1 files changed, 71 insertions, 0 deletions
diff --git a/arch/xtensa/include/uapi/asm/swab.h b/arch/xtensa/include/uapi/asm/swab.h
new file mode 100644
index 000000000..e677cf4cc
--- /dev/null
+++ b/arch/xtensa/include/uapi/asm/swab.h
@@ -0,0 +1,71 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * include/asm-xtensa/swab.h
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2001 - 2005 Tensilica Inc.
+ */
+
+#ifndef _XTENSA_SWAB_H
+#define _XTENSA_SWAB_H
+
+#include <linux/types.h>
+#include <linux/compiler.h>
+
+#define __SWAB_64_THRU_32__
+
+static inline __attribute_const__ __u32 __arch_swab32(__u32 x)
+{
+    __u32 res;
+    /* instruction sequence from Xtensa ISA release 2/2000 */
+    __asm__("ssai     8           \n\t"
+	    "srli     %0, %1, 16  \n\t"
+	    "src      %0, %0, %1  \n\t"
+	    "src      %0, %0, %0  \n\t"
+	    "src      %0, %1, %0  \n"
+	    : "=&a" (res)
+	    : "a" (x)
+	    );
+    return res;
+}
+#define __arch_swab32 __arch_swab32
+
+static inline __attribute_const__ __u16 __arch_swab16(__u16 x)
+{
+    /* Given that 'short' values are signed (i.e., can be negative),
+     * we cannot assume that the upper 16-bits of the register are
+     * zero.  We are careful to mask values after shifting.
+     */
+
+    /* There exists an anomaly between xt-gcc and xt-xcc.  xt-gcc
+     * inserts an extui instruction after putting this function inline
+     * to ensure that it uses only the least-significant 16 bits of
+     * the result.  xt-xcc doesn't use an extui, but assumes the
+     * __asm__ macro follows convention that the upper 16 bits of an
+     * 'unsigned short' result are still zero.  This macro doesn't
+     * follow convention; indeed, it leaves garbage in the upport 16
+     * bits of the register.
+
+     * Declaring the temporary variables 'res' and 'tmp' to be 32-bit
+     * types while the return type of the function is a 16-bit type
+     * forces both compilers to insert exactly one extui instruction
+     * (or equivalent) to mask off the upper 16 bits. */
+
+    __u32 res;
+    __u32 tmp;
+
+    __asm__("extui    %1, %2, 8, 8\n\t"
+	    "slli     %0, %2, 8   \n\t"
+	    "or       %0, %0, %1  \n"
+	    : "=&a" (res), "=&a" (tmp)
+	    : "a" (x)
+	    );
+
+    return res;
+}
+#define __arch_swab16 __arch_swab16
+
+#endif /* _XTENSA_SWAB_H */