PortingGuideS5PC110¶

This guide assumes your phone has a S5PC110/Exynos 3110 SoC

Prerequisites¶

Before porting your device to Replicant, you must make sure it complies with the following:

• Already supported by CyanogenMod (or, worst-case scenario, by a non-official CyanogenMod port)
• CyanogenMod support for this device is available for one of Replicant versions (pick the latest)
• The phone is GSM: Replicant doesn't support CDMA phones yet
• It is likely to be usable without blobs nor firmwares and with Replicant replacements

Investigating the phone hardware¶

Before doing anything, you will need to know the codename of the device. You can find it out on CyanogenMod Wiki or on CyanogenMod download page.
For instance, the Nexus S codename is: crespo.

One very important step is to find out if the device is Tivoized: that means that even though the manufacturer releases the kernel source code for the device, the bootloader checks the kernel signature and will refuse to start it if it's not properly signed by the manufacturer. In other words, if you build the kernel yourself, the device will refuse to run it since it's not signed by the manufacturer. Since the Linux kernel is released under the GPLv2, there are no specific dispositions to counter Tivoization, and so porting the device to Replicant is pointless as it will require a prebuilt and signed kernel from the manufacturer.

First thing to consider before starting a port, when all of the above is assumed, is to see how many non-free components are required by CyanogenMod.
The easiest way to do this is to spot the device repository in CyanogenMod repos and look for the extract-files.sh or proprietary-blobs.txt file.
For instance, the list of non-free components for the Nexus S is extract-files.sh

From that list, spot what is related to what hardware component (audio, camera, sensors, gps, modem, etc): that gives an idea of the amount of work required to add support for the phone.

During the port, you might need to find precise infos about the hardware that is in the phone. A good to do this is by looking at the kernel defconfig for the device, another way is to download the Service Manual for the device.

Getting everything ready¶

In order to prepare everything for the Replicant port:

• Install CyanogenMod on the phone
• Install the BuildDependencies
• Get the sources: GettingReplicantSources
• Read Replicant developer guide: DeveloperGuide
• Learn how to do debug: GettingLogs GDBDebugging

Cloning the device files¶

Once your Replicant tree is ready, you can start by adding the necessary repos for your device.
That means cloning the necessary repos in the right place. These repos are:

• A device-specific repo. On CyanogenMod, it is usually called: android_device_vendor_device.
• Sometimes one or more common repo(s), usually called: android_device_vendor_devices-common.
  Some devices don't need any common repo, but some do.
• A kernel repo. On CyanogenMod, it is usually called: android_kernel_samsung_devices.
  The kernel repo can be shared across a family of devices (for instance, on kernel repo for Samsung Exynos, one for Samsung OMAP, etc).
  If there are different branches in the kernel repo, be sure to use the one that will match userspace: if you are porting to ICS, take the branch called ics or ask the people who know which branch to use.
  Generally speaking, the following kernel versions match the given userspaces:

Android version	CyanogenMod version	Kernel version
Android 2.3	CM 7.x	2.6.35
Android 4.0	CM 9.x	3.0.8
Android 4.1	CM 10	3.0.31
Android 4.2	CM 10.1	3.4

Sometimes, these repos aren't held in CyanogenMod repos but instead in some other projects repos, such as:

• Teamhacksung (Samsung devices)
• FreeXperia (Sony Ericsson Xperia devices)

Generally speaking, it is a good idea to ask the members of the CyanogenMod community where to find what (especially for kernel sources and for which branch to use).

Clone these repos in the correct locations and remove the prefix (e.g. android_device_samsung_crespo must be cloned in device/samsung/ and renamed to crespo).

Creating the kernel repo¶

If the kernel repo is nowhere to be found, you'll need to get the kernel source directly from the vendor, especially if your device is supported by a 3rd party CyanogenMod fork.
Keep in mind that the Linux kernel is GPLv2, so vendors have the legal obligation to release the modified kernel sources as soon as they sell you the device.
That means the kernel sources will be available online. Here are some websites where such releases are done:

• Samsung Open Source Release Center
  For Samsung kernels. Search the device codename (e.g. I9000) and download the package called "Opensource Update" (e.g. GT-I9000_Opensource_GB_Update2.zip).
  This will hold a kernel archive with all the sources and instructions on how to build it and which defconfig to use.
• CodeAurora
  For MSM/QSD devices, and particularly HTC ones.
• HTCdev
• Motorola Sourceforge
• Sony Mobile Developer
• LG OpenSource

Once you have the kernel sources, read the instructions to find out which defconfig to use.

Since manufacturers usually don't release the git history along with the files, you'll need to recreate a git repo:

• Clone the mainline kernel in the same version as the Makefile from the sources you just obtained
• Remove the cloned files except the .git directory
• Move the manufacturer kernel tree at the place of the files you just removed
• Add all the files in git (git add -A) and commit (git commit) with a message explaining what you just imported (e.g. "GT-I9000 GB Opensource Update 2")

Now that you have a git repo, you can move it to the Replicant code tree, under the name: kernel/vendor/devices (e.g. kernel/samsung/aries).
Make sure to make the devices name match the devices in android_device_vendor_devices-common if the kernel is shared across these devices or to match the device in android_device_vendor_device.

Adding the device to the build targets¶

Now that the repos are cloned, you need to modify some makefiles to cope with Replicant paths.
In the device repository (device/vendor/device), modify the file called cm.mk and replace the vendor/cm/ occurrences by vendor/replicant/. Other makefiles may need that as well (in any case, build will fail very early if you missed one). In that same cm.mk file, change the PRODUCT_NAME variable by repalcing the cm prefix with replicant (e.g. change PRODUCT_NAME := cm_crespo to PRODUCT_NAME := replicant_crespo).

Now that your device files are ready, you can declare a new build target: these are held in vendor/replicant/jenkins-build-targets.
Modify that file and add a line (at the end) with the PRODUCT_NAME you set and the -eng suffix (e.g. replicant_crespo-eng).

From now on, everything should be ready to start a build. To check for errors or missed occurrences, start a terminal in the Replicant tree root and lunch:

source build/envsetup.sh
lunch replicant_device-eng

Adapt replicant_device-eng from what you added to the jenkins-build-target (e.g. replicant_crespo-eng).
If an error occurs, it will explicitly report it and you'll need to fix it before doing anything.
If everything works correctly, you should see something like:

============================================
PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=4.0.4
TARGET_PRODUCT=replicant_crespo
TARGET_BUILD_VARIANT=eng
TARGET_BUILD_TYPE=release
TARGET_BUILD_APPS=
TARGET_ARCH=arm
TARGET_ARCH_VARIANT=armv7-a
HOST_ARCH=x86
HOST_OS=linux
HOST_BUILD_TYPE=release
BUILD_ID=IMM76L
============================================

In case of a prebuilt kernel¶

Some devices are still using a prebuilt kernel. Even though the CyanogenMod team is trying to avoid that, it remains in many repos.
For such devices, you will need to remove the prebuilt binaries and the instructions to copy the prebuilt kernel and its modules.

Building the kernel¶

Once the devices repos are in place and the build target is configured, you are now able to start building things and the first thing to build is obviously the kernel.

Various hardware and software fixes to get things working.¶

To get software video decoding (OMX stuff):¶

• remove OMX libs for hardware video decoding
• remove libstagefrighthw.so
  like that: http://gitorious.org/replicant/device_samsung_crespo/commit/c8edb6539977c8820d665691d53c33892cfa4fdd