wireless - How to know I have to blacklist acer_wmi?

I recently bought a Xiaomi Notebook Air 13'.

As a lot of people, I met some issues with the WiFi on Ubuntu (16.04). Basically, the WiFi just did not work.

As answered on ask ubuntu, a simple way to fix this issue is to add blacklist acer_wmi in the file blacklist.conf.

So, my question is not "How to fix this issue?", but my question is "How could I know by myself ( ie. just by looking in command output like lsmod or lspci ) how to fix this issue?

For example, an extract of the output of lspci -vv is the following:

$ lspci -vv
02:00.0 Network controller: Intel Corporation Wireless 8260 (rev 3a)
Subsystem: Intel Corporation Wireless 8260
Control: I/O- Mem+ BusMaster+ SpecCycle- MenWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
Status: Cap+ 66Mhz UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- SERR- 
Latency: 0, Cache Line Size: 64 bytes
Interrupt: pin A routed to IRQ283
Region 0: Memory at a4100000 (64-bit, non-prefetchable) [size=8K]
Capabilities: 
Kernel driver in use: iwlwifi
Kernel modules: iwlwifi

Here, we see that iwlwifi is the module which drives the Wifi controller.

But I cannot find any link (when I use for example lspci or lsmod) between iwlwifi and acer_wmi.

But if I blacklist acer_wmi, the WiFi works fine! Why ?

For information:

$ lsmod | grep acer_wmi
acer_wmi       20480 0
sparse_keymap  16384 2 acer_wmi,dell_wmi_aio
wmi            16384 4 acer_wmi,mxm_wmi,dell_wmi_aio,nouveau

video          40930 3 acer_wmi,nouveau,i915

The module iwlwifi is the driver for your wireless device. The module acer_wmi is a helper module that translates key presses, Fn+F8 for example, into action, in your case, 'turn on the wireless radio, please.'

You can gain some clues from the terminal command:

rfkill list all

You may see something like this:

0: phy0: Wireless LAN
    Soft blocked: no
    Hard blocked: no
1: acer-wireless: Wireless LAN
    Soft blocked: yes
    Hard blocked: no

As well, you may notice that any presses of the wireless or airplane mode key doesn't enable wireless. In your case, we also see:

$ lsmod | grep acer_wmi
acer_wmi       20480 0
sparse_keymap  16384 2 acer_wmi,dell_wmi_aio
wmi            16384 4 acer_wmi,mxm_wmi,dell_wmi_aio,nouveau
video          40930 3 acer_wmi,nouveau,i915

The original manufacturer of your Xiaomi is probably not both Acer and Dell.

As an experiment, you blacklisted acer_wmi and the wireless works correctly. I believe you found the correct solution!