core: allow building and running without udev

Instead of relying on the udev daemon and GUDev to manage the devices reported
by the kernel, we can now run ModemManager relying solely on the kernel events
reported via the new ReportKernelEvent() API. Therefore, the '--no-auto-scan'
option is implicit for the ModemManager daemon when udev is disabled in the
build.

Additionally, a new custom implementation of the kernel device object is
provided, which uses sysfs to load the properties and attributes required in
each kernel device, instead of using a GUdevDevice.

The udev rule files are kept in place, and a simple custom parser is provided
which preloads all rules in memory once and then applies them to the different
kernel objects reported via ReportKernelEvent(), e.g. to set port type hints.
A simple unit test setup is prepared to validate the udev rules during the
`check' Makefile target.

cli/mmcli-manager.c

@@ -29,7 +29,9 @@
 #include <glib.h>
 #include <gio/gio.h>
 
-#include <gudev/gudev.h>
+#if WITH_UDEV
+# include <gudev/gudev.h>
+#endif
 
 #define _LIBMM_INSIDE_MMCLI
 #include "libmm-glib.h"
@@ -41,7 +43,9 @@
 typedef struct {
     MMManager *manager;
     GCancellable *cancellable;
+#if WITH_UDEV
     GUdevClient *udev;
+#endif
 } Context;
 static Context *ctx;
 
@@ -51,7 +55,10 @@ static gboolean monitor_modems_flag;
 static gboolean scan_modems_flag;
 static gchar *set_logging_str;
 static gchar *report_kernel_event_str;
+
+#if WITH_UDEV
 static gboolean report_kernel_event_auto_scan;
+#endif
 
 static GOptionEntry entries[] = {
     { "set-logging", 'G', 0, G_OPTION_ARG_STRING, &set_logging_str,
@@ -74,10 +81,12 @@ static GOptionEntry entries[] = {
       "Report kernel event",
       "[\"key=value,...\"]"
     },
+#if WITH_UDEV
     { "report-kernel-event-auto-scan", 0, 0, G_OPTION_ARG_NONE, &report_kernel_event_auto_scan,
       "Automatically report kernel events based on udev notifications",
       NULL
     },
+#endif
     { NULL }
 };
 
@@ -110,8 +119,11 @@ mmcli_manager_options_enabled (void)
                  monitor_modems_flag +
                  scan_modems_flag +
                  !!set_logging_str +
-                 !!report_kernel_event_str +
-                 report_kernel_event_auto_scan);
+                 !!report_kernel_event_str);
+
+#if WITH_UDEV
+    n_actions += report_kernel_event_auto_scan;
+#endif
 
     if (n_actions > 1) {
         g_printerr ("error: too many manager actions requested\n");
@@ -121,8 +133,10 @@ mmcli_manager_options_enabled (void)
     if (monitor_modems_flag)
         mmcli_force_async_operation ();
 
+#if WITH_UDEV
     if (report_kernel_event_auto_scan)
         mmcli_force_async_operation ();
+#endif
 
     checked = TRUE;
     return !!n_actions;
@@ -134,8 +148,11 @@ context_free (Context *ctx)
     if (!ctx)
         return;
 
+#if WITH_UDEV
     if (ctx->udev)
         g_object_unref (ctx->udev);
+#endif
+
     if (ctx->manager)
         g_object_unref (ctx->manager);
     if (ctx->cancellable)
@@ -308,6 +325,8 @@ cancelled (GCancellable *cancellable)
     mmcli_async_operation_done ();
 }
 
+#if WITH_UDEV
+
 static void
 handle_uevent (GUdevClient *client,
                const char  *action,
@@ -324,6 +343,8 @@ handle_uevent (GUdevClient *client,
     g_object_unref (properties);
 }
 
+#endif
+
 static void
 get_manager_ready (GObject      *source,
                    GAsyncResult *result,
@@ -367,6 +388,7 @@ get_manager_ready (GObject      *source,
         return;
     }
 
+#if WITH_UDEV
     if (report_kernel_event_auto_scan) {
         const gchar *subsys[] = { "tty", "usbmisc", "net", NULL };
         guint i;
@@ -400,6 +422,7 @@ get_manager_ready (GObject      *source,
                                NULL);
         return;
     }
+#endif
 
     /* Request to monitor modems? */
     if (monitor_modems_flag) {
@@ -457,10 +480,12 @@ mmcli_manager_run_synchronous (GDBusConnection *connection)
         exit (EXIT_FAILURE);
     }
 
+#if WITH_UDEV
     if (report_kernel_event_auto_scan) {
         g_printerr ("error: monitoring udev events cannot be done synchronously\n");
         exit (EXIT_FAILURE);
     }
+#endif
 
     /* Initialize context */
     ctx = g_new0 (Context, 1);