Re: [PATCH] carl9170: fix enum compare splat

[Christian Lamparter <chunkeey@gmail.com>]

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 ;)

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

<https://www.mail-archive.com/ath10k@lists.infradead.org/msg09966.html>

That list already had:
ath10k-firmware: QCA4019 hw1.0: Add ASUS Lyra specific BDFs
ath10k-firmware: QCA4019 hw1.0: Add Linksys EA6350v3
ath10k-firmware: QCA4019 hw1.0: Add Qxwlan E2600AC specific BDFs
ath10k-firmware: QCA4019 hw1.0: Update OpenMesh A62 specific BDFs
ath10k-firmware: QCA9888 hw2.0: Update OpenMesh A62 specific BDFs
ath10k-firmware: QCA4019 hw1.0: Update OpenMesh A42 specific BDFs
ath10k-firmware: QCA4019 hw1.0: Add ALFA Network AP120C-AC specific BDF
ath10k-firmware: QCA4019 hw1.0: Add AVM FRITZ!Box 7530 specific BDFs
ath10k-firmware: QCA4019 hw1.0: Update Linksys EA6350v3 specific BDFs

and now there's even more:

+ ath10k-firmware: QCA4019 hw1.0: Add Qxwlan E2600AC specific BDFs
 (Watch out, there are multiple versions! The first ones are dodgy
 with a bad crc) 
 This should be the right "one"
 <https://www.mail-archive.com/ath10k@lists.infradead.org/msg10007.html>

+ ath10k-firmware: QCA4019 hw1.0: Add AVM FRITZ!Repeater 3000 specific BDFs
 <https://www.mail-archive.com/ath10k@lists.infradead.org/msg10101.html>

+ ath10k-firmware: IPQ4018 hw1.0: Add EnGenius ENS620EXT specific BDFs
<http://lists.infradead.org/pipermail/ath10k/2019-March/013034.html>

+ ath10k-firmware: QCA9984 hw1.0: Update Netgear Orbi Pro SRK60 specific BDFs
  ath10k-firmware: QCA4019 hw1.0: Update Netgear Orbi Pro SRK60 specific BDFs

  One for QCA9984 and one for two QCA4019
<https://www.mail-archive.com/ath10k@lists.infradead.org/msg10170.html>
<https://www.mail-archive.com/ath10k@lists.infradead.org/msg10171.html>

+ ath10k-firmware: IPQ4019 hw1.0: Add BDF for Linksys EA8300 [1/2]
  ath10k-firmware: QCA9888 hw1.0: Add BDF for Linksys EA8300 [2/2]

<http://lists.infradead.org/pipermail/ath10k/2019-May/013403.html>
<http://lists.infradead.org/pipermail/ath10k/2019-May/013404.html>

Cheers,
Christian