Porting to a new device

Introduction
This is a step by step guide made for you to be able to port postmaketOS to a new device.

The main steps are:


 * Set up postmarketOS development environment on your computer.
 * Build a device-specific kernel and a device-specific system package for your device, or make use of a (close to) mainline kernel and a device-specific system package.
 * Install the system and adapt it according to your device and usage.

For help, simply connect to the main Matrix/IRC channel and kindly drop your question. People are happy to answer your questions!

Before you follow this guide, identify what SoC (System on a Chip) the device you want to port has. We have dedicated mainlining guides for the following SoCs:


 * Snapdragon 410/412 MSM8916/Snapdragon 615/616 MSM8939
 * Snapdragon 820/821 MSM8996
 * Snapdragon 845 SDM845

Even if your SoC isn't listed here, it may have good mainline support. You can try to find yours in SoC Communities and ask for help in postmarketOS mainline on Matrix/IRC.

If your device is supported by a (close to) mainline Linux kernel, it is preferable to port it using that kernel. You will be able to achieve greater hardware support (GPU, modem, and so on) while also having more up-to-date software. In some cases, it can even be easier. However, if your device isn't well-supported by any (close to) mainline kernel, keep reading this guide.

Preparation

 * Search the Devices page for your device to avoid duplicate work. Also search the wiki for your device, and check for links to existing branches. If your target device has an x86-64 CPU, you may be able to use the generic x64 UEFI device port.
 * Join Matrix/IRC to get help when you're stuck.

Requirements


Development environment
To set up a development environment, you will need a GNU/Linux system capable of making builds and running pmbootstrap, our development and installation tool. If you don't have a Linux-based OS installed, you may want to set up a virtual machine with VirtualBox first.

Your GNU/Linux system must have:
 * A few gigabytes of free space
 * Linux kernel 3.17 or newer (since earlier Linux kernels do not support the  syscall).

Knowledge
It is recommended that you at least somewhat know how to use Linux distributions and how to build software as the porting process is a bit harder than just running a few commands.

Target Device
If your target device has an ARM processor, it must have a floating-point unit (FPU). If the device has at least an ARMv7 CPU, it should have an FPU; however, only some ARMv6 CPUs have one.

Most smartphones have an FPU. Of the first 80+ ports that we started, only two phones lacked an FPU: the HTC Wildfire from 2010 and the Vodafone 858 Smart from 2011 ). Both phones use the MSM7225, an ARMv6 SoC. If your phone was made before 2012, make sure it has an FPU.

Initialization
Install pmbootstrap, our lightweight postmarketOS development and installation tool. Then run the following:

Type in the code name of your device to start a new port, and answer each prompt. For help, see how to find device-specific information.

Target device (either an existing one, or a new one for porting). Available (60): asus-flo, asus-grouper, fairphone-fp2, ... Device [samsung-i9100]: wiki-example You are about to do a new device port for 'wiki-example'. Continue? (y/n) [y]: Device architecture (armhf/armv7/aarch64/x86_64/x86) [armhf]: armv7 Who produced the device (e.g. LG)? Manufacturer: Samsung What is the official name (e.g. Google Nexus 5)? Name: Wiki Example Does the device have a hardware keyboard? (y/n) [n]: Does the device have a sdcard or other external storage medium? (y/n) [n]:

Flash method
It depends on the flashing protocol that comes with the device. For most Android devices, this is, some Samsung models need   (which is compatible to "Odin") and Maemo/MeeGo-based Nokia phones work with. If you don't know which one it is, try to enter the bootloader on your device and check whether it says "Fastboot mode" or "Odin mode". Most of the time that can be done by pressing the  key when it is just booting. In case you can't figure that one out, try to search the internet - there might even be videos on YouTube on how to do that if you're lucky.

For more information see the wiki page about Deviceinfo flash methods.

Which flash method does the device support? Flash method (fastboot/heimdall/0xffff) [fastboot]:

Depending on your selection,  may ask you to analyze a   file to get offset values required for the flash method. Get the right one for your device from TWRP, LineageOS ( inside the zip archive) or by extracting it from within a running Android. If you can't find any, you can skip this step for now by just pressing the return key.

