on x86_64:
drivers/built-in.o: In function `b43_gpio_cleanup.isra.40':
main.c:(.text+0x1b425b): undefined reference to `bcma_chipco_gpio_control'
drivers/built-in.o: In function `b43_wireless_core_reset':
(.text+0x1b5fb6): undefined reference to `bcma_core_set_clockmode'
drivers/built-in.o: In function `b43_wireless_core_reset':
(.text+0x1b6058): undefined reference to `bcma_core_pll_ctl'
drivers/built-in.o: In function `b43_chip_init':
main.c:(.text+0x1b8444): undefined reference to `bcma_chipco_gpio_control'
drivers/built-in.o: In function `b43_wireless_core_init':
main.c:(.text+0x1b887b): undefined reference to `bcma_core_pci_irq_ctl'
drivers/built-in.o: In function `b43_bus_bcma_device_disable':
bus.c:(.text+0x1b9d46): undefined reference to `bcma_core_disable'
drivers/built-in.o: In function `b43_bus_bcma_device_enable':
bus.c:(.text+0x1b9d55): undefined reference to `bcma_core_enable'
drivers/built-in.o: In function `b43_bus_bcma_device_is_enabled':
bus.c:(.text+0x1b9d64): undefined reference to `bcma_core_is_enabled'
drivers/built-in.o: In function `b43_nphy_channel_setup':
phy_n.c:(.text+0x1c8fe5): undefined reference to `bcma_pmu_spuravoid_pllupdate'
drivers/built-in.o: In function `b43_phy_initn':
phy_n.c:(.text+0x1cb853): undefined reference to `bcma_chipco_gpio_control'
drivers/built-in.o: In function `b43_dma_init':
(.text+0x1d5790): undefined reference to `bcma_core_dma_translation'
drivers/built-in.o: In function `b43_init':
main.c:(.init.text+0xa07a): undefined reference to `__bcma_driver_register'
main.c:(.init.text+0xa09f): undefined reference to `bcma_driver_unregister'
drivers/built-in.o: In function `b43_exit':
main.c:(.exit.text+0x153a): undefined reference to `bcma_driver_unregister'
Probably mostly due to B43=y and BCMA=m.