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QuickDeveloperStartGuide
From Htc-linux
This page will try to help you getting started with development and understand what the elements are.
This is still a draft. Any improvements are welcome. To find more general information on Linux development for embedded devices you can stop by at http://elinux.org
Contents |
[edit] The Basics
The system on a pxa is not much different from a standard PC. In fact (beside cross compiling and if the kernel supports the hardware, you can even run some desktop distributions on it...)
To run Linux on a phone you'll need:
- A boot loader that loads the kernel into memory and runs it.
- A Kernel which is responsible to access the hardware and let applications communicate with it.
- Daemons and utilities that make the system available to user space
- And there is a GUI or commandline which is responsible for user interaction.
Once most of this works your phone could be used.
Source(s): QuickDeveloperStartGuide
[edit] Bootloader
The developers use mainly HaRET which is a bootloader and a tool used to analyse your phone hardware.
This tool runs from Windows Mobile. It won't replace the system or anything on the phone.
There is also Linload used on some htc phones. It is used to only start the kernel directly.
First thing the bootloader needs to know where to load the kernel and run it.
[edit] Kernel
[edit] Obtaining source code and building the kernel
Using htc vogue in this example. For HD2 aka leo use branch 'htc-msm-2.6.32' and config 'htcleo_defconfig'
Obtaining the source code
First chose a kernel repository and branch for your device.
get a local copy of the kernel repository
git clone git://git.linuxtogo.org/home/groups/mobile-linux/kernel.git
cd kernel
list branches
git branch -a
you will see that a branch named htc-vogue exists on the remote repository
'remotes/origin/htc-vogue'
check that branch out
git checkout -b htc-vogue origin/htc-vogue
optional: see below for how to check out a specific revision/commit of the source code
Configuring the kernel
There are default configurations for many devices included in the kernel sources. Show a list of available kernel configurations chose the one that suites your device best
make ARCH=arm help
Write the default kernel configuration for your device from arch/arm/configs/vogue_defconfig to .config
make ARCH=arm vogue_defconfig
optional: If you want to edit the default configuration run
make ARCH=arm menuconfig
Compiling the kernel
sometimes it is necessary to remove your already compiled files and build from scratch
make clean
let's start compiling. CROSS_COMPILE= env var is important. read more about it on toolchain page.
zImage will give you a gzipped kernel image. to produce uncompressed one simply put 'Image' instead
make ARCH=arm CROSS_COMPILE=/path-to-toolchain/bin/arm-linux-gnueabi- zImage
The product will be written to arch/arm/boot/zImage
On most htc devices you will need HaRET to boot it.
Compile and installing the kernel modules
In many cases the Linux kernel is configured to use modules. Drivers that are not included in the Image / zImage and which must be installed into your rootfilesystem.
Compiling the kernel modules
make ARCH=arm CROSS_COMPILE=/path-to-toolchain/bin/arm-linux-gnueabi- modules
Install the modules into your rootfilesystem
make ARCH=arm INSTALL_MOD_PATH=/mountpoint/of/your/rootfilesystem modules_install
Staying up to date To obtain code updates run
git pull
To clean any local changes use
git reset --hard
Checking out a specific revision/commit of the source code
optionally, before builing you can checkout a specific source revision to view a commit overview of the current branch use
git log
to show the source revision at a specified date use this
git rev-list htc-vogue -n 1 --first-parent --before=2010-03-11
this will give you the hash for that commit
497da7f2f1a9040d3000eedd08d6caff4eaba4e8
move to the desired revision (removing any locally made changes)
git reset --hard 497da7f2f1a9040d3000eedd08d6caff4eaba4e8
Monitoring local changes
git status
Creating patches
git format-patch
For a more in-depth look at kernel development and collaboration in git, see AdvancedGitGuide.
[edit] Linux OS / Embedded distributions
This usually is included in the distribution. (Angstrom, Android, Openmoko, etc)
Usually they have an init system and basic utilities (libc, binutils, openssh, etc. or an equivalent embedded version uclibc, busybox, etc.)
[edit] OpenEmbedded (OE)
[edit] Angstrom
[edit] Openmoko
