[RFC] [PATCH] Add memcpy32 function

["Bryan O'Sullivan" <bos@pathscale.com>]

In response to the comments that followed Roland Dreier posting our
InfiniPath driver for review last week, we've been making some cleanups
to our driver code.

As our chip requires 32-bit accesses, we need a copy function that
guarantees operating in such terms.  It was suggested that we make this
generic, with arch-specific optimised versions.

This patch introduces the generic copy routine, memcpy32.  At Andrew's
suggestion, I've put it in a new header file, include/linux/io.h, which
I've styled after include/linux/string.h.

Linus made some comments this morning about the manner in which the
functions in string.h are provided, but I wanted to float this patch for
review in any case, if only to see whether the alternative really is
preferred.

If desired, I can introduce instead an
include/asm-generic/memcpy32-algo.h header which defines the generic
memcpy32 routine, and edit all 20-odd asm-*/io.h files to use it.  That
seems wasteful, though.

Signed-off-by: Bryan O'Sullivan <bos@pathscale.com>

diff -r 0a6978881777 lib/Makefile
--- a/lib/Makefile	Fri Dec 23 01:41:03 2005 +0800
+++ b/lib/Makefile	Thu Dec 22 15:45:05 2005 -0800
@@ -5,7 +5,7 @@
 lib-y := errno.o ctype.o string.o vsprintf.o cmdline.o \
 	 bust_spinlocks.o rbtree.o radix-tree.o dump_stack.o \
 	 idr.o div64.o int_sqrt.o bitmap.o extable.o prio_tree.o \
-	 sha1.o
+	 sha1.o io.o
 
 lib-y	+= kobject.o kref.o kobject_uevent.o klist.o
 
diff -r 0a6978881777 include/linux/io.h
--- /dev/null	Thu Jan  1 00:00:00 1970 +0000
+++ b/include/linux/io.h	Thu Dec 22 15:45:05 2005 -0800
@@ -0,0 +1,32 @@
+#ifndef _LINUX_IO_H_
+#define _LINUX_IO_H_
+
+#include <linux/types.h>
+
+#ifdef __KERNEL__
+
+/*
+ * Include machine specific inline routines.
+ */
+#include <asm/io.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef __HAVE_ARCH_MEMCPY32
+/*
+ * Copy routine that is guaranteed to operate in terms of 32-bit
+ * quantities.  Source and dest must be 32-bit aligned.  Count is
+ * number of 32-bit quantities (NOT bytes) to copy.
+ */
+void *memcpy32(void *, const void *, __kernel_size_t);
+#endif
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __KERNEL__ */
+
+#endif /* _LINUX_IO_H_ */
diff -r 0a6978881777 lib/io.c
--- /dev/null	Thu Jan  1 00:00:00 1970 +0000
+++ b/lib/io.c	Thu Dec 22 15:45:05 2005 -0800
@@ -0,0 +1,21 @@
+#include <linux/io.h>
+
+#ifndef __HAVE_ARCH_MEMCPY32
+/**
+ * memcpy32 - Copy one area of memory to another, as a series of
+ * aligned 32-bit values.
+ * @dest: Where to copy to (must be 32-bit aligned)
+ * @src: Where to copy from (must be 32-bit aligned)
+ * @count: The number of 32-bit values to copy
+ */
+void *memcpy32(void *dest, const void *src, size_t count)
+{
+	u32 *tmp = dest;
+	u32 *s = src;
+
+	while (count--)
+		*tmp++ = *s++;
+	return dest;
+}
+EXPORT_SYMBOL_GPL(memcpy32);
+#endif