[PATCH] Introduce __iowrite32_copy

This arch-independent routine copies data to a memory-mapped I/O region,
using 32-bit accesses.  The naming is double-underscored to make it clear
that it does not guarantee write ordering, nor does it perform a memory
barrier afterwards; the kernel doc also explicitly states this.  This style
of access is required by some devices.

This change also introduces include/linux/io.h, at Andrew's suggestion.  It
only has one occupant at the moment, but is a logical destination for
oft-replicated contents of include/asm-*/{io,iomap}.h to migrate to.
Signed-off-by: Bryan O'Sullivan <bos@pathscale.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/io.h

+/*
+ * Copyright 2006 PathScale, Inc.  All Rights Reserved.
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#ifndef _LINUX_IO_H
+#define _LINUX_IO_H
+
+#include <asm/io.h>
+
+void __iowrite32_copy(void __iomem *to, const void *from, size_t count);
+
+#endif /* _LINUX_IO_H */

lib/Makefile

@@ -9,7 +9,7 @@ lib-y := errno.o ctype.o string.o vsprintf.o cmdline.o \
 
 lib-y	+= kobject.o kref.o kobject_uevent.o klist.o
 
-obj-y += sort.o parser.o halfmd4.o
+obj-y += sort.o parser.o halfmd4.o iomap_copy.o
 
 ifeq ($(CONFIG_DEBUG_KOBJECT),y)
 CFLAGS_kobject.o += -DDEBUG

lib/iomap_copy.c

+/*
+ * Copyright 2006 PathScale, Inc.  All Rights Reserved.
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include <linux/io.h>
+#include <linux/module.h>
+
+/**
+ * __iowrite32_copy - copy data to MMIO space, in 32-bit units
+ * @to: destination, in MMIO space (must be 32-bit aligned)
+ * @from: source (must be 32-bit aligned)
+ * @count: number of 32-bit quantities to copy
+ *
+ * Copy data from kernel space to MMIO space, in units of 32 bits at a
+ * time.  Order of access is not guaranteed, nor is a memory barrier
+ * performed afterwards.
+ */
+void __attribute__((weak)) __iowrite32_copy(void __iomem *to,
+					    const void *from,
+					    size_t count)
+{
+	u32 __iomem *dst = to;
+	const u32 *src = from;
+	const u32 *end = src + count;
+
+	while (src < end)
+		__raw_writel(*src++, dst++);
+}
+EXPORT_SYMBOL_GPL(__iowrite32_copy);