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[217.226.152.150]) by smtp.gmail.com with ESMTPSA id r2sm8981284wma.26.2019.06.10.04.45.32 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 10 Jun 2019 04:45:32 -0700 (PDT) Received: from localhost.daheim ([127.0.0.1] helo=debian64.localnet) by debian64.daheim with esmtp (Exim 4.92) (envelope-from ) id 1haIjz-0003hl-Kc; Mon, 10 Jun 2019 13:45:31 +0200 From: Christian Lamparter To: Kalle Valo Cc: linux-wireless@vger.kernel.org Subject: Re: [PATCH] carl9170: fix enum compare splat Date: Mon, 10 Jun 2019 13:45:31 +0200 Message-ID: <1601416.I41mb68Wgz@debian64> In-Reply-To: <87pnnlncll.fsf@codeaurora.org> References: <20190608144947.744-1-chunkeey@gmail.com> <87pnnlncll.fsf@codeaurora.org> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="UTF-8" Sender: linux-wireless-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org On Monday, June 10, 2019 9:06:30 AM CEST Kalle Valo wrote: > Christian Lamparter writes: >=20 > > This patch fixes a noisy warning triggered by -Wenum-compare > > > > |main.c:1390:31: warning: comparison between =E2=80=98enum nl80211_ac= =E2=80=99 > > | and =E2=80=98enum ar9170_txq=E2=80=99 [-Wenum-compare] > > | BUILD_BUG_ON(NL80211_NUM_ACS > __AR9170_NUM_TXQ); > > | ^ > > | [...] > > > > This is a little bit unfortunate, since the number of queues > > (hence NL80211_NUM_ACS) is a constant based on the IEEE 802.11 > > (much like IEEE80211_NUM_ACS) and __AR9170_NUM_TXQ is more or > > less defined by the AR9170 hardware. >=20 > Is the warning enabled by default? TBH I'm not seeing how useful this > warning is for kernel development. It is included in the "-Wall" (which is coming from "KBUILD_CFLAGS"=20 in the main Makefile). I tried debian's gcc starting from 4.6 to the lastest 8.3. They all complain about it in various degrees. https://gcc.gnu.org/onlinedocs/gcc-4.6.0/gcc/Warning-Options.html#Warning-O= ptions > > --- a/drivers/net/wireless/ath/carl9170/main.c > > +++ b/drivers/net/wireless/ath/carl9170/main.c > > @@ -1387,7 +1387,7 @@ static int carl9170_op_conf_tx(struct ieee80211_h= w *hw, > > int ret; > > =20 > > BUILD_BUG_ON(ARRAY_SIZE(ar9170_qmap) !=3D __AR9170_NUM_TXQ); > > - BUILD_BUG_ON(NL80211_NUM_ACS > __AR9170_NUM_TXQ); > > + BUILD_BUG_ON((size_t)NL80211_NUM_ACS > (size_t)__AR9170_NUM_TXQ); >=20 > IMHO this just makes the code worse. Does it make sense to workaround > (stupid) compiler warnings like this? True. What's worse: This isn't really code. The BUILD_BUG_ON Macro is there to guard but it's getting compiled away. I could also just drop it.