fpi-device: Introduce a properly defined fpi_device_emulation_mode_enabled()

Drivers may do some adjustments in test mode, initially we wanted to
reduce this to the minimum but the usage of `FP_DEVICE_EMULATION`
exploded, so move this instead into a properly defined variable that:
 - Uses GLib compiler optimizations
 - Is read just once per process
 - Cannot be misused

doc/libfprint-2-sections.txt

@@ -282,6 +282,7 @@ fpi_device_get_current_action
 fpi_device_retry_new
 fpi_device_error_new
 fpi_device_retry_new_msg
+fpi_device_emulation_mode_enabled
 fpi_device_error_new_msg
 fpi_device_get_driver_data
 fpi_device_get_enroll_data

libfprint/drivers/egismoc/egis_etu905.c

@@ -1567,7 +1567,7 @@ egis_etu905_probe (FpDevice *device)
       return;
     }
 
-  if (g_strcmp0 (g_getenv ("FP_DEVICE_EMULATION"), "1") == 0)
+  if (fpi_device_emulation_mode_enabled (device))
     serial = g_strdup ("emulated-device");
   else
     serial = g_usb_device_get_string_descriptor (usb_dev,

libfprint/drivers/egismoc/egismoc.c

@@ -1500,7 +1500,7 @@ egismoc_probe (FpDevice *device)
       return;
     }
 
-  if (g_strcmp0 (g_getenv ("FP_DEVICE_EMULATION"), "1") == 0)
+  if (fpi_device_emulation_mode_enabled (FP_DEVICE (device)))
     serial = g_strdup ("emulated-device");
   else
     serial = g_usb_device_get_string_descriptor (usb_dev,

libfprint/drivers/elan.c

@@ -557,7 +557,7 @@ capture_run_state (FpiSsm *ssm, FpDevice *dev)
       else
         {
           /* XXX: The timeout is emulated incorrectly, resulting in a zero byte read. */
-          if (g_strcmp0 (g_getenv ("FP_DEVICE_EMULATION"), "1") == 0)
+          if (fpi_device_emulation_mode_enabled (FP_DEVICE (self)))
             fpi_ssm_mark_completed (ssm);
           else
             fpi_ssm_mark_failed (ssm, fpi_device_error_new (FP_DEVICE_ERROR_PROTO));

libfprint/drivers/elanspi.c

@@ -94,7 +94,7 @@ static void
 elanspi_do_hwreset (FpiDeviceElanSpi *self, GError **err)
 {
   /* Skip in emulation mode, since we don't mock hid devices */
-  if (g_strcmp0 (g_getenv ("FP_DEVICE_EMULATION"), "1") == 0)
+  if (fpi_device_emulation_mode_enabled (FP_DEVICE (self)))
     return;
 
   /*
@@ -485,7 +485,8 @@ elanspi_capture_old_handler (FpiSsm *ssm, FpDevice *dev)
       if (!(self->sensor_status & 4))
         {
           /* has the timeout expired? -- disabled in testing since valgrind is very slow */
-          if (g_get_monotonic_time () > self->capture_timeout && g_strcmp0 (g_getenv ("FP_DEVICE_EMULATION"), "1") != 0)
+          if (g_get_monotonic_time () > self->capture_timeout &&
+              !fpi_device_emulation_mode_enabled (FP_DEVICE (self)))
             {
               /* end with a timeout */
               fpi_ssm_mark_failed (ssm, g_error_new (G_IO_ERROR, G_IO_ERROR_TIMED_OUT, "timed out waiting for new line"));

libfprint/drivers/goodixmoc/goodix.c

@@ -970,7 +970,7 @@ fp_enroll_sm_run_state (FpiSsm *ssm, FpDevice *device)
         user_id_len = MIN (100, user_id_len);
         finger = 1;
 
-        if (g_strcmp0 (g_getenv ("FP_DEVICE_EMULATION"), "1") == 0)
+        if (fpi_device_emulation_mode_enabled (FP_DEVICE (self)))
           memset (self->template_id, 0, TEMPLATE_ID_SIZE);
         uid = g_variant_new_fixed_array (G_VARIANT_TYPE_BYTE,
                                          user_id,
@@ -1390,7 +1390,7 @@ gx_fp_probe (FpDevice *device)
   if (!g_usb_device_claim_interface (usb_dev, 0, 0, &error))
     goto err_close;
 
-  if (g_strcmp0 (g_getenv ("FP_DEVICE_EMULATION"), "1") == 0)
+  if (fpi_device_emulation_mode_enabled (FP_DEVICE (self)))
     {
 
       serial = g_strdup ("emulated-device");

libfprint/drivers/mafpmoc/mafpmoc.c

@@ -2317,7 +2317,7 @@ mafp_probe (FpDevice *device)
   if (!g_usb_device_claim_interface (usb_dev, self->interface_num, 0, &error))
     goto err_close;
 
-  if (g_strcmp0 (g_getenv ("FP_DEVICE_EMULATION"), "1") == 0)
+  if (fpi_device_emulation_mode_enabled (device))
     {
       serial = g_strdup ("emulated-device");
     }
@@ -2378,7 +2378,7 @@ mafp_init (FpDevice *device)
   else
     fp_dbg ("device no storage");
 
