Public bug reported:
# Miracast/Wi-Fi Display fails with MediaTek MT7612U USB adapter despite
working P2P discovery
## Summary
I am trying to use Ubuntu 26.04's GNOME Network Displays to mirror the
laptop display to a Roku Express 3900 using Wi-Fi Direct/Miracast.
The laptop has an internal Realtek Wi-Fi adapter and a USB MediaTek
MT7612U adapter. The USB adapter is being used specifically for Wi-Fi
Display/P2P.
The MT7612U is correctly detected by Ubuntu, the `mt76x2u` driver loads,
and the adapter advertises P2P-client and P2P-GO capabilities. I was
also able to discover the Roku directly using a standalone
`wpa_supplicant` instance.
However, GNOME Network Displays does not discover the Roku reliably, and
the normal NetworkManager/system `wpa_supplicant` path initially failed
to acquire the MT7612U interface.
## System information
* Ubuntu: 26.04
* Kernel: 7.0.0-31-generic
* GNOME Network Displays: 0.99.0-1
* NetworkManager: 1.54.3
* wpa_supplicant: 2.11
* USB Wi-Fi chipset: MediaTek MT7612U
* USB ID: `0e8d:7612`
* Driver: `mt76x2u`
* Target device: Roku Express 3900
USB identification:
```text
0e8d:7612 MediaTek Inc. MT7612U 802.11a/b/g/n/ac Wireless Adapter
```
Driver information:
```text
driver: mt76x2u
version: 7.0.0-31-generic
firmware-version: 0.0.00-b1
bus-info: 3-1:1.0
```
The adapter appears as:
```text
wlx808c97be890a
```
## P2P capabilities
`iw phy phy1 info` reports support for:
```text
P2P-client
P2P-GO
```
and also reports:
```text
start_p2p_device
```
The reported interface combination includes:
```text
#{ managed, AP, mesh point, P2P-client, P2P-GO } <= 2
total <= 2
#channels <= 1
```
Therefore the hardware/driver does expose Wi-Fi Direct/P2P
functionality.
## Successful direct P2P discovery of the Roku
Using a standalone `wpa_supplicant` instance dedicated to the MT7612U, I
ran:
```text
sudo wpa_cli -i wlx808c97be890a p2p_find 30
```
followed by:
```text
sudo wpa_cli -i wlx808c97be890a p2p_peers
```
The Roku was discovered:
```text
da:31:34:2d:6e:82
```
Querying the peer produced:
```text
device_name=Express
level=-56
listen_freq=2437
oper_freq=0
status=0
```
This demonstrates that the MT7612U/`mt76x2u` path is capable of
detecting the Roku's P2P device.
## GNOME Network Displays behavior
GNOME Network Displays starts normally but does not discover the Roku
through the expected NetworkManager-managed P2P path.
The application reports that the P2P device associated with the MT7612U
is not yet available and waits for it.
The internal Wi-Fi adapter creates a usable P2P device and GNOME Network
Displays can see other P2P devices such as HP/Brother printers, but the
Roku is not discovered through this path.
## NetworkManager / wpa_supplicant problem
Initially NetworkManager reported the MT7612U as:
```text
wlx808c97be890a wifi unavailable
p2p-dev-wlx808c97be890a wifi-p2p unavailable
```
NetworkManager repeatedly reported:
```text
Couldn't initialize supplicant interface:
GDBus.Error:fi.w1.wpa_supplicant1.UnknownError:
wpa_supplicant couldn't grab this interface.
```
At the same time, the system `wpa_supplicant` reported that the control
socket for the MT7612U already existed and appeared to be in use.
This was ultimately traced to a manually launched standalone
`wpa_supplicant` instance that had previously been used for the P2P
test. After terminating that process and removing the stale state, the
normal NetworkManager path was able to acquire the interface.
## Current/clean NetworkManager result
After toggling the device from unmanaged to managed:
```text
sudo nmcli device set wlx808c97be890a managed no
sudo nmcli device set wlx808c97be890a managed yes
```
NetworkManager successfully changed the MT7612U to:
```text
wlx808c97be890a wifi disconnected
```
and created:
```text
p2p-dev-wlx808c97be890a wifi-p2p disconnected
```
The NetworkManager journal contained:
```text
supplicant interface state: internal-starting -> disconnected
```
then:
```text
Wi-Fi P2P device controlled by interface wlx808c97be890a created
```
and:
```text
device (wlx808c97be890a):
state change: unavailable -> disconnected
(reason 'supplicant-available')
```
A corresponding wpa_supplicant control socket was created:
```text
/run/wpa_supplicant/wlx808c97be890a
```
Therefore the normal system `wpa_supplicant` can successfully acquire
and manage the MT7612U after the stale/competing supplicant state is
cleared.
## Why I am reporting this
The important observation is that the problem does not appear to be
simple hardware detection or lack of P2P support.
The following layers have been demonstrated to work:
```text
MT7612U hardware
↓
mt76x2u kernel driver
↓
P2P capability
↓
standalone wpa_supplicant
↓
Roku P2P discovery
```
NetworkManager can also eventually create and manage the corresponding
P2P device.
The unresolved failure is the complete integrated Miracast path:
```text
GNOME Network Displays
↓
NetworkManager
↓
system wpa_supplicant
↓
MT7612U / mt76x2u
↓
Wi-Fi Direct / P2P
↓
Roku Express 3900
```
GNOME Network Displays still fails to discover/connect to the Roku
through the normal desktop networking stack.
I would appreciate guidance on whether this is a known limitation or bug
involving:
* GNOME Network Displays
* NetworkManager's P2P handling
* wpa_supplicant P2P integration
* `mt76x2u` P2P operation
* or the interaction between multiple Wi-Fi PHYs/interfaces when one is used
for normal Wi-Fi and another for Miracast.
The system has two independent Wi-Fi PHYs:
```text
phy0: wlp1s0
phy1: wlx808c97be890a
```
The internal adapter remains connected to the normal Wi-Fi network while
the MT7612U is intended for Miracast/P2P.
## Additional observation
The kernel/wpa_supplicant logs also contained repeated:
```text
nl80211: kernel reports: Match already configured
```
during the period when the MT7612U could not be acquired by the system
`wpa_supplicant`.
It is unclear whether this is merely residual state from the earlier
standalone `wpa_supplicant` process or indicates a deeper P2P/nl80211
state-management problem.
## Expected behavior
GNOME Network Displays should be able to discover the Roku Express 3900
through the MT7612U USB adapter and establish a Wi-Fi Display/Miracast
session while the internal Wi-Fi adapter remains connected to the normal
network.
## Actual behavior
The MT7612U is detected and supports P2P, and direct P2P discovery using
standalone `wpa_supplicant` can find the Roku, but GNOME Network
Displays does not discover/connect to the Roku through the normal
integrated Ubuntu networking stack.
## Reproduction hardware
USB adapter:
```text
MediaTek MT7612U
USB ID: 0e8d:7612
Driver: mt76x2u
```
Target:
```text
Roku Express 3900
```
Software:
```text
Ubuntu 26.04
Linux 7.0.0-31-generic
GNOME Network Displays 0.99.0-1
NetworkManager 1.54.3
wpa_supplicant 2.11
```
** Affects: gnome-network-displays (Ubuntu)
Importance: Undecided
Status: New
--
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https://bugs.launchpad.net/bugs/2169479
Title:
Miracast/Wi-Fi Display fails with MediaTek MT7612U USB adapter despite
working P2P discovery
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