QCA9377 monitor mode firmware support

[Guilherme Rios]

Hi,

Is there any particular reason monitor mode firmware support was
dropped from QCA9377?

I did some tests on an IdeaPad 320 laptop running Ubuntu 20.04, with
different firmware versions obtained from
https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/
, and here is what I found:

- Up until commit dd5fba3a56bbb4c4a72576faa19f8bd45fed7ef6, monitor
mode was working (I have seen reports that packet injection was never
supported for this particular chipset; as my use case does not involve
this, I didn't care testing to confirm);

- Starting from 56e5de3261877e5ca9df285e0751368c72b0861a, the driver
behaves as if monitor mode is supported: airmon-ng reports
successfully setting the card to monitor mode, and airodump-ng acts as
if it is collecting data, but no output is ever shown.

I have traced the issue to files firmware-5.bin and firmware-6.bin,
which were respectively updated and created by that commit (board.bin
and board-2.bin were not changed by it).

It called my attention that the message associated to the commit that
dropped monitor mode support was "[e]ven though the version number
suggests that this is an older firmware release it's actually more
recent as this is from a different branch."

Any chance monitor mode support was accidentally lost in this branch,
or was this change made by design?

Are there any issues I should be aware of, if I choose to downgrade
the firmware in order to keep monitor mode support?

Thanks,

Guilherme