[PATCH v4 05/10] selftests: Add additional kernel functions to tools/include/

These are needed by the VFIO mlx5 selftest in the following patches,
which includes some headers from mlx5 and also needs a few more
MMIO-related features.

- DECLARE_FLEX_ARRAY in new tools/include/linux/stddef.h (wraps
  existing __DECLARE_FLEX_ARRAY from uapi/linux/stddef.h)

- dma_wmb/dma_rmb barriers: x86 uses compiler barrier
  (DMA-coherent), arm64 uses dmb oshst/oshld (outer-shareable for
  device visibility), generic fallback uses wmb/rmb

- ioread32be/iowrite32be in tools/include/asm-generic/io.h for
  big-endian MMIO register access

Assisted-by: Claude:claude-opus-4.6
Reviewed-by: David Matlack <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>
---
 tools/arch/arm64/include/asm/barrier.h |  4 ++++
 tools/arch/x86/include/asm/barrier.h   |  5 +++++
 tools/include/asm-generic/io.h         | 28 ++++++++++++++++++++++++++
 tools/include/asm/barrier.h            |  8 ++++++++
 tools/include/linux/stddef.h           | 10 +++++++++
 5 files changed, 55 insertions(+)
 create mode 100644 tools/include/linux/stddef.h

diff --git a/tools/arch/arm64/include/asm/barrier.h b/tools/arch/arm64/include/asm/barrier.h
index 3b9b41331c4f16..abdc64fc3c70f0 100644
--- a/tools/arch/arm64/include/asm/barrier.h
+++ b/tools/arch/arm64/include/asm/barrier.h
@@ -24,6 +24,10 @@
 #define smp_wmb()	asm volatile("dmb ishst" ::: "memory")
 #define smp_rmb()	asm volatile("dmb ishld" ::: "memory")
 
+/* DMA barriers use outer-shareable (osh) for device visibility */
+#define dma_rmb()	asm volatile("dmb oshld" ::: "memory")
+#define dma_wmb()	asm volatile("dmb oshst" ::: "memory")
+
 #define smp_store_release(p, v)						\
 do {									\
 	union { typeof(*p) __val; char __c[1]; } __u =			\
diff --git a/tools/arch/x86/include/asm/barrier.h b/tools/arch/x86/include/asm/barrier.h
index 0adf295dd5b6aa..0b51431fa530ea 100644
--- a/tools/arch/x86/include/asm/barrier.h
+++ b/tools/arch/x86/include/asm/barrier.h
@@ -43,4 +43,9 @@ do {						\
 	___p1;					\
 })
 #endif /* defined(__x86_64__) */
+
+/* x86 is DMA-coherent so DMA barriers are just compiler barriers */
+#define dma_rmb()	barrier()
+#define dma_wmb()	barrier()
+
 #endif /* _TOOLS_LINUX_ASM_X86_BARRIER_H */
diff --git a/tools/include/asm-generic/io.h b/tools/include/asm-generic/io.h
index e5a0b07ad452a6..0d89decdafb818 100644
--- a/tools/include/asm-generic/io.h
+++ b/tools/include/asm-generic/io.h
@@ -479,4 +479,32 @@ static inline void writesq(volatile void __iomem *addr, const void *buffer,
 }
 #endif
 
+/*
+ * ioread/iowrite for big-endian MMIO registers.
+ */
+
+#ifndef ioread32be
+#define ioread32be ioread32be
+static inline u32 ioread32be(const volatile void __iomem *addr)
+{
+	return bswap_32(readl(addr));
+}
+#endif
+
+#ifndef iowrite32be
+#define iowrite32be iowrite32be
+static inline void iowrite32be(u32 value, volatile void __iomem *addr)
+{
+	writel(bswap_32(value), addr);
+}
+#endif
+
+#ifndef iowrite64be
+#define iowrite64be iowrite64be
+static inline void iowrite64be(u64 value, volatile void __iomem *addr)
+{
+	writeq(bswap_64(value), addr);
+}
+#endif
+
 #endif /* _TOOLS_ASM_GENERIC_IO_H */
diff --git a/tools/include/asm/barrier.h b/tools/include/asm/barrier.h
index 0c21678ac5e65f..e7e0c7de5a2ffe 100644
--- a/tools/include/asm/barrier.h
+++ b/tools/include/asm/barrier.h
@@ -47,6 +47,14 @@
 # define smp_mb()	mb()
 #endif
 
+#ifndef dma_rmb
+# define dma_rmb()	rmb()
+#endif
+
+#ifndef dma_wmb
+# define dma_wmb()	wmb()
+#endif
+
 #ifndef smp_store_release
 # define smp_store_release(p, v)		\
 do {						\
diff --git a/tools/include/linux/stddef.h b/tools/include/linux/stddef.h
new file mode 100644
index 00000000000000..99182ea4a1419b
--- /dev/null
+++ b/tools/include/linux/stddef.h
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _TOOLS_LINUX_STDDEF_H
+#define _TOOLS_LINUX_STDDEF_H
+
+#include_next <linux/stddef.h>
+
+#define DECLARE_FLEX_ARRAY(TYPE, NAME) \
+	__DECLARE_FLEX_ARRAY(TYPE, NAME)
+
+#endif /* _TOOLS_LINUX_STDDEF_H */
-- 
2.43.0