You can analyze a known working boot.img file to automatically fill out the flasher information for your deviceinfo file. Either specify the path to an image or press return to skip this step (you can do it later with 'pmbootstrap bootimg_analyze'). Path: /home/user/Downloads/twrp-3.2.0-0-mako.img NOTE: You will be prompted for your sudo password, so we can set up a chroot to extract and analyze your boot.img file (native) install alpine-base (native) install file unpackbootimg

Interfaces
We recommend that you start with  first, because while it is not really suitable for a phone, it has a high chance of working due to that it uses X.Org which has a fbdev backend unlike most Wayland compositors which require working DRM (Direct Rendering Manager, which generally only works properly on close-to-mainline kernels). After that one works, feel free to try out another interface (but expect that it will not necessarily work out of the box). Username [user]: Available user interfaces (5): User interface [xfce4]: Build options: Parallel jobs: 3, ccache per arch: 5G Change them? (y/n) [n]: Additional packages that will be installed to rootfs. Specify them in a comma separated list (e.g.: vim,file) or "none" Extra packages [none]: Your host timezone: Europe/London Use this timezone instead of GMT? (y/n) [y]: WARNING: The applications in the chroots do not get updated automatically. Run 'pmbootstrap zap' to delete all chroots once a day before working with pmbootstrap! It only takes a few seconds, and all packages are cached. Done!
 * none: No graphical environment
 * hildon: (X11) Lightweight GTK+2 UI (optimized for single-touch touchscreens)
 * luna: (Wayland) webOS UI, ported from the LuneOS project (Not working yet)
 * plasma-mobile: (Wayland) Mobile variant of KDE Plasma, optimized for touchscreen
 * weston: (Wayland) Reference compositor (demo, not a phone interface)
 * xfce4: (X11) Lightweight GTK+2 desktop (stylus recommended)

Logging
Open a second terminal and run the following command to see detailed logging (such as compiler output). Whenever reporting that something does not work, please attach the detailed log output from this window.

Kernel package
While the goal is to use a mainline kernel for all devices in the long run, this can usually not be done in one step when porting to a new device. What we do in the meantime is shipping a Linux kernel fork, that is known to work with this device (e.g. from Android).

The steps below are the straight forward changes you need to compile your kernel. For details see the downstream kernel specific package article.

APKBUILD file
file is a script used to build a package. There are two APKBUILDs you have to edit: for device and linux packages related to your port. The APKBUILDs located at packages' folders.

Where to find device-related packages folders?

In case you cloned pmbootstrap from git: $workdir/aports/device/testing/device-wiki-example/APKBUILD $workdir/aports/device/testing/linux-wiki-example/APKBUILD

In case you have not cloned pmbootstrap from git: $workdir/cache_git/pmaports/device/testing/device-wiki-example/APKBUILD $workdir/cache_git/pmaports/device/testing/linux-wiki-example/APKBUILD

Where $workdir is the path you provided at the first step of  process and "wiki-example" by the brand and codename you provided there.

Source code
Find the source code of the known working kernel fork. Try to find a widely used kernel if possible, for example from LineageOS. The kernel version is also important, as of writing (April 2020), the lowest kernel version number we have packaged is 3.0.x. It might be possible to get even older kernels running (with old GCC versions), but even if you get them to boot, you will likely run into problems down the road.

Once you have your kernel, adjust the  section in the   file. For LineageOS kernels, you will only need to change  and   variables. Usually it makes sense to use a commit from the most recently updated branch. For example, if the kernel repo is at, you would use   and   (find the commit by clicking on c4914db2 next to "Latest commit" at the top right corner of the directories box).

If your kernel is not in a LineageOS repository but somewhere else, you also have to change the URL in  accordingly, e.g. to  if the kernel is in. You still need to set  and   as described above.

If your kernel is only available as archive (zip, tarball, etc.), you can unpack it and use  for now. Later on, when it's time to upstream your work into the official postmarketOS repositories so everybody can use it, talk to us so we can publish the kernel in a good place.

