platform/x86: thinkpad_acpi: Get privacy-screen / lcdshadow ACPI handles only once

Get the privacy-screen / lcdshadow ACPI handles once and cache them,
instead of retrieving them every time we need them.

Reviewed-by: Emil Velikov <[e-mail]>
Reviewed-by: Lyude Paul <[e-mail]>
Reviewed-by: Mark Pearson <[e-mail]>
Signed-off-by: Hans de Goede <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/platform/x86/thinkpad_acpi.c

···
  * LCD Shadow subdriver, for the Lenovo PrivacyGuard feature
  */
 
+static acpi_handle lcdshadow_get_handle;
+static acpi_handle lcdshadow_set_handle;
 static int lcdshadow_state;
 
 static int lcdshadow_on_off(bool state)
 {
-	acpi_handle set_shadow_handle;
 	int output;
 
-	if (ACPI_FAILURE(acpi_get_handle(hkey_handle, "SSSS", &set_shadow_handle))) {
-		pr_warn("Thinkpad ACPI has no %s interface.\n", "SSSS");
-		return -EIO;
-	}
-
-	if (!acpi_evalf(set_shadow_handle, &output, NULL, "dd", (int)state))
+	if (!acpi_evalf(lcdshadow_set_handle, &output, NULL, "dd", (int)state))
 		return -EIO;
 
 	lcdshadow_state = state;
···
 
 static int tpacpi_lcdshadow_init(struct ibm_init_struct *iibm)
 {
-	acpi_handle get_shadow_handle;
+	acpi_status status1, status2;
 	int output;
 
-	if (ACPI_FAILURE(acpi_get_handle(hkey_handle, "GSSS", &get_shadow_handle))) {
+	status1 = acpi_get_handle(hkey_handle, "GSSS", &lcdshadow_get_handle);
+	status2 = acpi_get_handle(hkey_handle, "SSSS", &lcdshadow_set_handle);
+	if (ACPI_FAILURE(status1) || ACPI_FAILURE(status2)) {
 		lcdshadow_state = -ENODEV;
 		return 0;
 	}
 
-	if (!acpi_evalf(get_shadow_handle, &output, NULL, "dd", 0)) {
+	if (!acpi_evalf(lcdshadow_get_handle, &output, NULL, "dd", 0)) {
 		lcdshadow_state = -EIO;
 		return -EIO;
 	}