rfkill: move wait_for_initialized() to shared/

The function interface is the same, except that the output pointer may be NULL.

The implementation is slightly simplified by taking advantage of changes in
ancestor commit 'sd-device: attempt to read db again if it wasn't found', by
not creating a new sd_device object before re-checking the is_initialized
status.

v2:
- In v1, the old object was always used and the device received back from the
  sd_device_monitor_start callback was ignored. I *think* the result will be
  equivalent in both cases, because by the time we the callback gets called,
  the db entry in the filesystem will also exist, and any subsequent access to
  properties of the object would trigger a read of the database from disk. But
  I'm not certain, and anyway, using the device object received in the callback
  seems cleaner.

1 files changed, 78 insertions, 0 deletions

diff --git a/src/shared/udev-util.c b/src/shared/udev-util.c
index fdeaf8f613..4200032b3b 100644
--- a/src/shared/udev-util.c
+++ b/src/shared/udev-util.c
@@ -91,3 +91,81 @@ int udev_parse_config_full(
 
         return 0;
 }
+
+struct DeviceMonitorData {
+        const char *sysname;
+        sd_device *device;
+};
+
+static int device_monitor_handler(sd_device_monitor *monitor, sd_device *device, void *userdata) {
+        struct DeviceMonitorData *data = userdata;
+        const char *sysname;
+
+        assert(device);
+        assert(data);
+        assert(data->sysname);
+        assert(!data->device);
+
+        if (sd_device_get_sysname(device, &sysname) >= 0 && streq(sysname, data->sysname)) {
+                data->device = sd_device_ref(device);
+                return sd_event_exit(sd_device_monitor_get_event(monitor), 0);
+        }
+
+        return 0;
+}
+
+int device_wait_for_initialization(sd_device *device, const char *subsystem, sd_device **ret) {
+        _cleanup_(sd_device_monitor_unrefp) sd_device_monitor *monitor = NULL;
+        _cleanup_(sd_event_unrefp) sd_event *event = NULL;
+        struct DeviceMonitorData data = {};
+        int r;
+
+        assert(device);
+        assert(subsystem);
+
+        if (sd_device_get_is_initialized(device) > 0) {
+                if (ret)
+                        *ret = sd_device_ref(device);
+                return 0;
+        }
+
+        assert_se(sd_device_get_sysname(device, &data.sysname) >= 0);
+
+        /* Wait until the device is initialized, so that we can get access to the ID_PATH property */
+
+        r = sd_event_default(&event);
+        if (r < 0)
+                return log_error_errno(r, "Failed to get default event: %m");
+
+        r = sd_device_monitor_new(&monitor);
+        if (r < 0)
+                return log_error_errno(r, "Failed to acquire monitor: %m");
+
+        r = sd_device_monitor_filter_add_match_subsystem_devtype(monitor, subsystem, NULL);
+        if (r < 0)
+                return log_error_errno(r, "Failed to add %s subsystem match to monitor: %m", subsystem);
+
+        r = sd_device_monitor_attach_event(monitor, event);
+        if (r < 0)
+                return log_error_errno(r, "Failed to attach event to device monitor: %m");
+
+        r = sd_device_monitor_start(monitor, device_monitor_handler, &data);
+        if (r < 0)
+                return log_error_errno(r, "Failed to start device monitor: %m");
+
+        /* Check again, maybe things changed. Udev will re-read the db if the device wasn't initialized
+         * yet. */
+        if (sd_device_get_is_initialized(device) > 0) {
+                if (ret)
+                        *ret = sd_device_ref(device);
+                return 0;
+        }
+
+        r = sd_event_loop(event);
+        if (r < 0)
+                return log_error_errno(r, "Event loop failed: %m");
+
+        if (ret)
+                *ret = TAKE_PTR(data.device);
+        return 0;
+}