linux/drivers/firmware/efi/dev-path-parser.c

// SPDX-License-Identifier: GPL-2.0
/*
 * dev-path-parser.c - EFI Device Path parser
 * Copyright (C) 2016 Lukas Wunner <[email protected]>
 *
 * 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/acpi.h>
#include <linux/efi.h>
#include <linux/pci.h>

static long __init parse_acpi_path(const struct efi_dev_path *node,
				   struct device *parent, struct device **child)
{ … }

static int __init match_pci_dev(struct device *dev, void *data)
{ … }

static long __init parse_pci_path(const struct efi_dev_path *node,
				  struct device *parent, struct device **child)
{ … }

/*
 * Insert parsers for further node types here.
 *
 * Each parser takes a pointer to the @node and to the @parent (will be NULL
 * for the first device path node). If a device corresponding to @node was
 * found below @parent, its reference count should be incremented and the
 * device returned in @child.
 *
 * The return value should be 0 on success or a negative int on failure.
 * The special return values 0x01 (EFI_DEV_END_INSTANCE) and 0xFF
 * (EFI_DEV_END_ENTIRE) signal the end of the device path, only
 * parse_end_path() is supposed to return this.
 *
 * Be sure to validate the node length and contents before commencing the
 * search for a device.
 */

static long __init parse_end_path(const struct efi_dev_path *node,
				  struct device *parent, struct device **child)
{ … }

/**
 * efi_get_device_by_path - find device by EFI Device Path
 * @node: EFI Device Path
 * @len: maximum length of EFI Device Path in bytes
 *
 * Parse a series of EFI Device Path nodes at @node and find the corresponding
 * device.  If the device was found, its reference count is incremented and a
 * pointer to it is returned.  The caller needs to drop the reference with
 * put_device() after use.  The @node pointer is updated to point to the
 * location immediately after the "End of Hardware Device Path" node.
 *
 * If another Device Path instance follows, @len is decremented by the number
 * of bytes consumed.  Otherwise @len is set to %0.
 *
 * If a Device Path node is malformed or its corresponding device is not found,
 * @node is updated to point to this offending node and an ERR_PTR is returned.
 *
 * If @len is initially %0, the function returns %NULL.  Thus, to iterate over
 * all instances in a path, the following idiom may be used:
 *
 *	while (!IS_ERR_OR_NULL(dev = efi_get_device_by_path(&node, &len))) {
 *		// do something with dev
 *		put_device(dev);
 *	}
 *	if (IS_ERR(dev))
 *		// report error
 *
 * Devices can only be found if they're already instantiated. Most buses
 * instantiate devices in the "subsys" initcall level, hence the earliest
 * initcall level in which this function should be called is "fs".
 *
 * Returns the device on success or
 *	%ERR_PTR(-ENODEV) if no device was found,
 *	%ERR_PTR(-EINVAL) if a node is malformed or exceeds @len,
 *	%ERR_PTR(-ENOTSUPP) if support for a node type is not yet implemented.
 */
struct device * __init efi_get_device_by_path(const struct efi_dev_path **node,
					      size_t *len)
{ … }