sh: Add a command line option for disabling I/O trapping.
This adds a 'noiotrap' kernel command line option to permit disabling of
I/O trapping. This is mostly useful for running on emulators where the
physical device limitations are not an issue.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 240257d..8b2067c 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1544,6 +1544,8 @@
Valid arguments: on, off
Default: on
+ noiotrap [SH] Disables trapped I/O port accesses.
+
noirqdebug [X86-32] Disables the code which attempts to detect and
disable unhandled interrupt sources.
diff --git a/arch/sh/kernel/io_trapped.c b/arch/sh/kernel/io_trapped.c
index 39cd7f3..c22853b 100644
--- a/arch/sh/kernel/io_trapped.c
+++ b/arch/sh/kernel/io_trapped.c
@@ -14,6 +14,7 @@
#include <linux/bitops.h>
#include <linux/vmalloc.h>
#include <linux/module.h>
+#include <linux/init.h>
#include <asm/system.h>
#include <asm/mmu_context.h>
#include <asm/uaccess.h>
@@ -32,6 +33,15 @@
#endif
static DEFINE_SPINLOCK(trapped_lock);
+static int trapped_io_disable __read_mostly;
+
+static int __init trapped_io_setup(char *__unused)
+{
+ trapped_io_disable = 1;
+ return 1;
+}
+__setup("noiotrap", trapped_io_setup);
+
int register_trapped_io(struct trapped_io *tiop)
{
struct resource *res;
@@ -39,6 +49,9 @@
struct page *pages[TRAPPED_PAGES_MAX];
int k, n;
+ if (unlikely(trapped_io_disable))
+ return 0;
+
/* structure must be page aligned */
if ((unsigned long)tiop & (PAGE_SIZE - 1))
goto bad;