Do not fork the kernel and add patches there. There are already enough Linux kernel forks out there, and it's next to impossible to understand which kernel repository has which patches applied. Let's not make the situation worse with creating another fork with random patches on top just to make it compile with postmarketOS. Instead, point to the kernel you found. All postmarketOS specific patches should be applied as patch files in the same directory as the APKBUILD. How this is done exactly is described further below in the porting guide. When doing it like that, we avoid downloading the huge kernel sources every time a new patch is applied (remember that not everybody in the world has fast Internet connections), and it makes it much more transparent as the actual patches show up in code reviews.

Consider the reliability of the kernel source. If there is any chance that the source might disappear, a backup must be taken and used instead of the original source. See How to properly backup downstream kernels for instructions.

Kernel version
In the repository with the kernel source code, you will find a. Open this file and adjust the  in the kernel   to the information from the ,   and   variables (e.g. 3.4.0).

Defconfig
Next you will need to find the kernel configuration that is used to compile that kernel source for your device. Download it and save it as  (replace   and  ).

If your device is 64bit (aarch64) replace  with

Download sources and update checksums
Use the checksum command. It will not only generate the checksums of all source files, but also download them in case they have not been downloaded yet. If this command fails, most likely the download URL is invalid and needs to be adjusted in the  again. Another cause could be, that the defconfig could not be found (e.g. because it was saved with a wrong file name). The actual download URL (with all variables replaced) and the download progress are visible in the log window.

Kernel configuration
The magic command, which lets you change the kernel configuration is. Don't try to manually change the defconfig file, because only by running menuconfig, the dependencies will get resolved properly. always runs on the kernel with all patches applied, so we'll run it once to see if we need to remove patch files first.

If there are no errors, you can exit menuconfig with ESC-ESC and move on to making kconfig check happy.

Remove failed patches
You will find some example patches already in the generated kernel package. When a patch does not apply correctly, you will get something like the following in the log window (scroll up, the error is above the  line).

>>> linux-wiki-example: Unpacking /var/cache/distfiles/linux-wiki-example-ffff.tar.gz... >>> linux-wiki-example: 01_msm-fix-perf_trace_counters.patch patching file arch/arm/mach-msm/perf_trace_counters.h Hunk #1 succeeded at 158 (offset 37 lines). >>> linux-wiki-example: 02_this_patch_fails.patch patching file arch/arm/mach-msm/perf_trace_counters.h Hunk #1 FAILED at 121. 1 out of 1 hunk FAILED -- saving rejects to file arch/arm/mach-msm/perf_trace_counters.h.rej >>> ERROR: linux-wiki-example: all failed

When this happens, remove the failing patch from the  variable in the , and delete the patch file from the same folder. Finally, correct the checksums and try kconfig edit again.

Make kconfig check happy
Check what you need to adjust in the kernel config before it can be used with postmarketOS. Keep changing the options, until everything passes.

Kernel compilation
Next up is the kernel compilation, which will fail a few times before you get it working. Run it once to see where it fails.

We most likely use a more modern version of GCC compared to what your device kernel was intended to be compiled with (which is good, we don't want outdated software). However, this means that you will probably need to patch your kernel before it compiles successfully. Don't be scared, we'll talk you through it. But in the unlikely case that everything runs through smoothly, continue reading here.

Find the error message
To find the error message, you should open a log file in your favorite text editor, like and use search to find error messages for the last build run (they contain  or   word).

Examples of errors: In file included from arch/arm/mach-msm/perf_trace_counters.h:127:0, from arch/arm/mach-msm/perf_trace_counters.c:14: include/trace/define_trace.h:79:43: fatal error: ./perf_trace_counters.h: No such file or directory

drivers/built-in.o: In function `.LANCHOR1': msm_iommu_sec.c:(.data+0x9298): undefined reference to `kgsl_iommu_sync_lock' msm_iommu_sec.c:(.data+0x929c): undefined reference to `kgsl_iommu_sync_unlock' Makefile:877: recipe for target '.tmp_vmlinux1' failed make: *** [.tmp_vmlinux1] Error 1

It is possible to clear the log file right before compilation when you press +  in the log window and use  :

Another trick to find the error message real quick is to open  with   and use the follow mode (press  while in   or open less with the   option:  ). This causes  to behave like. When an error occurs, you can exit the follow mode by pressing +  and use  to reverse search the output (for example:  ). Press to re-enable follow mode.

