Android Ramblings, Craigslist Adventures, Technical Nonsense

Finally found the need to have a real laptop available, so I went out and picked up a MacBook Air over the Thanksgiving break. Since I’ve gotten so used to XMonad for day to day use, it would have to be running Ubuntu. Turns out that there is an Ubuntu community wiki page available detailing what is necessary to get things going.

A script available on almostsure creates a bootable USB drive to install off of, and the almostsure post-install script takes care of installing most of the drivers and configuration you’d want. For reference, the important things (as of Nov 30, 2011) are the following:

1. i915 module fix, without which kernel modesetting doesn’t work.
2. bcm5974 module fix for the trackpad.
3. btusb module for bluetooth, which for some reason doesn’t seem to be working with 11.10 out of the box.
4. hid-apple module for keyboard, for what I assume is backlighting and function keys.
5. xf86-input-mtrack Xorg input module, without which trackpad gestures (two finger scroll, etc) don’t seem to work correctly.
6. dispad package for touchpad pausing, although I haven’t noticed it coming into use.
7. macfanctld package for the fan control daemon, since the default 11.10 package doesn’t seem to do much out of the box.
8. custom xmodmap to remap the Apple key to Alt, Alt/Option to Mod4, since my fingers expect that sort of layout.
9. i915 power saving mode on boot, appending i915.i915_enable_rc6=1 to GRUB_CMDLINE_LINUX_DEFAULT.
10. Avoid the long bootloader timeout by executing: sudo bless —device /dev/disk0s4 —setBoot —legacy from the OS X recovery USB drive.

The one thing NOT covered by the Ubuntu community wiki is the wireless driver. The MacBook Air 4,1 has a Broadcom BCM43224 chip, which is actually covered by several different drivers, b43 (if you hack around a bit), brcmsmac, and the wl Broadcom STA driver (closed source). Poking around seems to suggest that the best option is the brcmsmac module, as it is based off the open-sourced driver that Broadcom released late 2010, however owing to it’s immaturity, it still lives in the staging drivers section of the Linux kernel. It also seems to lack some features supported by the Broadcom STA drivers, namely power management, which is the main reason why I chose to use the closed source (the horror) Broadcom STA drivers available from the Ubuntu “restricted” repository under the brcmwl-kernel-source package.

The one item to note with this module is that the brcmwl-kernel-source package actually doesn’t have an updated blacklist file in /etc/modprobe.d, and will fail to blacklist the brcmsmac module available by default, potentially leading to problems. I had to add brcmsmac and bcma to the blacklist with the following:

sudo sh -c "echo 'blacklist brcmsmac' >> /etc/modprobe.d/blacklist-b43.conf"
sudo sh -c "echo 'blacklist bcma' >> /etc/modprobe.d/blacklist-b43.conf"

This prevents the kernel from loading both drivers. Most of this information was found on the ArchLinux Broadcom wireless wiki page. And that concludes all the laptop configuration I had to do. All that remains is reconfiguring my XMonad settings for laptop use!

I took the plunge and upgraded my main machine to 11.10 from 11.04 today. Altogether not too bad since underneath the much maligned Unity lies compiz and ccsm still configures everything I actually care about. The one thing that did break on upgrade however was my sound. I happen to have a Sound Blaster X-Fi Titanium HD (etc etc), which according to Google searches, seems to be the source of quite a few people’s headaches. Specifically, the X-Fi Titanium HD is recognized by the snd_ctxfi driver, but prior to approximately 6/14/2011, it was recognized as an older model, which caused improper behavior, and if you were quick on the kernel logging, yielded messages similar to these:

[ 4881.961765] SB-XFi 0000:02:00.0: setting latency timer to 64
[ 4918.787949] SB-XFi 0000:02:00.0: PCI INT A disabled
[ 4918.787955] ctxfi: Something wrong!!!
[ 4918.787969] SB-XFi: probe of 0000:02:00.0 failed with error -1

Quick check on gmane.linux.alsa.devel shows that this fellow Harry Butterworth has put a lot of effort into patching up the driver to support the new card in these messages. The ALSA project’s git repositories show that these three patches are required to make things work:

Patch1

Patch2

Patch3

Now that I have the requisite background info, it’s time to get to solving the problem. At the time of this writing (10/14/2011), the version of the Linux kernel package Oneiric uses is 3.0.0-12.20 (full package: linux-image-3.0.0-12-generic). Let’s start off by fetching the source for the kernel with:

sudo apt-get install linux-source

This places the Ubuntu kernel source at /usr/src. We need to go there and unpack it somewhere useful.

mkdir ctxfi-module
cd ctxfi-module
cp /usr/src/linux-source-3.0.0.tar.bz2 .
tar xfj linux-source-3.0.0.tar.bz2

We now need to patch the unpacked kernel source with the proper patches from above. In this version of the source (linux-source-3.0.0-12.20), patch 1 has already been included.

patch -p1 < /path/to/patch2     
patch -p1 < /path/to/patch3

We need to now build our new kernel module. I found useful directions at the Ubuntu wiki page on custom kernel builds. Before doing that however, I noticed my current linux-headers package didn’t have the PCI_ID for the X-Fi Ti HD, so I added this line:

#define PCI_SUBDEVICE_ID_CREATIVE_SB1270 0x0062

to

/usr/src/linux-headers-`uname -r`/include/linux/pci_ids.h

file at line 1308, as in patch 1. Then I followed the make directions in from the Ubuntu wiki.

make -C /usr/src/linux-headers-`uname -r` M=`pwd` KBUILD_SRC=`pwd`/../../.. modules
sudo make -C /usr/src/linux-headers-`uname -r` M=`pwd` KBUILD_SRC=`pwd`/../../.. modules_install
sudo depmod -a
sudo update-initramfs -u

This installed the snd_ctxfi.ko module to:

/lib/modules/`uname -r`/extra/snd_ctxfi.ko

From there it’s a simple matter to rmmod snd_ctxfi and insmod your newly patched one. This got sound working for me again.