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Subject: Re: [PATCH] mac80211: report per-chain signal values through ethtool.
To:     Johannes Berg <johannes@sipsolutions.net>,
        linux-wireless@vger.kernel.org
References: <20220329210228.8137-1-greearb@candelatech.com>
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 <d383ef715a7186cb382ff9450878747b8384dd0f.camel@sipsolutions.net>
From:   Ben Greear <greearb@candelatech.com>
Organization: Candela Technologies
Message-ID: <72db23af-3d04-252c-c728-0c71fab8dbcb@candelatech.com>
Date:   Fri, 1 Jul 2022 06:18:14 -0700
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On 7/1/22 6:08 AM, Johannes Berg wrote:
> On Fri, 2022-07-01 at 06:05 -0700, Ben Greear wrote:
>> On 7/1/22 2:55 AM, Johannes Berg wrote:
>>> On Tue, 2022-03-29 at 14:02 -0700, greearb@candelatech.com wrote:
>>>> From: Ben Greear <greearb@candelatech.com>
>>>>
>>>> Combine them into a u64, each byte is one chain.
>>>
>>> This only works up to 4 chains, but the specs at least support 8. I
>>> don't think we have any drivers for that, but ...
>>
>> u64 gives 8 bytes, so the ethtool part can support 8 chains.
>> The mac80211 part only supports up to 4 chains currently though.
> 
> Oops, right, sorry.
> 
> Still, I'm not sure I like munging it all up into one value - the value
> itself then doesn't mean anything, and the normal ethtool APIs userspace
> tools would be pretty much useless for it?

A human looking at the value would be confused, but a program easily deals
with it.  In a lot of ways, ethtool is way more straight forward to program
against than netlink, and it works well with non-wifi drivers, so one
chunk of stats-gathering code for all network devices.

> 
>>> We're reporting these through nl80211 anyway though, no? Why should we
>>> prefer ethtool, which fundamentally limits to a single value for the AP
>>> rather than giving the full per-station view.
>>
>> I already gather ethtool stats for STA vdevs, so adding another stat is
>> basically free as far as performance is concerned.  That is important
>> to me.  I do not currently program much against netlink API (just scrape
>> existing tools output).
> 
> Well I guess then I think you probably should program against the
> netlink API :)

I've managed to mostly dodge it for 20 years....there is hope to make it another 20!

> 
>>>> Re-work the way that APs averaged stats to be more
>>>> efficient.
>>>
>>> Isn't that completely unrelated?
>>
>> At least somewhat unrelated.
>>
> 
> Fair enough. Maybe send that separately? I guess that's something I'd
> understand a bit more and improving the existing code is an easier sell
> than adding a whole new thing there :)

Ok, I'll add that to my list and will plan to do it next time I rebase on
a newer upstream kernel.

Thanks,
Ben

> 
> johannes
> 


-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com