Porting to a new device

From postmarketOS Wiki

Introduction

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

Note Beginner speaks to beginners: Have a look at the summary to keep the whole process in mind!

The main steps are:

  • Set up a 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:

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

Note Please use a spare device for experimenting with postmarketOS! You won't be able to use typical phone features right now, such as making calls, sending text messages, or using Bluetooth. Although everything has been tested, there is no guarantee that you won't break your device.
  • 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 getrandom 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 (#1203) and the Vodafone 858 Smart from 2011 (#1592)). 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: 

$ pmbootstrap init
Location of the 'work' path. Multiple chroots (native, device arch, device rootfs) will be created in there.
Work path [/home/user/.local/var/pmbootstrap]:

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 fastboot, some Samsung models need heimdall (which is compatible to "Odin") and Maemo/MeeGo-based Nokia phones work with 0xffff. 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 Volume Down 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, pmbootstrap may ask you to analyze a boot.img file to get offset values required for the flash method. Get the right one for your device from TWRP (twrp-*.img), LineageOS (boot.img 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

Note Don't choose Plasma Mobile, Phosh or Sway if you're using a downstream kernel for porting.

We recommend that you start with xfce4 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):
* 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)
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!

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. 

$ pmbootstrap log

Kernel package

While the goal is to use a mainline kernel for all devices in the long run, this usually cannot 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).

Note If your device does not have a known working Linux kernel fork around (e.g. because it is an iPhone or Windows Phone) this guide won't work straightforward. Have a look at how similar devices to yours got ported, build a generic kernel or ask in the chat for help.

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

APKBUILD file

Note APKBUILD has nothing to do with Android's app format!

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

Where can I 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 pmbootstrap init process and "wiki-example" by the brand and codename you provided there.

If you are curious about APKBUILD variables and functions, you can look at pmbootstrap specific APKBUILD options and Alpine APKBUILD Reference.


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 # Source section in the linux-wiki-example/APKBUILD file. For LineageOS kernels, you will only need to change _repository and _commit variables. Usually it makes sense to use a commit from the most recently updated branch. For example, if the kernel repo is at https://github.com/LineageOS/android_kernel_motorola_ghost.git, you would use _repository="android_kernel_motorola_ghost" and _commit="c4914db2f65ef63548b0af5d7b37d131581c9c62" (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 source accordingly, e.g. to https://github.com/jmrohwer/$_repository/archive/$_commit.tar.gz if the kernel is in https://github.com/jmrohwer/TF101-GNU-kernel. You still need to set _repository and _commit as described above.

If your kernel is only available as archive (zip, tarball, etc.), you can unpack it and use pmbootstrap build linux-wiki-example --src=/path/to/extracted/kernel/source 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. 

_flavor="wiki-example" # be sure it's in form of <vendor-codename>, e.g. motorola-ghost

# Source
_repository="(CHANGEME!)" # e.g. android_kernel_motorola_ghost
_commit="ffffffffffffffffffffffffffffffffffffffff" # e.g. c4914db2f65ef63548b0af5d7b37d131581c9c62
_config="config-$_flavor.$arch"
source="
    $pkgname-$_commit.tar.gz::https://github.com/LineageOS/$_repository/archive/$_commit.tar.gz
    $_config
    gcc7-give-up-on-ilog2-const-optimizations.patch
    gcc8-fix-put-user.patch
"
builddir="$srcdir/$_repository-$_commit"

Kernel version

In the repository with the kernel source code, you will find a Makefile. Open this file and adjust the pkgver in the kernel APKBUILD to the information from the VERSION, PATCHLEVEL and SUBLEVEL 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 aports/device/testing/linux-wiki-example/config-wiki-example.armhf (replace wiki-example and armhf). 

