Re: strange problem with usb wifi adapter
On Sat 11 Dec 2021 at 22:03:41 (+0000), Long Wind wrote:
> David is right, lsusb:
> Bus 002 Device 004: ID 148f:7601 Ralink Technology, Corp. MT7601U Wireless Adapter
>
> i do some interesting test, am able to reproduce my problem,
> it reaffirm my suspicion that it's related to power cutoff,
> something i can't explain because of my limited hardware knowledge
>
> i think my adapter uses mt7601u.bin in /lib/firmware
> i remove firmware-misc-nonfree, wifi works even after reboot
> though /lib/firmware/mt7601u.bin is gone
>
> then i shutdown and unplug power cord and wait for half minute
> i plug power cord and boot, same problem arise
> lsusb can list my adapter, but "ip link" doesn't show it
> and i have to install firmware-misc-nonfree to solve it
Firmware isn't like most software, where it's read from the
filesystem whenever it's needed. It's not even like heavily
used software, where it's kept in cache in memory to avoid
having to read the filesystem so frequently.
What you appear to be describing is a case where the kernel
module loads some firmware into the chips inside the device,
making it work correctly. And until the power is removed
from those chips, the firmware remains in the chips.
In days of yore, many people had to initialise some internal
devices in PCs using DOS, and then perform what was termed
a warm/soft reboot to load linux without losing the effects
of the initialisation.
Cheers,
David.
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