Downgrading iwlwifi

Question

I asked this question, but I'm becoming more and more certain that my problem stems from a faulty iwlwifi firmware version. Rather than muddy the water there, I'd like to ask if it's possible to downgrade my islwifi firmware to a previous version.

If it's possible, can you tell me specifically how? I'm not really great with generic instructions. Or is there a website that I've missed?

Solution 1

The Linux firmware sources are being developed in a Git repository, so it's easy to go back in time for all older releases of the firmware.

1. Install git

2. Clone the repository (cgit web page):

   git clone http://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git
   

3. cd into the repository:

   cd linux-firmware
   

4. Locate the firmware for your device as per the iwlwifi development page or legacy (scroll down), e.g. iwlwifi-3945-2.ucode.

   find . -name "iwlwifi*"
   

   Notice that for some devices multiple versions are kept as separate files, for the compatibility of older kernel versions.

5. Have a look at the history of the file:

   git log iwlwifi-3945-2.ucode
   

   shows (removed some irrelevant lines):

   commit d90a18c9e7eef19ab978c4c0bb2d2d4b8fa49dce
   Date:   Thu May 14 18:15:50 2009 +0100
   
       linux-firmware: Update Intel Wireless Wifi 3945 firmware
   
       Version is now 15.32.2.9
   
   commit caef650a8c909f557ed7f6b23c413401d6994fdb
   Date:   Tue Jan 20 21:37:48 2009 +0000
   
       linux-firmware: Add Intel Wireless Wifi firmware
   

6. The revision at the top is the version in your working directory. To retrieve an older version of the same file, do this:

   git show caef650a8c909f557ed7f6b23c413401d6994fdb iwlwifi-3945-2.ucode > ~/some/destination/iwlwifi-3945-2.ucode
   

   see also: How to retrieve a single file from specific revision in Git?

   However, most firmware files only have a single revision in the repository and are versioned by just having multiple filenames.

7. Install the firmware in /usr/local/lib/firmware (location for manually installed firmware files) by copying the file there:

   sudo cp /path/to/iwlwifi-3945-2.ucode /usr/local/lib/firmware/
   

8. Remove and re-insert the kernel module(s):

   rmmod iwldvm && rmmod iwlwifi
   modprobe iwlwifi && modprobe iwldvm
   

   And look at dmesg to see if the firmware gets loaded.

---

In case you wonder if any files have been removed from the repository, try this:

git log --diff-filter=D --summary | grep delete

At the time of writing, no Intel firmware has been deleted ever.

Solution 2

At

http://wireless.kernel.org/en/users/Drivers/iwlwifi

you can find firmware for Intel wireless chips.

But I don't know if you can find a older version for your specific chip.

Comments

[Carlo Felicione]

Thanks. I'm trying it now, and I'll let you know what happens.

[Carlo Felicione]

The particular firmware still didn't work for me to solve the problem, but the methodology was perfect. (I believe it's a hardware issue and will take it apart soon.) Two questions: (1) I needed to sudo rmmod and modprobe. Is that typical? (2) My firmware was installed in /lib/firmware not /usr/local/lib/firmware. Does it matter? Thanks again!

[Carlo Felicione]

I saw those earlier and definitely used them. I just wanted something earlier if possible. Thanks.

[gertvdijk]

1) Reloading the kernel modules will load the firmware. Just replacing the files won't affect a running system. 2) Not really, it's just a convention to install user-supplied firmwares (not by package management) in /usr/local/lib/firmware (likewise, /usr/local/bin for local-installed binaries). Generally, you should not touch anything in system directories - that will confuse the package management. Be aware that the file will be overwritten on the next package update now!