[PATCH v2 1/2] public/io: xs_wire: Document that EINVAL should always be first in xsd_errors

[Julien Grall <julien@xen.org>]

From: Julien Grall <jgrall@amazon.com>

Some tools (e.g. xenstored) always expect EINVAL to be first in xsd_errors.

Document it so, one doesn't add a new entry before hand by mistake.

Signed-off-by: Julien Grall <jgrall@amazon.com>

----

I have tried to add a BUILD_BUG_ON() but GCC complained that the value
was not a constant. I couldn't figure out a way to make GCC happy.

Changes in v2:
    - New patch
---
 xen/include/public/io/xs_wire.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/xen/include/public/io/xs_wire.h b/xen/include/public/io/xs_wire.h
index c1ec7c73e3b1..dd4c9c9b972d 100644
--- a/xen/include/public/io/xs_wire.h
+++ b/xen/include/public/io/xs_wire.h
@@ -76,6 +76,7 @@ static struct xsd_errors xsd_errors[]
 __attribute__((unused))
 #endif
     = {
+    /* /!\ Some users (e.g. xenstored) expect EINVAL to be the first entry. */
     XSD_ERROR(EINVAL),
     XSD_ERROR(EACCES),
     XSD_ERROR(EEXIST),
-- 
2.32.0