iface-modem: allow transitioning to the OFF power state

There are systems in which the modem power source can be controlled externally,
e.g. to switch it on or off. In these cases, it is sometimes advisable to be
able to tell the modem to cleanly shut off completely before the power is cut.
So, allow transitioning to the OFF power state if the modem supports it, even if
afterwards the modem could be completely unreachable.

src/mm-iface-modem.c

@@ -1703,12 +1703,28 @@ handle_set_power_state_auth_ready (MMBaseModem *self,
         return;
     }
 
-    /* Error if we're not in disabled state */
+    /* Only 'off', 'low' or 'up' expected */
+    if (ctx->power_state != MM_MODEM_POWER_STATE_LOW &&
+        ctx->power_state != MM_MODEM_POWER_STATE_ON &&
+        ctx->power_state != MM_MODEM_POWER_STATE_OFF) {
+        g_dbus_method_invocation_return_error (ctx->invocation,
+                                               MM_CORE_ERROR,
+                                               MM_CORE_ERROR_INVALID_ARGS,
+                                               "Cannot set '%s' power state",
+                                               mm_modem_power_state_get_string (ctx->power_state));
+        handle_set_power_state_context_free (ctx);
+        return;
+    }
+
     modem_state = MM_MODEM_STATE_UNKNOWN;
     g_object_get (self,
                   MM_IFACE_MODEM_STATE, &modem_state,
                   NULL);
-    if (modem_state != MM_MODEM_STATE_DISABLED) {
+
+    /* Going into LOW or ON only allowed in disabled state */
+    if ((ctx->power_state == MM_MODEM_POWER_STATE_LOW ||
+         ctx->power_state == MM_MODEM_POWER_STATE_ON) &&
+        modem_state != MM_MODEM_STATE_DISABLED) {
         g_dbus_method_invocation_return_error (ctx->invocation,
                                                MM_CORE_ERROR,
                                                MM_CORE_ERROR_WRONG_STATE,
@@ -1717,14 +1733,15 @@ handle_set_power_state_auth_ready (MMBaseModem *self,
         return;
     }
 
-    /* Only 'low' or 'up' expected */
+    /* Going into OFF, only allowed if locked, disabled or failed */
-    if (ctx->power_state != MM_MODEM_POWER_STATE_LOW &&
+    if (ctx->power_state == MM_MODEM_POWER_STATE_OFF &&
-        ctx->power_state != MM_MODEM_POWER_STATE_ON) {
+        modem_state != MM_MODEM_STATE_FAILED &&
+        modem_state != MM_MODEM_STATE_LOCKED &&
+        modem_state != MM_MODEM_STATE_DISABLED) {
         g_dbus_method_invocation_return_error (ctx->invocation,
                                                MM_CORE_ERROR,
-                                               MM_CORE_ERROR_INVALID_ARGS,
+                                               MM_CORE_ERROR_WRONG_STATE,
-                                               "Cannot set '%s' power state",
+                                               "Cannot set power state: modem either enabled or initializing");
-                                               mm_modem_power_state_get_string (ctx->power_state));
         handle_set_power_state_context_free (ctx);
         return;
     }
@@ -3190,6 +3207,28 @@ modem_power_down_ready (MMIfaceModem *self,
     set_power_state_context_complete_and_free (ctx);
 }
 
+static void
+modem_power_off_ready (MMIfaceModem *self,
+                        GAsyncResult *res,
+                        SetPowerStateContext *ctx)
+{
+    GError *error = NULL;
+
+    MM_IFACE_MODEM_GET_INTERFACE (self)->modem_power_off_finish (self, res, &error);
+    if (error) {
+        /* If the real and cached ones are different, set the real one */
+        if (ctx->previous_cached_power_state != ctx->previous_real_power_state)
+            mm_gdbus_modem_set_power_state (ctx->skeleton, ctx->previous_real_power_state);
+        g_simple_async_result_take_error (ctx->result, error);
+    } else {
+        mm_info ("Modem powered off... may no longer be accessible");
+        mm_gdbus_modem_set_power_state (ctx->skeleton, ctx->power_state);
+        g_simple_async_result_set_op_res_gboolean (ctx->result, TRUE);
+    }
+
+    set_power_state_context_complete_and_free (ctx);
+}
+
 static void
 set_power_state (SetPowerStateContext *ctx)
 {
@@ -3205,11 +3244,42 @@ set_power_state (SetPowerStateContext *ctx)
         return;
     }
 
+    /* Don't allow trying to recover from a power off */
+    if (ctx->previous_real_power_state == MM_MODEM_POWER_STATE_OFF) {
+        g_simple_async_result_set_error (ctx->result,
+                                         MM_CORE_ERROR,
+                                         MM_CORE_ERROR_WRONG_STATE,
+                                         "Cannot recover from a power off");
+        set_power_state_context_complete_and_free (ctx);
+        return;
+    }
+
     /* Supported transitions:
-     * UNKNOWN|OFF|LOW --> ON
+     * UNKNOWN|LOW --> ON
      * ON --> LOW
+     * ON|LOW --> OFF
      */
 
+    /* Fully powering off the modem? */
+    if (ctx->power_state == MM_MODEM_POWER_STATE_OFF) {
+        /* Error if unsupported */
+        if (!MM_IFACE_MODEM_GET_INTERFACE (ctx->self)->modem_power_off ||
+            !MM_IFACE_MODEM_GET_INTERFACE (ctx->self)->modem_power_off_finish) {
+            g_simple_async_result_set_error (ctx->result,
+                                             MM_CORE_ERROR,
+                                             MM_CORE_ERROR_UNSUPPORTED,
+                                             "Powering off is not supported by this modem");
+            set_power_state_context_complete_and_free (ctx);
+            return;
+        }
+
+        MM_IFACE_MODEM_GET_INTERFACE (ctx->self)->modem_power_off (
+            MM_IFACE_MODEM (ctx->self),
+            (GAsyncReadyCallback)modem_power_off_ready,
+            ctx);
+        return;
+    }
+
     /* Going into low power mode? */
     if (ctx->power_state == MM_MODEM_POWER_STATE_LOW) {
         /* Error if unsupported */

src/mm-iface-modem.h

@@ -304,6 +304,13 @@ struct _MMIfaceModem {
                                          GAsyncResult *res,
                                          GError **error);
 
+    /* Asynchronous modem power-off operation */
+    void (*modem_power_off) (MMIfaceModem *self,
+                             GAsyncReadyCallback callback,
+                             gpointer user_data);
+    gboolean (*modem_power_off_finish) (MMIfaceModem *self,
+                                        GAsyncResult *res,
+                                        GError **error);
     /* Create SIM */
     void (*create_sim) (MMIfaceModem *self,
                         GAsyncReadyCallback callback,