[elrepo] USB wireless adapter not working (4.15)

[Alan Bartlett]

On 15 March 2018 at 16:54, Mahmood Naderan <mahmood.nt at gmail.com> wrote:
> Hi,
> I upgraded the default 3.10 on centos 7 to 4.15 via the elrepo rpm
> packages. I have a D-Link DWA 123 wireless dongle which is working on
> ubuntu with kernel 4.10. However, with centos 7 it doesn't work and
> the blue LED is off. As I attach the adapter, I see the following
> messages in the log
>
<snip>
>
> Any idea to fix that? Does kernel correctly load the module?
>
> Regards,
> Mahmood

My suggestion is that you --

* First upgrade to kernel-ml-4.15.10-1.el7.elrepo, which was released
yesterday. [1]

* Once the system has been rebooted and with the wireless dongle
unplugged, capture the state of the USB sub-systems; lsusb > usb-1.txt

* Now plug in the USB wireless dongle and, once again capture the
state of the USB sub-systems; lsusb > usb-2.txt

* Perform a diff on those two textual files and note the Vendor and
Device ID pairing for the wireless dongle.

* Perform a "double grep" on the modules.alias file for the Vendor and
Device ID pairing. Note the module name displayed, if any.

Real-world example --

[Duo2 tmp]$ lsusb > usb-1.txt
[Duo2 tmp]$ lsusb > usb-2.txt
[Duo2 tmp]$ diff usb-1.txt usb-2.txt
0a1
> Bus 002 Device 002: ID 0b95:7720 ASIX Electronics Corp. AX88772
[Duo2 tmp]$ grep -i 0b95 /lib/modules/$(uname -r)/modules.alias | grep -i 7720
alias usb:v0B95p7720d*dc*dsc*dp*ic*isc*ip*in* asix
[Duo2 tmp]$

The Vendor and Device ID pairing for the device used in my example is
0b95:7720 and, via the double grep, we see that the asix module is
required.

With the required module known, it should be easy to see if it has
been loaded; lsmod | head

Alan.

[1] http://lists.elrepo.org/pipermail/elrepo/2018-March/004164.html