The pci-epf-ntb driver uses configfs APIs, so it should depend on CONFIGFS_FS to prevent build errors. ld: drivers/pci/endpoint/functions/pci-epf-ntb.o: in function `epf_ntb_add_cfs': pci-epf-ntb.c:(.text+0x1b): undefined reference to `config_group_init_type_name' Fixes: 7dc64244f9e9 ("PCI: endpoint: Add EP function driver to provide NTB functionality") Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> Cc: Kishon Vijay Abraham I <kishon@xxxxxx> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> Cc: linux-pci@xxxxxxxxxxxxxxx --- You may switch to 'select CONFIG_FS_FS' if you feel strongly about it. drivers/pci/endpoint/functions/Kconfig | 1 + 1 file changed, 1 insertion(+) --- linux-next-20210202.orig/drivers/pci/endpoint/functions/Kconfig +++ linux-next-20210202/drivers/pci/endpoint/functions/Kconfig @@ -16,6 +16,7 @@ config PCI_EPF_TEST config PCI_EPF_NTB tristate "PCI Endpoint NTB driver" depends on PCI_ENDPOINT + depends on CONFIGFS_FS help Select this configuration option to enable the NTB driver for PCI Endpoint. NTB driver implements NTB controller