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Subject: Re: [PATCH v2 1/4] mac80211: Rearrange ieee80211_tx_info to make
 room for tx_time_est
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Toke =?ISO-8859-1?Q?H=F8iland-J=F8rgensen?= <toke@redhat.com>,
        Kan Yan <kyan@google.com>
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        Lorenzo Bianconi <lorenzo@kernel.org>,
        Felix Fietkau <nbd@nbd.name>,
        Rajkumar Manoharan <rmanohar@codeaurora.org>,
        Kevin Hayes <kevinhayes@google.com>
Date:   Fri, 18 Oct 2019 16:07:20 +0200
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On Fri, 2019-10-18 at 16:01 +0200, Toke Høiland-Jørgensen 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.

> > > We could also split 5/11. That would support up to 32 ACK IDs, and we
> > > can just truncate the airtime at 2048 us, which is not a big deal I'd
> > > say.
> > 
> > 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?
> 
> 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).
> 
> 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.

johannes