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From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
To:     Johannes Berg <johannes@sipsolutions.net>,
        Kan Yan <kyan@google.com>
Cc:     linux-wireless@vger.kernel.org,
        make-wifi-fast@lists.bufferbloat.net, ath10k@lists.infradead.org,
        John Crispin <john@phrozen.org>,
        Lorenzo Bianconi <lorenzo@kernel.org>,
        Felix Fietkau <nbd@nbd.name>,
        Rajkumar Manoharan <rmanohar@codeaurora.org>,
        Kevin Hayes <kevinhayes@google.com>
Subject: Re: [PATCH v2 1/4] mac80211: Rearrange ieee80211_tx_info to make room for tx_time_est
In-Reply-To: <e2c54294fa5ac7b48e6099b47385a5f4df0859ce.camel@sipsolutions.net>
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Date:   Fri, 18 Oct 2019 16:22:14 +0200
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Johannes Berg <johannes@sipsolutions.net> writes:

> On Fri, 2019-10-18 at 16:01 +0200, Toke H=C3=B8iland-J=C3=B8rgensen wrote=
:
>
>> Right. Well in that case, let's try it. As long as we fail in a
>> reasonable way, we can just see if we run into anything that breaks? I
>> guess in this case that means rejecting requests from userspace if we
>> run out of IDs rather than silently wrapping and returning wrong data :)
>
> We can't reject due to how this works, but if the idr_alloc() fails then
> we'll just not give a status back to userspace later.

OK, I guess someone will notice if that suddenly starts happening all
the time ;)

>> > > We could also split 5/11. That would support up to 32 ACK IDs, and w=
e
>> > > can just truncate the airtime at 2048 us, which is not a big deal I'=
d
>> > > say.
>> >=20
>> > We can also play with the units of the airtime, e.g. making that a
>> > multiple of 2 or 4 us? Seems unlikely to matter much?
>>=20
>> Sure, that's a good point! Increments of 4us means we can fit 4ms is 10
>> bits, leaving plenty of space for ACK IDs (hopefully).
>>=20
>> I'll rework the series to use that instead :)
>
> OK.
>
> There are two places that call idr_alloc() with a hardcoded limit of
> 0x10000, you'll have to fix those to have the right limit according to
> the bits you leave for the ACK id.

Yup, found those. Will send a new version of the series in a bit.

-Toke