From postmarketOS aports
It is highly likely that we already ran into the same issue with another kernel. Take (parts of) the offending file name and search for it inside.

When there is a result, copy the patch file you found to your new kernel package, add it to the  variable in the   and try building again.

From elsewhere
Fire up your favorite search engine and look at all results for the error message and variations of it. The  feature of most search engines is useful, so it searches for an exact string and not single words. Example queries for the error messages above:

In most cases, this will yield a patch that you can apply to your kernel. Save what you have found as a patch file right next to the  of your new kernel package. Mailing list posts are usually in the format of a patch file and can be used directly, while commits or pull requests (PRs) on GitHub can be downloaded as patch when you append  to the URL (e.g. commit, patch).

If what you found on the web can't be used as patch file directly (e.g. sometimes the files are in other folders), but you understood how you would need to patch the source (from the search results or simply because you already knew), please follow this guide.

Patch files can contain arbitrary text before the first line with  in the file. Please use this space to link to the source where you found a patch (in case it is from the Internet) and to paste the error message, that your patch fixes (so it is easier to find for other people).

After creating the patch file and adding the source URL and error message, put the file name into  in your   and give it another shot.

We can't promise anything, but you shouldn't need to do this more than 2 times or so before the kernel build finally goes through.

Removing python2 dependency
In some downstream kernels, weird python scripts are running as part of the build process. This is especially problematic for python2 scripts, as python2 has been removed in Alpine 3.16 (postmarketOS v22.06). So if your kernel build fails with an error message mentioning that "python2" was not found, here are some tips to get rid of the dependency:


 * If the python2 program is mediatek's drvgen: this is for generating a "cust.dtsi" file. Just include the the "cust.dtsi" file it would generate and don't call drvgen during the build. You can obtain the file by checking out the v21.12 branch of pmaports.git, adding your kernel package there, adding python2 to makedepends temporarily in the APKBUILD and starting the build. Once it got past the part where it would stop with the python2 error, the cust.dtsi file should be available. Create a patch that adds it and disables drvgen, search pmaports.git master for drvgen to find similar patches.
 * If the python2 program is mkdtimg (or mkdtboimg), you should be able to use the python3 version we have packaged in android-mkdtboimg instead. Use "git grep" to find similar patches, e.g..

Using GCC6
If you can't make your kernel compile or boot with the latest GCC from Alpine, you can also try to use GCC6 instead.

Using GCC4
As GCC4 was recently introduced in postmarketOS repos, you can follow the procedure for GCC6 above and replace all gcc6 occurrences with gcc4 and add gcc4 (armv7/armhf/...)-gcc4 to your list of dependencies.

Using Clang
To use Clang as compiler you have to do the following in kernel package's APKBUILD:


 * Add  to
 * Add these lines:

Device specific package
Open the  file in an editor (replace  ).

Now adjust:



If your device uses UFS storage, you may need to configure the rootfs image sector size. It defaults to 512b, but some devices use 4096b. In TWRP, check your sector size through the terminal:

If the sector sizes are 4096 bytes, add the following line to the  file:

You can read more about sector sizes on this pull request thread.

In case you were asked for  analyzing, and skipped that section during init: You can run   to get the right values for the   lines now. Filling out manually also works, but that is error-prone and therefore not recommended.

See deviceinfo reference for a listing of all available variables and their meanings. The device specific package article explains advanced customization of the.

Create checksums and build the device package once to make sure it doesn't contain errors at this point (we didn't do that earlier, because  would have complained about the invalid   of the kernel package):

We are happy to help you!
If you get stuck, we are happy to help you in the chat and in the issues tracker. When asking for help, always include the APKBUILD you have written, and any custom patches you have applied, as well as the error message you have gotten from.

Documentation
This is a wiki, so please adjust everything that isn't detailed enough or would have helped you with porting.

If you have made some progress with a new port, please create a Device page to document your findings. Even if you didn't get very far and the kernel does not compile, this will help others to continue your work. To create a device page, you will need to register an account on this wiki. (You do not need to provide an e-mail address.)

Installation
To install to the system partition of an image file, run the following:

If you want to install to a SD card, insert it into your PC and run the following. Replace mmcblk0 with the actual device name ( is handy to find out the correct device name). You don't need to format or partition it beforehand,  will take care of that.

