Re: [Bug] carl9170 + wpa_supplicant: P2P mode doesn't work with separate interfaces

[Christian Lamparter <chunkeey@gmail.com>]

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.

Regards,
Christian