Subject: Re: [BUG -next] ./usr/include/cxl/features.h:11:10: fatal error: uuid/uuid.h: No such file or directory

From: Dan Williams <[email-masked]>
Date: Mon, 31 Mar 2025 09:54:55 -0700

Jason Gunthorpe wrote:
> On Fri, Mar 28, 2025 at 05:26:42PM -0700, Dave Jiang wrote:
> > > For now the following builds for me, but it is a quite a mess to undo
> > > the assumption that that the hardware object definitions can not use
> > > uuid_t:
> > 
> > +Jason.
> 
> Seems invasive?

Yeah, it left a bad taste for me as well.

> Maybe just like below?

I like that this avoids converting to the kernel's uuid API, however,
not quite happy that it forces userspace to contend with the
type-conflict with uuid/uuid.h.

So how about one more riff on your idea?

-- 8< --
>From 6fbca9bb3e29f3a205861b9489a8fba46506e107 Mon Sep 17 00:00:00 2001
From: Dan Williams <[email-masked]>
Date: Mon, 31 Mar 2025 09:43:48 -0700
Subject: [PATCH] fwctl/cxl: Fix uuid_t usage in uapi
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The uuid_t type is kernel internal, and Paul reports the following build
error when it is used in a uapi header:

    usr/include/cxl/features.h:59:9: error: unknown type name ‘uuid_t’

Create a uuid type (__uapi_uuid_t) compatible with the longstanding
definition uuid/uuid.h for userspace builds, and use uuid_t directly for
kernel builds.

Suggested-by: Jason Gunthorpe <[email-masked]>
Reported-by: "Paul E. McKenney" <[email-masked]>
Closes: http://lore.kernel.org/f6489337-67c7-48c8-b48a-58603ec15328@paulmck-laptop
Fixes: 9b8e73cdb141 ("cxl: Move cxl feature command structs to user header")
Signed-off-by: Dan Williams <[email-masked]>
---
 include/uapi/cxl/features.h | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/include/uapi/cxl/features.h b/include/uapi/cxl/features.h
index d6db8984889f..dd8874860cec 100644
--- a/include/uapi/cxl/features.h
+++ b/include/uapi/cxl/features.h
@@ -8,10 +8,14 @@
 #define _UAPI_CXL_FEATURES_H_
 
 #include <linux/types.h>
-#ifndef __KERNEL__
-#include <uuid/uuid.h>
-#else
+
+typedef unsigned char __uapi_uuid_t[16];
+
+#ifdef __KERNEL__
 #include <linux/uuid.h>
+static_assert(sizeof(__uapi_uuid_t) == sizeof(uuid_t) &&
+	      __alignof__(__uapi_uuid_t) == __alignof__(uuid_t));
+#define __uapi_uuid_t uuid_t
 #endif
 
 /*
@@ -60,7 +64,7 @@ struct cxl_mbox_get_sup_feats_in {
  * Get Supported Features Supported Feature Entry
  */
 struct cxl_feat_entry {
-	uuid_t uuid;
+	__uapi_uuid_t uuid;
 	__le16 id;
 	__le16 get_feat_size;
 	__le16 set_feat_size;
@@ -110,7 +114,7 @@ struct cxl_mbox_get_sup_feats_out {
  * CXL spec r3.2 section 8.2.9.6.2 Table 8-99
  */
 struct cxl_mbox_get_feat_in {
-	uuid_t uuid;
+	__uapi_uuid_t uuid;
 	__le16 offset;
 	__le16 count;
 	__u8 selection;
@@ -143,7 +147,7 @@ enum cxl_get_feat_selection {
  */
 struct cxl_mbox_set_feat_in {
 	__struct_group(cxl_mbox_set_feat_hdr, hdr, /* no attrs */,
-		uuid_t uuid;
+		__uapi_uuid_t uuid;
 		__le32 flags;
 		__le16 offset;
 		__u8 version;
-- 
2.48.1