OpenBSD and Lenovo Thinkpad T410 Wireless Firmware

I am trying to get my Lenovo Thinkpad T410 working with OpenBSD as a daily driver. One problem I faced, is that the wifi card is not working properly: it is recognized during the installation procedure as iwn0, but the installer is not able to configure it properly.
This would be a simple task to solve if I had ethernet connectivity, that I didn’t!
Since I was installing OpenBSD other mobile phone tethering, how to fix it?
The solution was:

• download the proprietary firmware and place it into an USB stick;
• install without internet connectivity;
• extract the firmware from the USB stick and place it on the computer;
• configure the network adapter.

It could be possible to install the firmware before the installation starts, by going to a shell, but unluckily I was unable to find out the USB stick on my laptop (see later). I mean, it was recognized as sd1 from sysctl hw.disknames (where sd0 was the other USB stick I was running the installation image from), but I was unable to get partition information from such disk, probably because I had to create the device myself.
I therefore decided to continue with the installation, then rebooted the machine and got to the command prompt.
Once I plugged the USB stick, recognized as sd0, I ran disklabel sd0 that shown that the partition I was looking for was the i. I then mounted it with mount /dev/sd0i /mnt and copied the firmware I downloaded from % http://firmware.openbsd.org/firmware/7.0/iwn-firmware-5.11p1.tgz on the local disk. I made the tarball to add the files to /etc/firmware.
I then configured /etc/hostname.iwn0 and rebooted, and the computer became online!

Installing the firmware within the installation process

I tried it different times and came to the conclusion that, at least for a single piece of firmware, it is not worth at all.
Why?
Because I have to install it just before rebooting to complete the installation, so at that late point I can simply log in my new installation and add it manually with all the ease of standard tools without having to manually create nodes, mount, etc. (that is not that hard, however).