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From:   Kalle Valo <kvalo@codeaurora.org>
To:     Christian Lamparter <chunkeey@gmail.com>
Cc:     linux-wireless@vger.kernel.org
Subject: Re: [PATCH] carl9170: fix enum compare splat
References: <20190608144947.744-1-chunkeey@gmail.com>
Date:   Mon, 10 Jun 2019 10:06:30 +0300
In-Reply-To: <20190608144947.744-1-chunkeey@gmail.com> (Christian Lamparter's
        message of "Sat, 8 Jun 2019 16:49:45 +0200")
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Christian Lamparter <chunkeey@gmail.com> writes:

> 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.

Is the warning enabled by default? TBH I'm not seeing how useful this
warning is for kernel development.

> --- 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_hw =
*hw,
>  	int ret;
>=20=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);

IMHO this just makes the code worse. Does it make sense to workaround
(stupid) compiler warnings like this?

--=20
Kalle Valo