DMI: add dmi_match

Add a wrapper for testing system_info which will handle also NULL
system infos.

This will be used by the ata PIIX driver.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Alexandru Romanescu <a_romanescu@yahoo.co.uk>
Cc: Tejun Heo <tj@kernel.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

include/linux/dmi.h

@@ -47,6 +47,7 @@ extern int dmi_name_in_vendors(const char *str);
 extern int dmi_name_in_serial(const char *str);
 extern int dmi_available;
 extern int dmi_walk(void (*decode)(const struct dmi_header *));
+extern bool dmi_match(enum dmi_field f, const char *str);
 
 #else
 
@@ -61,6 +62,8 @@ static inline int dmi_name_in_serial(const char *s) { return 0; }
 #define dmi_available 0
 static inline int dmi_walk(void (*decode)(const struct dmi_header *))
 	{ return -1; }
+static inline bool dmi_match(enum dmi_field f, const char *str)
+	{ return false; }
 
 #endif