-  if (g_strcmp0 (g_getenv ("FP_DEVICE_EMULATION"), "1") == 0)
+  if (fpi_device_emulation_mode_enabled (device))
     {
       serial = g_strdup ("emulated-device");
     }

libfprint/drivers/secugen.c

@@ -855,7 +855,7 @@ secugen_frame_chunk_cb (FpiUsbTransfer *transfer,
 
   /* Outside emulation a complete sensor frame is expected. */
   if (self->bulk_offset < SECUGEN_RAW_SIZE &&
-      g_strcmp0 (g_getenv ("FP_DEVICE_EMULATION"), "1") != 0)
+      fpi_device_emulation_mode_enabled (dev))
     {
       fp_warn ("Short image data: got %" G_GSIZE_FORMAT ", expected %d",
                self->bulk_offset, SECUGEN_RAW_SIZE);
@@ -2225,7 +2225,7 @@ dev_change_state (FpImageDevice      *dev,
        * starts with the finger already present, so report it directly -
        * the same approach other drivers use for replay-incompatible
        * hardware behavior (e.g. elanspi's HID reset skip). */
-      if (g_strcmp0 (g_getenv ("FP_DEVICE_EMULATION"), "1") == 0)
+      if (fpi_device_emulation_mode_enabled (FP_DEVICE (self)))
         {
           fpi_image_device_report_finger_status (dev, TRUE);
           break;

libfprint/drivers/synaptics/synaptics.c

@@ -1211,7 +1211,7 @@ prob_msg_cb (FpiDeviceSynaptics *self,
       return;
     }
 
-  if (g_strcmp0 (g_getenv ("FP_DEVICE_EMULATION"), "1") == 0)
+  if (fpi_device_emulation_mode_enabled (FP_DEVICE (self)))
     serial = g_strdup ("emulated-device");
   else
     serial = g_usb_device_get_string_descriptor (usb_dev,

libfprint/drivers/uru4000.c

@@ -1380,7 +1380,7 @@ dev_init (FpImageDevice *dev)
 
   g_clear_pointer (&self->rand, g_rand_free);
   self->rand = g_rand_new ();
-  if (g_strcmp0 (g_getenv ("FP_DEVICE_EMULATION"), "1") == 0)
+  if (fpi_device_emulation_mode_enabled (FP_DEVICE (dev)))
     g_rand_set_seed (self->rand, 0xFACADE);
 
   driver_data = fpi_device_get_driver_data (FP_DEVICE (dev));

libfprint/drivers/vfs0050.c

@@ -119,7 +119,7 @@ async_abort_callback (FpiUsbTransfer *transfer, FpDevice *device,
 
   /* In normal case endpoint is empty */
   if (g_error_matches (error, G_USB_DEVICE_ERROR, G_USB_DEVICE_ERROR_TIMED_OUT) ||
-      (g_strcmp0 (g_getenv ("FP_DEVICE_EMULATION"), "1") == 0 && transfer->actual_length == 0))
+      (fpi_device_emulation_mode_enabled (device) && transfer->actual_length == 0))
     {
       g_clear_error (&error);
       fpi_ssm_next_state (transfer->ssm);

libfprint/fpi-device.c

@@ -50,6 +50,35 @@ fp_device_get_instance_private (FpDevice *self)
                             g_type_class_get_instance_private_offset (dev_class));
 }
 
+/**
+ * fpi_device_emulation_mode_enabled:
+ * @device: The #FpDevice to check
+ *
+ * Checks if the device is running in emulation mode, which is enabled by
+ * setting the FP_DEVICE_EMULATION environment variable to a '1' value.
+ * This is used by some drivers to enable special behavior for testing
+ * and development purposes.
+ */
+gboolean
+  (fpi_device_emulation_mode_enabled) (FpDevice *device)
+{
+  static gsize emulation_mode = 0;
+
+  /* FIXME: Add some build constraints to make sure this cannot ever be enabled
+   * in production, outside in the installed tests case.
+   */
+
+  /* This is a global value for now, but ideally we may support a different
+   * value per device.
+   */
+  if (g_once_init_enter (&emulation_mode))
+    g_once_init_leave (&emulation_mode,
+                       g_strcmp0 (g_getenv ("FP_DEVICE_EMULATION"), "1") == 0 ?
+                       TRUE : G_MAXSIZE);
+
+  return emulation_mode == TRUE;
+}
+
 /**
  * fpi_device_class_auto_initialize_features:
  * @device_class: An #FpDeviceClass to initialize

libfprint/fpi-device.h

@@ -332,4 +332,11 @@ gboolean fpi_device_report_finger_status_changes (FpDevice           *device,
                                                   FpFingerStatusFlags added_status,
                                                   FpFingerStatusFlags removed_status);
 
+/* Debugging utilities */
+
+#define fpi_device_emulation_mode_enabled(dev) \
+  G_UNLIKELY ((fpi_device_emulation_mode_enabled) ((dev)))
+
+gboolean (fpi_device_emulation_mode_enabled) (FpDevice *device);
+
 G_END_DECLS

libfprint/fpi-print.c

@@ -295,7 +295,7 @@ fpi_print_generate_user_id (FpPrint *print)
   if (!username)
     username = "nobody";
 
-  if (g_strcmp0 (g_getenv ("FP_DEVICE_EMULATION"), "1") == 0)
+  if (fpi_device_emulation_mode_enabled (NULL))
     rand_id = 0;
   else
     rand_id = g_random_int ();