Software projects/OS/Slackware/Advanced usage/Kernel

Kernel: to recompile or not to recompile ?

• You don't have to if you don't need to add a new feature.
• You don't have to if there's no urgent security kernel update.
• If you want to acquire a lot of global Linux knowledge, or if you are just curious, then yes, just go for it.

Is it simple or complicated to recompile ?

• Both.
• But as there's a default kernel configuration file for Open Pandora, it's pretty easy.

Downloading and pre-configuring the latest kernel sources

• Plug the net, be root, then:

mkdir -p /usr/src/
cd /usr/src/
git clone git://openpandora.org/pandora-kernel.git
ln -s pandora-kernel linux
cd pandora-kernel
git checkout --track -b pandora-3.2 origin/pandora-3.2
make omap3_pandora_defconfig

The fun part: tweaking

• The configuration is stored in a hidden file named /usr/src/linux/.config
• You can use many tools to edit the configuration.
• The kamikaze way: edit manually the .config . Don't do that.
• The lazy way: install KDE and use:

make xconfig

• The common way, which i recommend:

make menuconfig

Menuconfig

• Kernel options are stored in a tree.
• Options can be marked as [*] built-in, or <M> module.
• The vast majority of those options refers to a driver or a functionality.
• Built-in means inside the kernel, so once the kernel boots, you can't remove or change parameters.
• Module means you can either add or remove them after the boot. Ever typed "modprobe ehci-hcd" ?
• The exemple below is copied from my PC, will copy the real OP one later.

Arrow keys navigate the menu.  <Enter> selects submenus --->.  Highlighted letters are hotkeys.  Pressing <Y> includes, <N>
excludes, <M> modularizes features.  Press <Esc><Esc> to exit, <?> for Help, </> for Search.  Legend: [*] built-in  [ ]
excluded  <M> module  < > module capable 
[*] DMA memory allocation support
General setup  --->
[*] Enable loadable module support  --->
[*] Enable the block layer  --->
Processor type and features  --->
Power management and ACPI options  --->
Bus options (PCI etc.)  --->
Executable file formats / Emulations  --->
[*] Networking support  --->
Device Drivers  --->
Firmware Drivers  --->
File systems  --->
hacking  --->
options  --->
Cryptographic API  --->
Virtualization  --->
Library routines  --->
<Select>    < Exit >    < Help >

A simple tweak

• Highlight Cryptographic API --->
• Push [enter]. You're now in the Cryptographic API section.
• With [space], select all cryptographic algorithms you can. Ensure they are marked as <M>, not <*>.
• With [right], select < Exit >, then push [enter].
• Again, with [right], select < Exit >, then push [enter].
• Now push [enter], saying <Yes> to "Do you wish to save your new configuration ?".
• You're now ready to compile a kernel which will drive James Bond angrily jealous.

Kernel compilation

• Be sure you've overclocked your OP to the maximum MHz.
• At 800MHz, it's a 3+ hours job.
• Now you can compile it with:

cd /usr/src/linux/
make clean
make uImage
make modules
make modules_install
rm /boot/uImage
cp arch/arm/boot/uImage /boot/uImage

• Reboot.

Speed up the compilation time using two or more Pandoras

• Read this, and set up your Pandoras.
• Then compile, replacing previous related commands with:

make -j4 CC=distcc uImage
make -j4 CC=distcc modules

In the -j(n), n represents the (number of CPU used X 2), so if you compile with 10 OP, it will be -j20 .

3D driver

• As it's not open source, you have to grab it on the Texas Instruments website.
• More on this later.