On Wed, Apr 24, 2019 at 6:05 PM Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > > On Fri, Apr 19, 2019 at 10:35 AM Greg Kroah-Hartman > <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > 2. Is there an easy way to figure out which config options enable > > > drivers reachable over USB? > > > > Looking for all options that depend on USB is a good start. > > > > > Right now our kernel config is based on one of the Debian kernel > > > configs, that supposedly enables enough relevant USB drivers. At the > > > same time it enables a lot of other unnecessary stuff, which makes the > > > kernel big and long to compile. Ideally, we would to have a way to > > > auto-generate a kernel config that enables all the relevant (enabled > > > by at least one of the distros) USB drivers. I've looked at whether > > > it's possible to figure out which particular options in some kernel > > > config are related to USB, but it seems that neither the option names, > > > nor the way they are grouped in the config file, are representative > > > enough. > > > > Yeah, it's hard to just carve out this type of configuration, but here's > > what I have done in the past to try to be sure I enabled all USB drivers > > in my kernel configuration. > > > > First, start with a "minimally working configuration" by running: > > make localmodconfig > > on a working system, with the needed modules for booting and operating > > properly already loaded. > > > > That gives you a .config file that should take only minutes to build, > > compared to much longer for the normal distro configuration (also be > > sure to disable some debugging options so you don't spend extra time > > building and stripping symbols). > > > > Boot and make sure that configuration works. > > > > Then, take that .config and do: > > - disable USB from the configuration by deleting the: > > CONFIG_USB_SUPPORT=y > > option from your .config > > - run 'make oldconfig' to disable all USB drivers > > - turn USB back on by setting CONFIG_USB_SUPPORT=y back on in > > your .config > > - run 'make oldconfig' and answer 'y' or 'm' to all of the > > driver options you are presented with. > > > > That usually catches almost all of them. Sometimes you need to make > > sure you have some other subsystem enabled (like SCSI), but odds are, if > > you start with a "normally stripped down" configuration that works, you > > should be fine. > > I suspect that make localmodconfig (+ switching CONFIG_USB_SUPPORT off > and on) would likely include a lot of stuff that we don't need (there > are many options that are =y, but not related to USB at all), but it > definitely sounds better than what I have right now (converting almost > all =m into =y). I'll give it a shot, thanks! I've tried this and unfortunately it doesn't work as desired. The reason is that localmodconfig will only enable options for the modules that are currently loaded, and if a module that some USB driver depends on is not loaded, then this driver won't be enabled after yes | make oldconfig. For example my machine didn't have the cfg80211 module loaded, and thus e.g. CONFIG_AT76C50X_USB didn't get enabled after oldconfig. However when I plug in a wireless USB adapter, cfg80211 gets loaded together with the USB driver for that adapter. I guess the same applies to other kinds of dependency modules (e.g. bluetooth). So this would only work if all the dependency modules are already loaded.
