Re: [PATCH V3 0/2] brcmfmac: initial work for adding monitor mode

[Arend van Spriel <arend.vanspriel@broadcom.com>]

On 6/24/2018 4:20 PM, Rafał Miłecki wrote:
> On Fri, 22 Jun 2018 at 20:59, Arend van Spriel
> <arend.vanspriel@broadcom.com> wrote:
>> On 6/19/2018 10:25 PM, Rafał Miłecki wrote:
>>> On 2018-06-19 22:01, Arend van Spriel wrote:
>>>> On 6/19/2018 5:48 PM, Rafał Miłecki wrote:
>>>>> From: Rafał Miłecki <rafal@milecki.pl>
>>>>>
>>>>> After a bit long discussions in various e-mail threads I'm coming with
>>>>> this simple & small patchset. It isn't complete support for monitor mode
>>>>> but just a pair of preparing patches that should be clear & well
>>>>> discussed by now to make them acceptable.
>>>>>
>>>>> The main missing bit is code setting MONITOR_FMT_RADIOTAP which I expect
>>>>> Arend to handle soon, as he already has a patch using "sta_monitor"
>>>>> iovar for that. Then we have to discuss a flag for marking firmwares
>>>>> which are capable for tagging monitor frames.
>>>>>
>>>>> While still incomplete, I believe that with my previous patches, we can
>>>>> agree this is a good direction.
>>>>>
>>>>> Arend: if you find these 2 patches OK, could you ack them, to make it
>>>>> clear for Kalle if they look OK now (or not yet)? I'd be great if you
>>>>> could sent your "sta_monitor" work on top of this.
>>>>
>>>> I acked them and I will submit my changes later. Either after these
>>>> are applied or simply indicate the dependency.
>>>>
>>>> Now as for where we are with this. With what we have here we know
>>>> firmware can monitor packets with and without radiotap. However, we do
>>>> not have an indication whether firmware can transport these monitor
>>>> packets to the host. What I need to look into next is whether the
>>>> 802.11 flag in msgbuf is linked to a particular version of the
>>>> protocol, but we may need to resort to the fwid table.
>>>
>>> Being able to detect if firmware tags monitor packets would be great.
>>
>> The 802.11 tag as opposed the 802.3 tag is specified in the PCIe host
>> interface spec. The brcmfmac driver support rev 5 and 6 of that spec and
>> both specify the tags. I did some digging and I believe it is safe to
>> say that firmware that includes the "monitor" tag in the "cap" iovar
>> does support these packets tags as well.
>
> OK, this is nice. The problem is we still need some fallback for the
> old firmwares. Only the newest ones specify "monitor" tag in the "cap"
> iovar. Older firmwares don't specify it but they still may include
> support for monitor mode and radiotap header.

So in your list of firmwares, do you know (or can you find out :-p ) 
which ones return "monitor" and which do not? My educated guess was that 
only firmwares returning "monitor" tag have host-interface code in place 
to send monitor packets up to the host. You may prove me wrong.

Regards,
Arend