Flashing
Before you can run any flash command, you must put your device in the flashing/bootloader mode. It is usually done holding Volume Down &amp; Power simultaneously when the device is switched off but it may vary depending on the device. For more information see the specific page for your device in the LineageOS Wiki.

If you want to install to the system partition, run the following (not for the SD card installation!):

In case your system partition is too small for the generated image (e.g. because you chose Plasma Mobile as UI), it is possible to flash to another partition as well. Just be sure to erase any previous installations of postmarketOS in other partitions, because the init script will start with the first one that it encounters. (To delete a previous version either use  or simply install the known working OS, e.g. Android, on it). Using multiple partitions with LVM is planned.

If you have a device that works with fastboot, you can boot the kernel now without flashing it:

Otherwise, you will need to flash the kernel to the device boot partition:

Alternatives to regular flashing
If the flashing method does not work, it is also possible to export all generated image files to a specific directory (with symlinks), so you can flash it manually with your host Linux system (or even on Windows with proprietary flashers such as Odin, if this is the only way it works for you):

For Android based devices, you can do a recovery zip installation.

When all else fails, you might have success with installing via netcat or booting via NFS.

USB Network
If you are lucky, your screen may give some clues that you are booted into pmOS. If not, do not get discouraged, the graphics on your device may not yet be setup correctly. The next steps are to see if you can connect to the device through SSH over USB (or if that fails, via telnet). See the Boot process and Inspecting the initramfs pages for more details.

It is quite easy to give your phone Internet access via USB when your PC is connected to the Internet.

In case it looks like your device did not even boot, have a look at Troubleshooting:boot.

Upstreaming
As soon as USB networking is functional, or you have another indication that booting the device works successfully, it is time to upstream your work into the official pmaports repository. This way other people can benefit from your work, and build upon it.

See the git workflow article for detailed instructions.

To get notified of work affecting your device, we recommend adding yourself to the GitLab CODEOWNERS files in pmaports, use the following format as an example:

device/*/device-oneplus-enchilada/		@calebccff device/*/device-oneplus-fajita/			@calebccff device/*/firmware-oneplus-sdm845/		@calebccff device/*/linux-postmarketos-qcom-sdm845/	@sdm845-mainline

Display
To make the display work in the first place, read Troubleshooting:display and Tuning sysfs.

After you have it working, please take some nice photos and add them to your device's wiki page. If you have a Reddit account, consider posting them in /r/postmarketOS as well.

Touchscreen
To get it working, visit the screen calibration page. If you're having trouble, visit touchscreen troubleshooting.

Install packages over SSH
Get Internet access via USB (easier) or Wifi, then use the package manager to install new packages:

You can also host packages you have built yourself from your PC. Just make sure to increase the package version when you build your own version of a package that already exists. Otherwise the package manager can not know that your package is the newest one and should be installed. Check the output of  to see whether it is really installing the package or not.

Building a new system image
Whenever you rebuild a package (or pick a new one to be installed by default in ), you need to make sure that the package is actually installed in the chroot from which the system image gets generated. Achieve that by running  again, it should update all outdated packages. Pay attention to the output of  to see if it actually has been updated. If something did not work as expected, you can always  your chroots to start over with a clean installation.

Kernel
A simple way to recompile your kernel (e.g. because you want to change your kernel config) and flash it to your device is running the following commands:

The last flash_kernel step is only needed if your device has the kernel stored on an extra boot partition. Android/fastboot compatible devices have such a partition, and Maemo/MeeGo Nokia devices (N900, etc.) typically don't use it. If your device does not have a boot partition, update your system partition or SD card.

After you've gotten more familiar with postmarketOS, you could try out the  as well. It allows you to flash a new kernel to the device's  partition (not to be confused with postmarketOS' own boot subpartition  ).

Full disk encryption: osk-sdl support
If the display and the touchscreen interface are working, then it's time to add support for  so that you are able to use full disk encryption on the root filesystem. Instructions for adding support can be found here: Porting osk-sdl to New Devices

Advanced topics

 * Interfaces
 * WiFi
 * Bluetooth
 * Audio
 * Modem
 * Sensors
 * Mainline kernel
 * Existing Alpine installation
 * Hybris