drivers/of/fdt.c

/*
 * Functions for working with the Flattened Device Tree data format
 *
 * Copyright 2009 Benjamin Herrenschmidt, IBM Corp
 * benh@kernel.crashing.org
 *
 * 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.
 */

#include <linux/of.h>
#include <linux/of_fdt.h>

struct boot_param_header *initial_boot_params;

char *find_flat_dt_string(u32 offset)
{
	return ((char *)initial_boot_params) +
		initial_boot_params->off_dt_strings + offset;
}

/**
 * of_scan_flat_dt - scan flattened tree blob and call callback on each.
 * @it: callback function
 * @data: context data pointer
 *
 * This function is used to scan the flattened device-tree, it is
 * used to extract the memory information at boot before we can
 * unflatten the tree
 */
int __init of_scan_flat_dt(int (*it)(unsigned long node,
				     const char *uname, int depth,
				     void *data),
			   void *data)
{
	unsigned long p = ((unsigned long)initial_boot_params) +
		initial_boot_params->off_dt_struct;
	int rc = 0;
	int depth = -1;

	do {
		u32 tag = *((u32 *)p);
		char *pathp;

		p += 4;
		if (tag == OF_DT_END_NODE) {
			depth--;
			continue;
		}
		if (tag == OF_DT_NOP)
			continue;
		if (tag == OF_DT_END)
			break;
		if (tag == OF_DT_PROP) {
			u32 sz = *((u32 *)p);
			p += 8;
			if (initial_boot_params->version < 0x10)
				p = _ALIGN(p, sz >= 8 ? 8 : 4);
			p += sz;
			p = _ALIGN(p, 4);
			continue;
		}
		if (tag != OF_DT_BEGIN_NODE) {
			pr_err("Invalid tag %x in flat device tree!\n", tag);
			return -EINVAL;
		}
		depth++;
		pathp = (char *)p;
		p = _ALIGN(p + strlen(pathp) + 1, 4);
		if ((*pathp) == '/') {
			char *lp, *np;
			for (lp = NULL, np = pathp; *np; np++)
				if ((*np) == '/')
					lp = np+1;
			if (lp != NULL)
				pathp = lp;
		}
		rc = it(p, pathp, depth, data);
		if (rc != 0)
			break;
	} while (1);

	return rc;
}

/**
 * of_get_flat_dt_root - find the root node in the flat blob
 */
unsigned long __init of_get_flat_dt_root(void)
{
	unsigned long p = ((unsigned long)initial_boot_params) +
		initial_boot_params->off_dt_struct;

	while (*((u32 *)p) == OF_DT_NOP)
		p += 4;
	BUG_ON(*((u32 *)p) != OF_DT_BEGIN_NODE);
	p += 4;
	return _ALIGN(p + strlen((char *)p) + 1, 4);
}

/**
 * of_get_flat_dt_prop - Given a node in the flat blob, return the property ptr
 *
 * This function can be used within scan_flattened_dt callback to get
 * access to properties
 */
void *__init of_get_flat_dt_prop(unsigned long node, const char *name,
				 unsigned long *size)
{
	unsigned long p = node;

	do {
		u32 tag = *((u32 *)p);
		u32 sz, noff;
		const char *nstr;

		p += 4;
		if (tag == OF_DT_NOP)
			continue;
		if (tag != OF_DT_PROP)
			return NULL;

		sz = *((u32 *)p);
		noff = *((u32 *)(p + 4));
		p += 8;
		if (initial_boot_params->version < 0x10)
			p = _ALIGN(p, sz >= 8 ? 8 : 4);

		nstr = find_flat_dt_string(noff);
		if (nstr == NULL) {
			pr_warning("Can't find property index name !\n");
			return NULL;
		}
		if (strcmp(name, nstr) == 0) {
			if (size)
				*size = sz;
			return (void *)p;
		}
		p += sz;
		p = _ALIGN(p, 4);
	} while (1);
}