Hi, Masahiro Yamada writes: > drivers/usb/gadget/legacy/Kconfig creates a 'choice' inside another > 'choice'. > > The outer choice: line 17 "USB Gadget precomposed configurations" > The inner choice: line 484 "EHCI Debug Device mode" > > I wondered why the whole legacy gadget drivers reside in such a big > choice block. > > This dates back to 2003, "[PATCH] USB: fix for multiple definition of > `usb_gadget_get_string'". [1] > > At that time, the global function, usb_gadget_get_string(), was linked > into multiple drivers. That was why only one driver was able to become > built-in at the same time. > > Later, commit a84d9e5361bc ("usb: gadget: start with libcomposite") > moved usb_gadget_get_string() to a separate module, libcomposite.ko > instead of including usbstring.c from multiple modules. > > More and more refactoring was done, and after commit 1bcce939478f > ("usb: gadget: multi: convert to new interface of f_mass_storage"), > you can link multiple gadget drivers into vmlinux without causing > multiple definition error. > > This is the only user of the nested choice structure ever. Removing > this mess will make some Kconfig cleanups possible. > > [1]: https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/?id=fee4cf49a81381e072c063571d1aadbb29207408 > > Signed-off-by: Masahiro Yamada Greg, if you want to pick this for v5.7, please go ahead: Acked-by: Felipe Balbi -- balbi