4 files changed, 229 insertions, 0 deletions

diff --git a/drivers/firmware/efi/Kconfig b/drivers/firmware/efi/Kconfig
index c981be17d3c0..893fda48fcdd 100644
--- a/drivers/firmware/efi/Kconfig
+++ b/drivers/firmware/efi/Kconfig
@@ -133,3 +133,8 @@ endmenu
 
 config UEFI_CPER
 	bool
+
+config EFI_DEV_PATH_PARSER
+	bool
+	depends on ACPI
+	default n
diff --git a/drivers/firmware/efi/Makefile b/drivers/firmware/efi/Makefile
index c8a439f6d715..3e91ae31f9d1 100644
--- a/drivers/firmware/efi/Makefile
+++ b/drivers/firmware/efi/Makefile
@@ -21,6 +21,7 @@ obj-$(CONFIG_EFI_STUB)			+= libstub/
 obj-$(CONFIG_EFI_FAKE_MEMMAP)		+= fake_mem.o
 obj-$(CONFIG_EFI_BOOTLOADER_CONTROL)	+= efibc.o
 obj-$(CONFIG_EFI_TEST)			+= test/
+obj-$(CONFIG_EFI_DEV_PATH_PARSER)	+= dev-path-parser.o
 
 arm-obj-$(CONFIG_EFI)			:= arm-init.o arm-runtime.o
 obj-$(CONFIG_ARM)			+= $(arm-obj-y)
diff --git a/drivers/firmware/efi/dev-path-parser.c b/drivers/firmware/efi/dev-path-parser.c
new file mode 100644
index 000000000000..85d1834ee9b7
--- /dev/null
+++ b/drivers/firmware/efi/dev-path-parser.c
@@ -0,0 +1,203 @@
+/*
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#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;
+}
diff --git a/include/linux/efi.h b/include/linux/efi.h
index f5a821d9b90c..261767212c47 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -1148,6 +1148,26 @@ struct efi_generic_dev_path {
 	u16 length;
 } __attribute ((packed));
 
+struct efi_dev_path {
+	u8 type;	/* can be replaced with unnamed */
+	u8 sub_type;	/* struct efi_generic_dev_path; */
+	u16 length;	/* once we've moved to -std=c11 */
+	union {
+		struct {
+			u32 hid;
+			u32 uid;
+		} acpi;
+		struct {
+			u8 fn;
+			u8 dev;
+		} pci;
+	};
+} __attribute ((packed));
+
+#if IS_ENABLED(CONFIG_EFI_DEV_PATH_PARSER)
+struct device *efi_get_device_by_path(struct efi_dev_path **node, size_t *len);
+#endif
+
 static inline void memrange_efi_to_native(u64 *addr, u64 *npages)
 {
 	*npages = PFN_UP(*addr + (*npages<<EFI_PAGE_SHIFT)) - PFN_DOWN(*addr);