efi/dev-path-parser: Add struct definition for vendor type device path nodes

In preparation of adding support for loading the initrd via a special
device path, add the struct definition of a vendor GUIDed device path
node to efi.h.

Since we will be producing these data structures rather than just
consumsing the ones instantiated by the firmware, refactor the various
device path node definitions so we can take the size of each node using
sizeof() rather than having to resort to opaque arithmetic in the static
initializers.

While at it, drop the #if IS_ENABLED() check for the declaration of
efi_get_device_by_path(), which is unnecessary, and constify its first
argument as well.

Signed-off-by: Ard Biesheuvel <[e-mail]>

drivers/firmware/efi/apple-properties.c

···
 };
 
 static void __init unmarshal_key_value_pairs(struct dev_header *dev_header,
-					     struct device *dev, void *ptr,
+					     struct device *dev, const void *ptr,
 					     struct property_entry entry[])
 {
 	int i;
···
 	while (offset + sizeof(struct dev_header) < properties->len) {
 		struct dev_header *dev_header = (void *)properties + offset;
 		struct property_entry *entry = NULL;
+		const struct efi_dev_path *ptr;
 		struct device *dev;
 		size_t len;
 		int ret, i;
-		void *ptr;
 
 		if (offset + dev_header->len > properties->len ||
 		    dev_header->len <= sizeof(*dev_header)) {
···
 		ptr = dev_header->path;
 		len = dev_header->len - sizeof(*dev_header);
 
-		dev = efi_get_device_by_path((struct efi_dev_path **)&ptr, &len);
+		dev = efi_get_device_by_path(&ptr, &len);
 		if (IS_ERR(dev)) {
 			pr_err("device path parse error %ld at %#zx:\n",
-			       PTR_ERR(dev), ptr - (void *)dev_header);
+			       PTR_ERR(dev), (void *)ptr - (void *)dev_header);
 			print_hex_dump(KERN_ERR, pr_fmt(), DUMP_PREFIX_OFFSET,
 			       16, 1, dev_header, dev_header->len, true);
 			dev = NULL;

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

···
 		return !strcmp("0", hid_uid.uid);
 }
 
-static long __init parse_acpi_path(struct efi_dev_path *node,
+static long __init parse_acpi_path(const 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)
+	if (node->header.length != 12)
 		return -EINVAL;
 
 	sprintf(hid_uid.hid[0].id, "%c%c%c%04X",
···
 	return dev_is_pci(dev) && to_pci_dev(dev)->devfn == devfn;
 }
 
-static long __init parse_pci_path(struct efi_dev_path *node,
+static long __init parse_pci_path(const struct efi_dev_path *node,
 				  struct device *parent, struct device **child)
 {
 	unsigned int devfn;
 
-	if (node->length != 6)
+	if (node->header.length != 6)
 		return -EINVAL;
 	if (!parent)
 		return -EINVAL;
···
  * search for a device.
  */
 
-static long __init parse_end_path(struct efi_dev_path *node,
+static long __init parse_end_path(const struct efi_dev_path *node,
 				  struct device *parent, struct device **child)
 {
-	if (node->length != 4)
+	if (node->header.length != 4)
 		return -EINVAL;
-	if (node->sub_type != EFI_DEV_END_INSTANCE &&
-	    node->sub_type != EFI_DEV_END_ENTIRE)
+	if (node->header.sub_type != EFI_DEV_END_INSTANCE &&
+	    node->header.sub_type != EFI_DEV_END_ENTIRE)
 		return -EINVAL;
 	if (!parent)
 		return -ENODEV;
 
 	*child = get_device(parent);
-	return node->sub_type;
+	return node->header.sub_type;
 }
 
 /**
···
  *	%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,
+struct device * __init efi_get_device_by_path(const struct efi_dev_path **node,
 					      size_t *len)
 {
 	struct device *parent = NULL, *child;
···
 		return NULL;
 
 	while (!ret) {
-		if (*len < 4 || *len < (*node)->length)
+		if (*len < 4 || *len < (*node)->header.length)
 			ret = -EINVAL;
-		else if ((*node)->type     == EFI_DEV_ACPI &&
-			 (*node)->sub_type == EFI_DEV_BASIC_ACPI)
+		else if ((*node)->header.type		== EFI_DEV_ACPI &&
+			 (*node)->header.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)
+		else if ((*node)->header.type		== EFI_DEV_HW &&
+			 (*node)->header.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))
+		else if (((*node)->header.type		== EFI_DEV_END_PATH ||
+			  (*node)->header.type		== EFI_DEV_END_PATH2))
 			ret = parse_end_path(*node, parent, &child);
 		else
 			ret = -ENOTSUPP;
···
 			return ERR_PTR(ret);
 
 		parent = child;
-		*node  = (void *)*node + (*node)->length;
-		*len  -= (*node)->length;
+		*node  = (void *)*node + (*node)->header.length;
+		*len  -= (*node)->header.length;
 	}
 
 	if (ret == EFI_DEV_END_ENTIRE)

include/linux/efi.h

···
 #define   EFI_DEV_END_ENTIRE			0xFF
 
 struct efi_generic_dev_path {
-	u8 type;
-	u8 sub_type;
-	u16 length;
-} __attribute ((packed));
+	u8				type;
+	u8				sub_type;
+	u16				length;
+} __packed;
+
+struct efi_acpi_dev_path {
+	struct efi_generic_dev_path	header;
+	u32				hid;
+	u32				uid;
+} __packed;
+
+struct efi_pci_dev_path {
+	struct efi_generic_dev_path	header;
+	u8				fn;
+	u8				dev;
+} __packed;
+
+struct efi_vendor_dev_path {
+	struct efi_generic_dev_path	header;
+	efi_guid_t			vendorguid;
+	u8				vendordata[];
+} __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;
+		struct efi_generic_dev_path	header;
+		struct efi_acpi_dev_path	acpi;
+		struct efi_pci_dev_path		pci;
+		struct efi_vendor_dev_path	vendor;
 	};
-} __attribute ((packed));
+} __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
+struct device *efi_get_device_by_path(const struct efi_dev_path **node,
+				      size_t *len);
 
 static inline void memrange_efi_to_native(u64 *addr, u64 *npages)
 {