atags_parse.c

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/*
 * Tag parsing.
 *
 * Copyright (C) 1995-2001 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

/*
 * This is the traditional way of passing data to the kernel at boot time.  Rather
 * than passing a fixed inflexible structure to the kernel, we pass a list
 * of variable-sized tags to the kernel.  The first tag must be a ATAG_CORE
 * tag for the list to be recognised (to distinguish the tagged list from
 * a param_struct).  The list is terminated with a zero-length tag (this tag
 * is not parsed in any way).
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/root_dev.h>
#include <linux/screen_info.h>

#include <asm/setup.h>
#include <asm/system_info.h>
#include <asm/page.h>
#include <asm/mach/arch.h>

#include "atags.h"

static char default_command_line[COMMAND_LINE_SIZE] __initdata = CONFIG_CMDLINE;

#ifndef MEM_SIZE
#define MEM_SIZE    (16*1024*1024)
#endif

static struct {
    struct tag_header hdr1;
    struct tag_core   core;
    struct tag_header hdr2;
    struct tag_mem32  mem;
    struct tag_header hdr3;
} default_tags __initdata = {
    { tag_size(tag_core), ATAG_CORE },
    { 1, PAGE_SIZE, 0xff },
    { tag_size(tag_mem32), ATAG_MEM },
    { MEM_SIZE },
    { 0, ATAG_NONE }
};

static int __init parse_tag_core(const struct tag *tag)
{
    if (tag->hdr.size > 2) {
        if ((tag->u.core.flags & 1) == 0)
            root_mountflags &= ~MS_RDONLY;
        ROOT_DEV = old_decode_dev(tag->u.core.rootdev);
    }
    return 0;
}

__tagtable(ATAG_CORE, parse_tag_core);

static int __init parse_tag_mem32(const struct tag *tag)
{
    return arm_add_memory(tag->u.mem.start, tag->u.mem.size);
}

__tagtable(ATAG_MEM, parse_tag_mem32);

#if defined(CONFIG_VGA_CONSOLE) || defined(CONFIG_DUMMY_CONSOLE)
static int __init parse_tag_videotext(const struct tag *tag)
{
    screen_info.orig_x            = tag->u.videotext.x;
    screen_info.orig_y            = tag->u.videotext.y;
    screen_info.orig_video_page   = tag->u.videotext.video_page;
    screen_info.orig_video_mode   = tag->u.videotext.video_mode;
    screen_info.orig_video_cols   = tag->u.videotext.video_cols;
    screen_info.orig_video_ega_bx = tag->u.videotext.video_ega_bx;
    screen_info.orig_video_lines  = tag->u.videotext.video_lines;
    screen_info.orig_video_isVGA  = tag->u.videotext.video_isvga;
    screen_info.orig_video_points = tag->u.videotext.video_points;
    return 0;
}

__tagtable(ATAG_VIDEOTEXT, parse_tag_videotext);
#endif

#ifdef CONFIG_BLK_DEV_RAM
static int __init parse_tag_ramdisk(const struct tag *tag)
{
    extern int rd_size, rd_image_start, rd_prompt, rd_doload;

    rd_image_start = tag->u.ramdisk.start;
    rd_doload = (tag->u.ramdisk.flags & 1) == 0;
    rd_prompt = (tag->u.ramdisk.flags & 2) == 0;

    if (tag->u.ramdisk.size)
        rd_size = tag->u.ramdisk.size;

    return 0;
}

__tagtable(ATAG_RAMDISK, parse_tag_ramdisk);
#endif

static int __init parse_tag_serialnr(const struct tag *tag)
{
    system_serial_low = tag->u.serialnr.low;
    system_serial_high = tag->u.serialnr.high;
    return 0;
}

__tagtable(ATAG_SERIAL, parse_tag_serialnr);

static int __init parse_tag_revision(const struct tag *tag)
{
    system_rev = tag->u.revision.rev;
    return 0;
}

__tagtable(ATAG_REVISION, parse_tag_revision);

static int __init parse_tag_cmdline(const struct tag *tag)
{
#if defined(CONFIG_CMDLINE_EXTEND)
    strlcat(default_command_line, " ", COMMAND_LINE_SIZE);
    strlcat(default_command_line, tag->u.cmdline.cmdline,
        COMMAND_LINE_SIZE);
#elif defined(CONFIG_CMDLINE_FORCE)
    pr_warning("Ignoring tag cmdline (using the default kernel command line)\n");
#else
    strlcpy(default_command_line, tag->u.cmdline.cmdline,
        COMMAND_LINE_SIZE);
#endif
    return 0;
}

__tagtable(ATAG_CMDLINE, parse_tag_cmdline);

/*
 * Scan the tag table for this tag, and call its parse function.
 * The tag table is built by the linker from all the __tagtable
 * declarations.
 */
static int __init parse_tag(const struct tag *tag)
{
    extern struct tagtable __tagtable_begin, __tagtable_end;
    struct tagtable *t;

    for (t = &__tagtable_begin; t < &__tagtable_end; t++)
        if (tag->hdr.tag == t->tag) {
            t->parse(tag);
            break;
        }

    return t < &__tagtable_end;
}

/*
 * Parse all tags in the list, checking both the global and architecture
 * specific tag tables.
 */
static void __init parse_tags(const struct tag *t)
{
    for (; t->hdr.size; t = tag_next(t))
        if (!parse_tag(t))
            printk(KERN_WARNING
                "Ignoring unrecognised tag 0x%08x\n",
                t->hdr.tag);
}

static void __init squash_mem_tags(struct tag *tag)
{
    for (; tag->hdr.size; tag = tag_next(tag))
        if (tag->hdr.tag == ATAG_MEM)
            tag->hdr.tag = ATAG_NONE;
}

struct machine_desc * __init setup_machine_tags(phys_addr_t __atags_pointer,
                        unsigned int machine_nr)
{
    struct tag *tags = (struct tag *)&default_tags;
    struct machine_desc *mdesc = NULL, *p;
    char *from = default_command_line;

    default_tags.mem.start = PHYS_OFFSET;

    /*
     * locate machine in the list of supported machines.
     */
    for_each_machine_desc(p)
        if (machine_nr == p->nr) {
            printk("Machine: %s\n", p->name);
            mdesc = p;
            break;
        }

    if (!mdesc) {
        early_print("\nError: unrecognized/unsupported machine ID"
                " (r1 = 0x%08x).\n\n", machine_nr);
        dump_machine_table(); /* does not return */
    }

    if (__atags_pointer)
        tags = phys_to_virt(__atags_pointer);
    else if (mdesc->atag_offset)
        tags = (void *)(PAGE_OFFSET + mdesc->atag_offset);

#if defined(CONFIG_DEPRECATED_PARAM_STRUCT)
    /*
     * If we have the old style parameters, convert them to
     * a tag list.
     */
    if (tags->hdr.tag != ATAG_CORE)
        convert_to_tag_list(tags);
#endif
    if (tags->hdr.tag != ATAG_CORE) {
        early_print("Warning: Neither atags nor dtb found\n");
        tags = (struct tag *)&default_tags;
    }

    if (mdesc->fixup)
        mdesc->fixup(tags, &from, &meminfo);

    if (tags->hdr.tag == ATAG_CORE) {
        if (meminfo.nr_banks != 0)
            squash_mem_tags(tags);
        save_atags(tags);
        parse_tags(tags);
    }

    /* parse_early_param needs a boot_command_line */
    strlcpy(boot_command_line, from, COMMAND_LINE_SIZE);

    return mdesc;
}