From: Arnd Bergmann <arnd@kernel.org>
To: Krzysztof Kozlowski <krzk@kernel.org>
Cc: QCA ath9k Development <ath9k-devel@qca.qualcomm.com>,
Kalle Valo <kvalo@codeaurora.org>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Johannes Berg <johannes@sipsolutions.net>,
Arnd Bergmann <arnd@arndb.de>,
Masahiro Yamada <masahiroy@kernel.org>,
Flavio Suligoi <f.suligoi@asem.it>,
linux-wireless <linux-wireless@vger.kernel.org>,
Networking <netdev@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] ath9k: fix build error with LEDS_CLASS=m
Date: Mon, 25 Jan 2021 14:08:42 +0100 [thread overview]
Message-ID: <CAK8P3a0apBUbck9Z3UMKfwSJw8a-UbbXLTLUvSyOKEwTgPLjqg@mail.gmail.com> (raw)
In-Reply-To: <CAJKOXPfteJ3Jia4Qd9DabjxcOtax3uDgi1fSbz4_+cHsJ1prQQ@mail.gmail.com>
On Mon, Jan 25, 2021 at 12:40 PM Krzysztof Kozlowski <krzk@kernel.org> wrote:
> On Mon, 25 Jan 2021 at 12:36, Arnd Bergmann <arnd@kernel.org> wrote:
> >
> > From: Arnd Bergmann <arnd@arndb.de>
> >
> > 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@kernel.org/
> 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
next prev parent reply other threads:[~2021-01-26 19:13 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-25 11:36 [PATCH] ath9k: fix build error with LEDS_CLASS=m Arnd Bergmann
2021-01-25 11:40 ` Krzysztof Kozlowski
2021-01-25 13:08 ` Arnd Bergmann [this message]
2021-01-25 13:27 ` Krzysztof Kozlowski
2021-01-25 14:38 ` Arnd Bergmann
2021-01-25 15:04 ` Krzysztof Kozlowski
2021-01-25 15:22 ` Arnd Bergmann
2021-01-27 10:35 ` Kalle Valo
2021-01-27 10:36 ` Johannes Berg
2021-01-28 7:30 ` Kalle Valo
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