Move the default byteswap implementation into asm-generic so that it can
be included from arch code.

This is required by RISC-V in order to have a fallback implementation
without duplicating it.

Signed-off-by: Ignacio Encinas <ignacio@iencinas.com>
---
 include/uapi/asm-generic/swab.h | 32 ++++++++++++++++++++++++++++++++
 include/uapi/linux/swab.h       | 33 +--------------------------------
 2 files changed, 33 insertions(+), 32 deletions(-)

diff --git a/include/uapi/asm-generic/swab.h b/include/uapi/asm-generic/swab.h
index f2da4e4fd4d1..43d83df007a6 100644
--- a/include/uapi/asm-generic/swab.h
+++ b/include/uapi/asm-generic/swab.h
@@ -16,4 +16,36 @@
 #endif
 #endif
 
+/*
+ * casts are necessary for constants, because we never know how for sure
+ * how U/UL/ULL map to __u16, __u32, __u64. At least not in a portable way.
+ */
+#define ___constant_swab16(x) ((__u16)(				\
+	(((__u16)(x) & (__u16)0x00ffU) << 8) |			\
+	(((__u16)(x) & (__u16)0xff00U) >> 8)))
+
+#define ___constant_swab32(x) ((__u32)(				\
+	(((__u32)(x) & (__u32)0x000000ffUL) << 24) |		\
+	(((__u32)(x) & (__u32)0x0000ff00UL) <<  8) |		\
+	(((__u32)(x) & (__u32)0x00ff0000UL) >>  8) |		\
+	(((__u32)(x) & (__u32)0xff000000UL) >> 24)))
+
+#define ___constant_swab64(x) ((__u64)(				\
+	(((__u64)(x) & (__u64)0x00000000000000ffULL) << 56) |	\
+	(((__u64)(x) & (__u64)0x000000000000ff00ULL) << 40) |	\
+	(((__u64)(x) & (__u64)0x0000000000ff0000ULL) << 24) |	\
+	(((__u64)(x) & (__u64)0x00000000ff000000ULL) <<  8) |	\
+	(((__u64)(x) & (__u64)0x000000ff00000000ULL) >>  8) |	\
+	(((__u64)(x) & (__u64)0x0000ff0000000000ULL) >> 24) |	\
+	(((__u64)(x) & (__u64)0x00ff000000000000ULL) >> 40) |	\
+	(((__u64)(x) & (__u64)0xff00000000000000ULL) >> 56)))
+
+#define ___constant_swahw32(x) ((__u32)(			\
+	(((__u32)(x) & (__u32)0x0000ffffUL) << 16) |		\
+	(((__u32)(x) & (__u32)0xffff0000UL) >> 16)))
+
+#define ___constant_swahb32(x) ((__u32)(			\
+	(((__u32)(x) & (__u32)0x00ff00ffUL) << 8) |		\
+	(((__u32)(x) & (__u32)0xff00ff00UL) >> 8)))
+
 #endif /* _ASM_GENERIC_SWAB_H */
diff --git a/include/uapi/linux/swab.h b/include/uapi/linux/swab.h
index 01717181339e..ca808c492996 100644
--- a/include/uapi/linux/swab.h
+++ b/include/uapi/linux/swab.h
@@ -6,38 +6,7 @@
 #include <linux/stddef.h>
 #include <asm/bitsperlong.h>
 #include <asm/swab.h>
-
-/*
- * casts are necessary for constants, because we never know how for sure
- * how U/UL/ULL map to __u16, __u32, __u64. At least not in a portable way.
- */
-#define ___constant_swab16(x) ((__u16)(				\
-	(((__u16)(x) & (__u16)0x00ffU) << 8) |			\
-	(((__u16)(x) & (__u16)0xff00U) >> 8)))
-
-#define ___constant_swab32(x) ((__u32)(				\
-	(((__u32)(x) & (__u32)0x000000ffUL) << 24) |		\
-	(((__u32)(x) & (__u32)0x0000ff00UL) <<  8) |		\
-	(((__u32)(x) & (__u32)0x00ff0000UL) >>  8) |		\
-	(((__u32)(x) & (__u32)0xff000000UL) >> 24)))
-
-#define ___constant_swab64(x) ((__u64)(				\
-	(((__u64)(x) & (__u64)0x00000000000000ffULL) << 56) |	\
-	(((__u64)(x) & (__u64)0x000000000000ff00ULL) << 40) |	\
-	(((__u64)(x) & (__u64)0x0000000000ff0000ULL) << 24) |	\
-	(((__u64)(x) & (__u64)0x00000000ff000000ULL) <<  8) |	\
-	(((__u64)(x) & (__u64)0x000000ff00000000ULL) >>  8) |	\
-	(((__u64)(x) & (__u64)0x0000ff0000000000ULL) >> 24) |	\
-	(((__u64)(x) & (__u64)0x00ff000000000000ULL) >> 40) |	\
-	(((__u64)(x) & (__u64)0xff00000000000000ULL) >> 56)))
-
-#define ___constant_swahw32(x) ((__u32)(			\
-	(((__u32)(x) & (__u32)0x0000ffffUL) << 16) |		\
-	(((__u32)(x) & (__u32)0xffff0000UL) >> 16)))
-
-#define ___constant_swahb32(x) ((__u32)(			\
-	(((__u32)(x) & (__u32)0x00ff00ffUL) << 8) |		\
-	(((__u32)(x) & (__u32)0xff00ff00UL) >> 8)))
+#include <asm-generic/swab.h>
 
 /*
  * Implement the following as inlines, but define the interface using

-- 
2.49.0

Hi Ignacio,

kernel test robot noticed the following build warnings:

[auto build test WARNING on a7f2e10ecd8f18b83951b0bab47ddaf48f93bf47]

url:    https://github.com/intel-lab-lkp/linux/commits/Ignacio-Encinas/include-uapi-linux-swab-h-move-default-implementation-for-swab-macros-into-asm-generic/20250404-051744
base:   a7f2e10ecd8f18b83951b0bab47ddaf48f93bf47
patch link:    https://lore.kernel.org/r/20250403-riscv-swab-v3-1-3bf705d80e33%40iencinas.com
patch subject: [PATCH v3 1/2] include/uapi/linux/swab.h: move default implementation for swab macros into asm-generic
config: i386-buildonly-randconfig-004-20250404 (https://download.01.org/0day-ci/archive/20250404/202504042300.it9RcOSt-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250404/202504042300.it9RcOSt-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202504042300.it9RcOSt-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> usr/include/asm-generic/swab.h:21: found __[us]{8,16,32,64} type without #include <linux/types.h>

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki