFOMailBox_TypeDef *to_push) {
+  int bus_number = GET_BUS(to_push);
+  int addr = GET_ADDR(to_push);
+
+  if ((addr == 0x1F1) && (bus_number == 0)) {
+    bool ign = (GET_BYTE(to_push, 0) & 0x20) != 0;
+    gm_ignition_started = ign;
+  }
+}
+
+const safety_hooks gm_passive_hooks = {
+  .init = gm_init,
+  .rx = gm_passive_rx_hook,
+  .tx = nooutput_tx_hook,
+  .tx_lin = nooutput_tx_lin_hook,
+  .ignition = gm_ign_hook,
+  .fwd = default_fwd_hook,
+};