From e4142f296b53bee16f47e2258d3767c798292fb6 Mon Sep 17 00:00:00 2001
From: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Date: Tue, 7 Oct 2025 18:13:44 +0200
Subject: [PATCH] include: linux: Add stddef.h

Import stddef.h from the Linux kernel sources v6.19-rc1 at revision
c2a756891bb4 ("uapi: wrap compiler_types.h in an ifdef instead of the
implicit strip")

The stddef.h header is imported to provide the __counted_by() symbol
which is not available in the header version shipped with, in example,
Debian 12.  __counted_by() will be used by the v4l2-isp.h header which
will be imported next.

Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
---
 include/linux/stddef.h         | 74 ++++++++++++++++++++++++++++++++++
 utils/update-kernel-headers.sh |  1 +
 2 files changed, 75 insertions(+)
 create mode 100644 include/linux/stddef.h

diff --git a/include/linux/stddef.h b/include/linux/stddef.h
new file mode 100644
index 00000000..48ee4438
--- /dev/null
+++ b/include/linux/stddef.h
@@ -0,0 +1,74 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _LINUX_STDDEF_H
+#define _LINUX_STDDEF_H
+
+
+#ifndef __always_inline
+#define __always_inline __inline__
+#endif
+
+/* Not all C++ standards support type declarations inside an anonymous union */
+#ifndef __cplusplus
+#define __struct_group_tag(TAG)		TAG
+#else
+#define __struct_group_tag(TAG)
+#endif
+
+/**
+ * __struct_group() - Create a mirrored named and anonyomous struct
+ *
+ * @TAG: The tag name for the named sub-struct (usually empty)
+ * @NAME: The identifier name of the mirrored sub-struct
+ * @ATTRS: Any struct attributes (usually empty)
+ * @MEMBERS: The member declarations for the mirrored structs
+ *
+ * Used to create an anonymous union of two structs with identical layout
+ * and size: one anonymous and one named. The former's members can be used
+ * normally without sub-struct naming, and the latter can be used to
+ * reason about the start, end, and size of the group of struct members.
+ * The named struct can also be explicitly tagged for layer reuse (C only),
+ * as well as both having struct attributes appended.
+ */
+#define __struct_group(TAG, NAME, ATTRS, MEMBERS...) \
+	union { \
+		struct { MEMBERS } ATTRS; \
+		struct __struct_group_tag(TAG) { MEMBERS } ATTRS NAME; \
+	} ATTRS
+
+#ifdef __cplusplus
+/* sizeof(struct{}) is 1 in C++, not 0, can't use C version of the macro. */
+#define __DECLARE_FLEX_ARRAY(T, member)	\
+	T member[0]
+#else
+/**
+ * __DECLARE_FLEX_ARRAY() - Declare a flexible array usable in a union
+ *
+ * @TYPE: The type of each flexible array element
+ * @NAME: The name of the flexible array member
+ *
+ * In order to have a flexible array member in a union or alone in a
+ * struct, it needs to be wrapped in an anonymous struct with at least 1
+ * named member, but that member can be empty.
+ */
+#define __DECLARE_FLEX_ARRAY(TYPE, NAME)	\
+	struct { \
+		struct { } __empty_ ## NAME; \
+		TYPE NAME[]; \
+	}
+#endif
+
+#ifndef __counted_by
+#define __counted_by(m)
+#endif
+
+#ifndef __counted_by_le
+#define __counted_by_le(m)
+#endif
+
+#ifndef __counted_by_be
+#define __counted_by_be(m)
+#endif
+
+#define __kernel_nonstring
+
+#endif /* _LINUX_STDDEF_H */
diff --git a/utils/update-kernel-headers.sh b/utils/update-kernel-headers.sh
index f298a2ae..3d402de2 100755
--- a/utils/update-kernel-headers.sh
+++ b/utils/update-kernel-headers.sh
@@ -53,6 +53,7 @@ headers="
 	linux/media-bus-format.h
 	linux/media.h
 	linux/rkisp1-config.h
+	linux/stddef.h
 	linux/udmabuf.h
 	linux/v4l2-common.h
 	linux/v4l2-controls.h