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Subject: Re: [Bug] carl9170 + wpa_supplicant: P2P mode doesn't work with
 separate interfaces
To:     Christian Lamparter <chunkeey@gmail.com>
Cc:     chunkeey@googlemail.com, j@w1.fi, linux-wireless@vger.kernel.org
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 <8972271.5nXPVzACVl@debian64>
From:   =?UTF-8?Q?Frank_Sch=c3=a4fer?= <fschaefer.oss@googlemail.com>
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Date:   Sun, 19 Apr 2020 16:08:23 +0200
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Am 18.04.20 um 18:30 schrieb Christian Lamparter:
> Hi,
>
> On Saturday, 18 April 2020 13:20:27 CEST Frank Schäfer wrote:
>> I'm currently testing Miraclecast
>> (https://github.com/albfan/miraclecast), an open source
>> Wifi-Display/Miracast implementation.
>> In one of my setups, I'm using a carl9170 device as sink, which fails
>> with the following debugging output:
>>
> It's been a very long time. But I do remember meddling with P2P. Part of the
> reason is that the carl9170 driver needed these virtual interfaces initialized
> in a specific order.
>
> So for P2P GO+CLIENT, you would have to initialize the P2P-GO interface first
> and the P2P Client interface second. Which is backwards of what the wpa_supplicant
> does.
>
> Same is true for STA+AP (Repeater). The AP has to start first before the STA
> can be brought up (Also the STA must not interfere with channel operations, as
> the fast channel change feature doesn't work right on the AR9170 Hardware).
>
> This is documented in the driver:
> <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/wireless/ath/carl9170/main.c#n625>
>
> and was changed as part of this commit:
> <https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/net/wireless/ath/carl9170/main.c?id=7f878b0d96e6b3bd27d736fb2fb7e3cc94b16b26>
>
> that identifies the wpa_supplicant commit
> ["nl80211: Automatically use concurrent P2P if possible"] as the reason.
>
> So since this broke, something must have changed since 2012 I guess.
> But I need more details, before I can do something.
Please let me know what you need. :)

Regards,
Frank

> Regards,
> Christian
>