[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>

1 files changed, 42 insertions, 0 deletions

diff --git a/lib/iomap_copy.c b/lib/iomap_copy.c
new file mode 100644
index 000000000000..a6b1e271d53c
--- /dev/null
+++ b/lib/iomap_copy.c
@@ -0,0 +1,42 @@
+/*
+ * 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);