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Commit eeee7853 authored by Paul Mundt's avatar Paul Mundt
Browse files

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: default avatarPaul Mundt <lethal@linux-sh.org>
parent 8dafc346

Documentation/kernel-parameters.txt

+2 −0
Original line number Diff line number Diff line
@@ -1544,6 +1544,8 @@ and is between 256 and 4096 characters. It is defined in the file 
			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.

arch/sh/kernel/io_trapped.c

+13 −0
Original line number Diff line number Diff line
@@ -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 @@ EXPORT_SYMBOL_GPL(trapped_mem); 
#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 @@ int register_trapped_io(struct trapped_io *tiop) 
	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;