netdev - Re: [RFC PATCH 2/2] mac80211: use the new drop reasons infrastructure

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Message-ID: <3529dbe11a6067f0e959beab77762c74365ae2e7.camel@sipsolutions.net>
Date:   Thu, 30 Mar 2023 10:14:18 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] mac80211: use the new drop reasons
 infrastructure

On Wed, 2023-03-29 at 21:05 -0700, Jakub Kicinski wrote:
> On Wed, 29 Mar 2023 23:46:20 +0200 Johannes Berg wrote:
> > +	/** @SKB_DROP_REASON_SUBSYS_MAC80211_UNUSABLE: mac80211 drop reasons
> > +	 * for unusable frames, see net/mac80211/drop.h
> > +	 */
> > +	SKB_DROP_REASON_SUBSYS_MAC80211_UNUSABLE,
> > +
> > +	/** @SKB_DROP_REASON_SUBSYS_MAC80211_MONITOR: mac80211 drop reasons
> > +	 * for frames still going to monitor, see net/mac80211/drop.h
> > +	 */
> > +	SKB_DROP_REASON_SUBSYS_MAC80211_MONITOR,
> 
> heh, didn't expect you'd have two different subsystems TBH
> 

Hah, me neither!

But then when I came to implement it, I wanted to use some bit in the
reason for he drop/unusable distinction. In fact I did that at first,
until I got to the string list, and realised that no matter how I sliced
it, I'd always have a very sparse array there. If I use the lowest bit
it'd be as compact as possible, but I'd expect the two spaces to not be
equivalently filled, so I'd still get a whole bunch NULLs in the array.

So then I switched to using two subsystems, since that way we have two
distinct string lists.

johannes