1. 根目录:
2. arch
3. mips
4. include
5. asm
6. fixmap.h

/*
 * fixmap.h: compile-time virtual memory allocation
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 1998 Ingo Molnar
 *
 * Support of BIGMEM added by Gerhard Wichert, Siemens AG, July 1999
 */

#ifndef _ASM_FIXMAP_H
#define _ASM_FIXMAP_H

#include <asm/page.h>
#include <spaces.h>
#ifdef CONFIG_HIGHMEM
#include <linux/threads.h>
#include <asm/kmap_types.h>
#endif

/*
 * Here we define all the compile-time 'special' virtual
 * addresses. The point is to have a constant address at
 * compile time, but to set the physical address only
 * in the boot process. We allocate these special  addresses
 * from the end of virtual memory (0xfffff000) backwards.
 * Also this lets us do fail-safe vmalloc(), we
 * can guarantee that these special addresses and
 * vmalloc()-ed addresses never overlap.
 *
 * these 'compile-time allocated' memory buffers are
 * fixed-size 4k pages. (or larger if used with an increment
 * highger than 1) use fixmap_set(idx,phys) to associate
 * physical memory with fixmap indices.
 *
 * TLB entries of such buffers will not be flushed across
 * task switches.
 */

/*
 * on UP currently we will have no trace of the fixmap mechanizm,
 * no page table allocations, etc. This might change in the
 * future, say framebuffers for the console driver(s) could be
 * fix-mapped?
 */
enum fixed_addresses {
#define FIX_N_COLOURS 8
	FIX_CMAP_BEGIN,
	FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * 2),
#ifdef CONFIG_HIGHMEM
	/* reserved pte's for temporary kernel mappings */
	FIX_KMAP_BEGIN = FIX_CMAP_END + 1,
	FIX_KMAP_END = FIX_KMAP_BEGIN+(KM_TYPE_NR*NR_CPUS)-1,
#endif
	__end_of_fixed_addresses
};

/*
 * used by vmalloc.c.
 *
 * Leave one empty page between vmalloc'ed areas and
 * the start of the fixmap, and leave one page empty
 * at the top of mem..
 */
#define FIXADDR_SIZE	(__end_of_fixed_addresses << PAGE_SHIFT)
#define FIXADDR_START	(FIXADDR_TOP - FIXADDR_SIZE)

#include <asm-generic/fixmap.h>

#define kmap_get_fixmap_pte(vaddr)					\
	pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr), (vaddr)), (vaddr)), (vaddr))

/*
 * Called from pgtable_init()
 */
extern void fixrange_init(unsigned long start, unsigned long end,
	pgd_t *pgd_base);


#endif