path: root/scripts/dtc/libfdt/fdt_overlay.c

// SPDX-License-Identifier: (GPL-2.0-or-later OR BSD-2-Clause)
/*
 * libfdt - Flat Device Tree manipulation
 * Copyright (C) 2016 Free Electrons
 * Copyright (C) 2016 NextThing Co.
 */
#include "libfdt_env.h"

#include <fdt.h>
#include <libfdt.h>

#include "libfdt_internal.h"

/**
 * overlay_get_target_phandle - retrieves the target phandle of a fragment
 * @fdto: pointer to the device tree overlay blob
 * @fragment: node offset of the fragment in the overlay
 *
 * overlay_get_target_phandle() retrieves the target phandle of an
 * overlay fragment when that fragment uses a phandle (target
 * property) instead of a path (target-path property).
 *
 * returns:
 *      the phandle pointed by the target property
 *      0, if the phandle was not found
 *	-1, if the phandle was malformed
 */
static uint32_t overlay_get_target_phandle(const void *fdto, int fragment)
{
	const fdt32_t *val;
	int len;

	val = fdt_getprop(fdto, fragment, "target", &len);
	if (!val)
		return 0;

	if ((len != sizeof(*val)) || (fdt32_to_cpu(*val) == (uint32_t)-1))
		return (uint32_t)-1;

	return fdt32_to_cpu(*val);
}

int fdt_overlay_target_offset(const void *fdt, const void *fdto,
			      int fragment_offset, char const **pathp)
{
	uint32_t phandle;
	const char *path = NULL;
	int path_len = 0, ret;

	/* Try first to do a phandle based lookup */
	phandle = overlay_get_target_phandle(fdto, fragment_offset);
	if (phandle == (uint32_t)-1)
		return -FDT_ERR_BADPHANDLE;

	/* no phandle, try path */
	if (!phandle) {
		/* And then a path based lookup */
		path = fdt_getprop(fdto, fragment_offset, "target-path", &path_len);
		if (path)
			ret = fdt_path_offset(fdt, path);
		else
			ret = path_len;
	} else
		ret = fdt_node_offset_by_phandle(fdt, phandle);

	/*
	* If we haven't found either a target or a
	* target-path property in a node that contains a
	* __overlay__ subnode (we wouldn't be called
	* otherwise), consider it a improperly written
	* overlay
	*/
	if (ret < 0 && path_len == -FDT_ERR_NOTFOUND)
		ret = -FDT_ERR_BADOVERLAY;

	/* return on error */
	if (ret < 0)
		return ret;

	/* return pointer to path (if available) */
	if (pathp)
		*pathp = path ? path : NULL;

	return ret;
}

/**
 * overlay_phandle_add_offset - Increases a phandle by an offset
 * @fdt: Base device tree blob
 * @node: Device tree overlay blob
 * @name: Name of the property to modify (phandle or linux,phandle)
 * @delta: offset to apply
 *
 * overlay_phandle_add_offset() increments a node phandle by a given
 * offset.
 *
 * returns:
 *      0 on success.
 *      Negative error code on error
 */
static int overlay_phandle_add_offset(void *fdt, int node,
				      const char *name, uint32_t delta)
{
	fdt32_t *valp, val;
	int len;

	valp = fdt_getprop_w(fdt, node, name, &len);
	if (!valp)
		return len;

	if (len != sizeof(val))
		return -FDT_ERR_BADPHANDLE;

	val = fdt32_ld(valp);
	if (val + delta < val || val + delta == (uint32_t)-1)
		return -FDT_ERR_NOPHANDLES;

	fdt32_st(valp, val + delta);
	return 0;
}

/**
 * overlay_adjust_node_phandles - Offsets the phandles of a node
 * @fdto: Device tree overlay blob
 * @node: Offset of the node we want to adjust
 * @delta: Offset to shift the phandles of
 *
 * overlay_adjust_node_phandles() adds a constant to all the phandles
 * of a given node. This is mainly use as part of the overlay
 * application process, when we want to update all the overlay
 * phandles to not conflict with the overlays of the base device tree.
 *
 * returns:
 *      0 on success
 *      Negative error code on failure
 */
static int overlay_adjust_node_phandles(void *fdto, int node,
					uint32_t delta)
{
	int child;
	int ret;

	ret = overlay_phandle_add_offset(fdto, node, "phandle", delta);
	if (ret && ret != -FDT_ERR_NOTFOUND)
		return ret;

	ret = overlay_phandle_add_offset(fdto, node, "linux,phandle", delta);
	if (ret && ret != -FDT_ERR_NOTFOUND)
		return ret;

	fdt_for_each_subnode(child, fdto, node) {
		ret = overlay_adjust_node_phandles(fdto, child, delta);
		if (ret)
			return ret;
	}

	return 0;
}

/**
 * overlay_adjust_local_phandles - Adjust the phandles of a whole overlay
 * @fdto: Device tree overlay blob
 * @delta: Offset to shift the phandles of
 *
 * overlay_adjust_local_phandles() adds a constant to all the
 * phandles of an overlay. This is mainly use as part of the overlay
 * application process, when we want to update all the overlay
 * phandles to not conflict with the overlays of the base device tree.
 *
 * returns:
 *      0 on success
 *      Negative error code on failure
 */
static int overlay_adjust_local_phandles(void *fdto, uint32_t delta)
{
	/*
	 * Start adjusting the phandles from the overlay root
	 */
	return overlay_adjust_node_phandles(fdto, 0, delta);
}

/**
 * overlay_update_local_node_references - Adjust the overlay references
 * @fdto: Device tree overlay blob
 * @tree_node: Node offset of the node to operate on
 * @fixup_node: Node offset of the matching local fixups node
 * @delta: Offset to shift the phandles of
 *
 * overlay_update_local_nodes_references() update the phandles
 * pointing to a node within the device tree overlay by adding a
 * constant delta.
 *
 * This is mainly used as part of a device tree application process,
 * where you want the device tree overlays phandles to not conflict
 * with the ones from the base device tree before merging them.
 *
 * returns:
 *      0 on success
 *      Negative error code on failure
 */
static int overlay_update_local_node_references(void *fdto,
						int tree_node,
						int fixup_node,
						uint32_t delta)
{
	int fixup_prop;
	in