On Mon, Jan 25, 2021 at 12:40 PM Krzysztof Kozlowski <krzk@xxxxxxxxxx> wrote: > On Mon, 25 Jan 2021 at 12:36, Arnd Bergmann <arnd@xxxxxxxxxx> wrote: > > > > From: Arnd Bergmann <arnd@xxxxxxxx> > > > > When CONFIG_ATH9K is built-in but LED support is in a loadable > > module, both ath9k drivers fails to link: > > > > x86_64-linux-ld: drivers/net/wireless/ath/ath9k/gpio.o: in function `ath_deinit_leds': > > gpio.c:(.text+0x36): undefined reference to `led_classdev_unregister' > > x86_64-linux-ld: drivers/net/wireless/ath/ath9k/gpio.o: in function `ath_init_leds': > > gpio.c:(.text+0x179): undefined reference to `led_classdev_register_ext' > > > > The problem is that the 'imply' keyword does not enforce any dependency > > but is only a weak hint to Kconfig to enable another symbol from a > > defconfig file. > > > > Change imply to a 'depends on LEDS_CLASS' that prevents the incorrect > > configuration but still allows building the driver without LED support. > > > > The 'select MAC80211_LEDS' is now ensures that the LED support is > > actually used if it is present, and the added Kconfig dependency > > on MAC80211_LEDS ensures that it cannot be enabled manually when it > > has no effect. > > But we do not want to have this dependency (selecting MAC80211_LEDS). > I fixed this problem here: > https://lore.kernel.org/lkml/20201227143034.1134829-1-krzk@xxxxxxxxxx/ > Maybe let's take this approach? Generally speaking, I don't like to have a device driver specific Kconfig setting 'select' a subsystem', for two reasons: - you suddenly get asked for tons of new LED specific options when enabling seemingly benign options - Mixing 'depends on' and 'select' leads to bugs with circular dependencies that usually require turning some other 'select' into 'depends on'. The problem with LEDS_CLASS in particular is that there is a mix of drivers using one vs the other roughly 50:50. Arnd
