From: Ben Hutchings <ben@decadent.org.uk>
Subject: x86/efi: Autoload efivars
Date: Mon, 18 Mar 2013 22:59:14 +0000
Bug-Debian: http://bugs.debian.org/703363
Forwarded: no

efivars is generally useful to have on EFI systems, and in some cases
it may be impossible to load it after a kernel upgrade in order to
complete a boot loader update.  efi-pstore is similarly useful though
less critical.  At the same time we don't want to waste memory on
non-EFI systems by making them built-in.

Instead, give them module aliases as if they are platform drivers, and
register a corresponding platform device whenever EFI runtime services
are available.  This should trigger udev to load them.

---
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -42,6 +42,7 @@
 #include <linux/io.h>
 #include <linux/reboot.h>
 #include <linux/bcd.h>
+#include <linux/platform_device.h>
 
 #include <asm/setup.h>
 #include <asm/efi.h>
@@ -783,6 +784,20 @@ void __init efi_late_init(void)
 	efi_bgrt_init();
 }
 
+#ifdef CONFIG_EFI_VARS_MODULE
+static int __init efi_load_efivars(void)
+{
+	struct platform_device *pdev;
+
+	if (!efi_enabled(EFI_RUNTIME_SERVICES))
+		return 0;
+
+	pdev = platform_device_register_simple("efivars", 0, NULL, 0);
+	return IS_ERR(pdev) ? PTR_ERR(pdev) : 0;
+}
+device_initcall(efi_load_efivars);
+#endif
+
 void __init efi_set_executable(efi_memory_desc_t *md, bool executable)
 {
 	u64 addr, npages;
--- a/drivers/firmware/efi/efivars.c
+++ b/drivers/firmware/efi/efivars.c
@@ -77,6 +77,7 @@ MODULE_AUTHOR("Matt Domsch <Matt_Domsch@
 MODULE_DESCRIPTION("sysfs interface to EFI Variables");
 MODULE_LICENSE("GPL");
 MODULE_VERSION(EFIVARS_VERSION);
+MODULE_ALIAS("platform:efivars");
 
 LIST_HEAD(efivar_sysfs_list);
 EXPORT_SYMBOL_GPL(efivar_sysfs_list);
--- a/drivers/firmware/efi/efi-pstore.c
+++ b/drivers/firmware/efi/efi-pstore.c
@@ -250,3 +250,4 @@ module_exit(efivars_pstore_exit);
 
 MODULE_DESCRIPTION("EFI variable backend for pstore");
 MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:efivars");