Re: [PATCH] carl9170: fix enum compare splat

[Kalle Valo <kvalo@codeaurora.org>]

Christian Lamparter <chunkeey@gmail.com> writes:

> On Tuesday, June 18, 2019 2:11:53 PM CEST Kalle Valo wrote:
>> Christian Lamparter <chunkeey@gmail.com> writes:
>> > On Monday, June 10, 2019 9:06:30 AM CEST Kalle Valo wrote:
>> >> Christian Lamparter <chunkeey@gmail.com> writes:
>> >> 
>> >> > This patch fixes a noisy warning triggered by -Wenum-compare
>> >> >
>> >> > |main.c:1390:31: warning: comparison between ‘enum nl80211_ac’
>> >> > |	and ‘enum ar9170_txq’ [-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.
>> >
>> > It is included in the "-Wall" (which is coming from "KBUILD_CFLAGS" 
>> > 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-Options
>> 
>> Ok, odd that I haven't noticed this warning. Maybe I have been just
>> blind.
>
> Sorry. No, I messed up there. I made a patch back in the day during the spectre
> mac80211 patches that I kept in my tree for the driver. But I now remember that
> I never published those because of that exact "warning".
> These lines are coming from there.
>  
>> >> > --- 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;
>> >> >  
>> >> >  	BUILD_BUG_ON(ARRAY_SIZE(ar9170_qmap) != __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?
>> >
>> > 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.
>> 
>> Either way is fine for me. If the GCC (by default) emits a warning for
>> this we need to silence that warning, so in that respect I guess we
>> should apply this. Unless better solutions come up, of course :)
>
> Note: I dropped this patch from patchwork. So, there's nothing that
> needs to be done now ;)

Thanks, except I would prefer that I drop the patch myself :) In
numerous cases I have been wondering there a patch has disappeared and
only after a while I realise the submitter deleted the patch altogether
(which also destroys the conversation from patchwork etc). IMHO that's
really bad UX in patchwork, I should file a bug report about that.

So in general it's enough to say "Kalle, please drop the patch" and I'll
do the rest.

> Well, except OT: Would you mind adding the QCA4019 boardfiles that
> have accumulated over the past six-ish months?

Yeah, those are in my queue. But I'll first want to implement a script
so that I don't need to manually add all of them and I just haven't
found the time for that.

-- 
Kalle Valo