// SPDX-License-Identifier: GPL-2.0
/*
* dev-path-parser.c - EFI Device Path parser
* Copyright (C) 2016 Lukas Wunner <lukas@wunner.de>
*
* 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>
struct acpi_hid_uid {
struct acpi_device_id hid[2];
char uid[11]; /* UINT_MAX + null byte */
};
static int __init match_acpi_dev(struct device *dev, void *data)
{
struct acpi_hid_uid hid_uid = *(struct acpi_hid_uid *)data;
struct acpi_device *adev = to_acpi_device(dev);
if (acpi_match_device_ids(adev, hid_uid.hid))
return 0;
if (adev->pnp.unique_id)
return !strcmp(adev->pnp.unique_id, hid_uid.uid);
else
return !strcmp("0", hid_uid.uid);
}
static long __init parse_acpi_path(struct efi_dev_path *node,
struct device *parent, struct device **child)
{
struct acpi_hid_uid hid_uid = {};
struct device *phys_dev;
if (node->length != 12)
return -EINVAL;
sprintf(hid_uid.hid[0].id, "%c%c%c%04X",
'A' + ((node->acpi.hid >> 10) & 0x1f) - 1,
'A' + ((node->acpi.hid >> 5) & 0x1f) - 1,
'A' + ((node->acpi.hid >> 0) & 0x1f) - 1,
node->acpi.hid >> 16);
sprintf(hid_uid.uid, "%u", node->acpi.uid);
*child = bus_find_device(&acpi_bus_type, NULL, &hid_uid,
match_acpi_dev);
if (!*child)
return -ENODEV;
phys_dev = acpi_get_first_physical_node(to_acpi_device(*child));
if (phys_dev) {
get_device(phys_dev);
put_device(*child);
*child = phys_dev;
}
return 0;
}
static int __init match_pci_dev(struct device *dev, void *data)
{
unsigned int devfn = *(unsigned int *)data;
return dev_is_pci(dev) && to_pci_dev(dev)->devfn == devfn;
}
static long __init parse_pci_path(struct efi_dev_path *node,
struct device *parent, struct device **child)
{
unsigned int devfn;
if (node->length != 6)
return -EINVAL;
if (!parent)
return -EINVAL;
devfn = PCI_DEVFN(node->pci.dev, node->pci.fn);
*child = device_find_child(parent, &devfn, match_pci_dev);
if (!*child)
return -ENODEV;
return 0;
}
/*
* 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(struct efi_dev_path *node,
struct device *parent, struct device **child)
{
if (node->length != 4)
return -EINVAL;
if (node->sub_type != EFI_DEV_END_INSTANCE &&
node->sub_type != EFI_DEV_END_ENTIRE)
return -EINVAL;
if (!parent)
return -ENODEV;
*child = get_device(parent);
return node->sub_type;
}
/**
* 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(struct efi_dev_path **node,
size_t *len)
{
struct device *parent = NULL, *child;
long ret = 0;
if (!*len)
return NULL;
while (!ret) {
if (*len < 4 || *len < (*node)->length)
ret = -EINVAL;
else if ((*node)->type == EFI_DEV_ACPI &&
(*node)->sub_type == EFI_DEV_BASIC_ACPI)
ret = parse_acpi_path(*node, parent, &child);
else if ((*node)->type == EFI_DEV_HW &&
(*node)->sub_type == EFI_DEV_PCI)
ret = parse_pci_path(*node, parent, &child);
else if (((*node)->type == EFI_DEV_END_PATH ||
(*node)->type == EFI_DEV_END_PATH2))
ret = parse_end_path(*node, parent, &child);
else
ret = -ENOTSUPP;
put_device(parent);
if (ret < 0)
return ERR_PTR(ret);
parent = child;
*node = (void *)*node + (*node)->length;
*len -= (*node)->length;
}
if (ret == EFI_DEV_END_ENTIRE)
*len = 0;
return child;
}
