Undefined symbol failures if CONFIG_USB=m

[srcshelton]

Describe the bug

If CONFIG_USB_DWCOTG=y is set but CONFIG_USB=m, building the 6.1.73/stable_20240124 (and likely previous) kernel(s) fails with:

  LD      .tmp_vmlinux.kallsyms1
ld.lld: error: undefined symbol: usb_hcd_check_unlink_urb
>>> referenced by xarray.c
>>>               vmlinux.o:(_complete)
>>> referenced by xarray.c
>>>               vmlinux.o:(dwc_otg_urb_dequeue)

ld.lld: error: undefined symbol: usb_hcd_unlink_urb_from_ep
>>> referenced by xarray.c
>>>               vmlinux.o:(_complete)
>>> referenced by xarray.c
>>>               vmlinux.o:(_complete)
>>> referenced by xarray.c
>>>               vmlinux.o:(dwc_otg_urb_enqueue)
>>> referenced 1 more times

ld.lld: error: undefined symbol: usb_hcd_giveback_urb
>>> referenced by xarray.c
>>>               vmlinux.o:(_complete)
>>> referenced by xarray.c
>>>               vmlinux.o:(completion_tasklet_func)
>>> referenced by xarray.c
>>>               vmlinux.o:(dwc_otg_urb_dequeue)

ld.lld: error: undefined symbol: usb_create_hcd
>>> referenced by xarray.c
>>>               vmlinux.o:(hcd_init)

ld.lld: error: undefined symbol: usb_put_hcd
>>> referenced by xarray.c
>>>               vmlinux.o:(hcd_init)
>>> referenced by xarray.c
>>>               vmlinux.o:(hcd_remove)

ld.lld: error: undefined symbol: usb_add_hcd
>>> referenced by xarray.c
>>>               vmlinux.o:(hcd_init)

ld.lld: error: undefined symbol: usb_remove_hcd
>>> referenced by xarray.c
>>>               vmlinux.o:(hcd_remove)

ld.lld: error: undefined symbol: usb_hcd_resume_root_hub
>>> referenced by xarray.c
>>>               vmlinux.o:(hcd_start)
>>> referenced by xarray.c
>>>               vmlinux.o:(_start)

ld.lld: error: undefined symbol: usb_hcd_link_urb_to_ep
>>> referenced by xarray.c
>>>               vmlinux.o:(dwc_otg_urb_enqueue)
make[3]: *** [/usr/src/linux-6.1.73-raspberrypi/scripts/Makefile.vmlinux:34: vmlinux] Error 1
make[2]: *** [/usr/src/linux-6.1.73-raspberrypi/Makefile:1255: vmlinux] Error 2
make[1]: *** [/usr/src/linux-6.1.73-raspberrypi/Makefile:369: __build_one_by_one] Error 2
make: *** [Makefile:238: __sub-make] Error 2

Steps to reproduce the behaviour

cd linux ; make USB_DWCOTG=y USB=m clean vmlinux

Device (s)

Raspberry Pi CM4

System

Kernel 6.1.73

Logs

No response

Additional context

The easy fix would be to make CONFIG_USB_DWCOTG depend on CONFIG_USB=y, but might it be possible to fix the DWC driver code to be able to be built as a module itself, or integrated in such a way that it works if USB support overall is a module?

[srcshelton]

Similarly, with 6.6.20/ 6f16847 (untagged but matching https://github.com/raspberrypi/firmware/tree/1.20240306), CONFIG_FB_BCM2708 requires CONFIG_FB_DEVICE (for dev in struct fb_info), despite the Help text for CONFIG_FB_DEVICE reading:

Say Y here if you want the legacy /dev/fb* device file and interfaces within sysfs anc [sic] procfs. It is only required if you have userspace programs that depend on fbdev for graphics output.
This does not affect the framebuffer console.
If unsure, say N.

[pelwell]

Why are you singling out 6.1 for the USB_DWCOTG dependency problem? For me, the 6.6 kernel is the same.

[pelwell]

See #6112. Note that this fixes the rpi-6.6.y tree. rpi-6.1.y is not being developed on, but these patches could be back-ported as being low risk.

[srcshelton]

Why are you singling out 6.1 for the USB_DWCOTG dependency problem? For me, the 6.6 kernel is the same.

I've not tested USB_DWCOTG on 6.6 myself, but I'm not meaning to infer the the issue is specific to 6.1.

(When I first filed the bug, I was trying to build a 6.1 kernel. The 6.6 kernel sources still aren't tagged by the looks of things (see #6063), but I've moved on to using them regardless.)