edd: add default mode CONFIG_EDD_OFF=n, override with edd={on,off}

Add a kernel parameter option to 'edd' to enable/disable BIOS Enhanced Disk
Drive Services.  CONFIG_EDD_OFF disables EDD while still compiling EDD into
the kernel.  Default behavior can be forced using 'edd=on' or 'edd=off' as
a kernel parameter.

[akpm@linux-foundation.org: fix kernel-parameters.txt]
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Matt Domsch <Matt_Domsch@dell.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Randy.Dunlap" <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 1 deletions

diff --git a/arch/x86/boot/edd.c b/arch/x86/boot/edd.c
index d84a48ece785..03399d64013b 100644
--- a/arch/x86/boot/edd.c
+++ b/arch/x86/boot/edd.c
@@ -126,17 +126,25 @@ void query_edd(void)
 {
         char eddarg[8];
         int do_mbr = 1;
+#ifdef CONFIG_EDD_OFF
+        int do_edd = 0;
+#else
         int do_edd = 1;
+#endif
         int be_quiet;
         int devno;
         struct edd_info ei, *edp;
         u32 *mbrptr;
 
         if (cmdline_find_option("edd", eddarg, sizeof eddarg) > 0) {
-                if (!strcmp(eddarg, "skipmbr") || !strcmp(eddarg, "skip"))
+                if (!strcmp(eddarg, "skipmbr") || !strcmp(eddarg, "skip")) {
+                        do_edd = 1;
                         do_mbr = 0;
+                }
                 else if (!strcmp(eddarg, "off"))
                         do_edd = 0;
+                else if (!strcmp(eddarg, "on"))
+                        do_edd = 1;
         }
 
         be_quiet = cmdline_find_option_bool("quiet");