efivars: Expose efivars functionality to external drivers.

Signed-off-by: Mike Waychison <mikew@google.com>
Cc: Matt Domsch <Matt_Domsch@dell.com>,
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 37 insertions, 0 deletions

diff --git a/include/linux/efi.h b/include/linux/efi.h
index fb737bc19a8c..33fa1203024e 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -397,4 +397,41 @@ static inline void memrange_efi_to_native(u64 *addr, u64 *npages)
         *addr &= PAGE_MASK;
 }
 
+#if defined(CONFIG_EFI_VARS) || defined(CONFIG_EFI_VARS_MODULE)
+/*
+ * EFI Variable support.
+ *
+ * Different firmware drivers can expose their EFI-like variables using
+ * the following.
+ */
+
+struct efivar_operations {
+        efi_get_variable_t *get_variable;
+        efi_get_next_variable_t *get_next_variable;
+        efi_set_variable_t *set_variable;
+};
+
+struct efivars {
+        /*
+         * ->lock protects two things:
+         * 1) ->list - adds, removals, reads, writes
+         * 2) ops.[gs]et_variable() calls.
+         * It must not be held when creating sysfs entries or calling kmalloc.
+         * ops.get_next_variable() is only called from register_efivars(),
+         * which is protected by the BKL, so that path is safe.
+         */
+        spinlock_t lock;
+        struct list_head list;
+        struct kset *kset;
+        struct bin_attribute *new_var, *del_var;
+        const struct efivar_operations *ops;
+};
+
+int register_efivars(struct efivars *efivars,
+                     const struct efivar_operations *ops,
+                     struct kobject *parent_kobj);
+void unregister_efivars(struct efivars *efivars);
+
+#endif /* CONFIG_EFI_VARS */
+
 #endif /* _LINUX_EFI_H */