[tip:efi/urgent] efi: Add comment to avoid future expanding of sysfs systab

[tip-bot for Dave Young]

Commit-ID:  0b02e448a2ebb46eb9be4f1bdfc87112bd420cbf
Gitweb:     https://git.kernel.org/tip/0b02e448a2ebb46eb9be4f1bdfc87112bd420cbf
Author:     Dave Young <dyoung@xxxxxxxxxx>
AuthorDate: Wed, 6 Dec 2017 09:50:10 +0000
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 6 Dec 2017 19:32:23 +0100

efi: Add comment to avoid future expanding of sysfs systab

/sys/firmware/efi/systab shows several different values, it breaks sysfs
one file one value design.  But since there are already userspace tools
depend on it eg. kexec-tools so add code comment to alert future expanding
of this file.

Signed-off-by: Dave Young <dyoung@xxxxxxxxxx>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-efi@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/20171206095010.24170-4-ard.biesheuvel@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 drivers/firmware/efi/efi.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index c3eefa1..557a478 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -109,6 +109,8 @@ struct kobject *efi_kobj;
 /*
  * Let's not leave out systab information that snuck into
  * the efivars driver
+ * Note, do not add more fields in systab sysfs file as it breaks sysfs
+ * one value per file rule!
  */
 static ssize_t systab_show(struct kobject *kobj,
 			   struct kobj_attribute *attr, char *buf)