$ wget https://github.com/LineageOS/lge-kernel-mako/raw/cm-14.1/arch/arm/configs/lineageos_mako_defconfig
$ mv lineageos_mako_defconfig aports/device/testing/linux-wiki-example/config-wiki-example.armhf

If your device is 64-bit capable(aarch64) replace .armhf with .aarch64

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 APKBUILD 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. 

$ pmbootstrap checksum linux-wiki-example

Kernel configuration

Note If pmbootstrap throws an error here, you need to remove the example patch!

The magic command, which lets you change the kernel configuration is pmbootstrap kconfig edit. Don't try to manually change the defconfig file, because only by running menuconfig, the dependencies will get resolved properly. menuconfig 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). 

$ pmbootstrap kconfig edit linux-wiki-example

>>> 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 source= variable in the APKBUILD, and delete the patch file from the same folder. Finally, correct the checksums and try kconfig edit again. 

$ nano aports/device/testing/linux-wiki-example/APKBUILD # remove from source
$ rm aports/device/testing/linux-wiki-example/02_this_patch_fails.patch
$ pmbootstrap checksum linux-wiki-example
$ pmbootstrap kconfig edit

Make kconfig check happy

Note Consider using kconfig edit -x to get a GUI instead of the terminal interface. Details: pmbootstrap kconfig edit -h

Check what you need to adjust in the kernel config before it can be used with postmarketOS: search for device name in pmbootstrap log to inspect what configuration is missing or wrong. Incorrect options need to be changed if the line contains your device name. They are displayed as warnings, not as errors.

Keep changing the options until everything passes. On TUI kernel configuration interface, you can type / to search for the missing or wrong configuration and observe a matching Symbol name and its Location path. 

$ pmbootstrap kconfig check
$ pmbootstrap kconfig edit
$ pmbootstrap kconfig check

If you failed to launch pmbootstrap kconfig edit with Install ncurses (ncurses-devel) and try again. message, save the following patch as fix-check-lxdialog.patch in your kernel package directory ex. device/testing/linux-wiki-example and add it to source in your APKBUILD: 

diff --git a/scripts/kconfig/Makefile b/scripts/kconfig/Makefile
index 844bc9da..911c6ba1 100644
--- a/scripts/kconfig/Makefile
+++ b/scripts/kconfig/Makefile
@@ -192,6 +192,8 @@ clean-files	+= zconf.tab.c zconf.lex.c zconf.hash.c gconf.glade.h
 clean-files     += mconf qconf gconf nconf
 clean-files     += config.pot linux.pot
 
+HOSTLOADLIBES_mconf   = $(shell $(CONFIG_SHELL) $(check-lxdialog) -ldflags $(HOSTCC))
+
 # Check that we have the required ncurses stuff installed for lxdialog (menuconfig)
 PHONY += $(obj)/dochecklxdialog
 $(addprefix $(obj)/,$(lxdialog)): $(obj)/dochecklxdialog
@@ -217,8 +219,6 @@ HOSTLOADLIBES_gconf	= `pkg-config --libs gtk+-2.0 gmodule-2.0 libglade-2.0`
 HOSTCFLAGS_gconf.o	= `pkg-config --cflags gtk+-2.0 gmodule-2.0 libglade-2.0` \
                           -Wno-missing-prototypes
 
-HOSTLOADLIBES_mconf   = $(shell $(CONFIG_SHELL) $(check-lxdialog) -ldflags $(HOSTCC))
-
 HOSTLOADLIBES_nconf	= $(shell \
 				pkg-config --libs menu panel ncurses 2>/dev/null \
 				|| echo "-lmenu -lpanel -lncurses"  )
diff --git a/scripts/kconfig/lxdialog/check-lxdialog.sh b/scripts/kconfig/lxdialog/check-lxdialog.sh
index 9d2a4c58..364eaecb 100644
--- a/scripts/kconfig/lxdialog/check-lxdialog.sh
+++ b/scripts/kconfig/lxdialog/check-lxdialog.sh
@@ -43,7 +43,7 @@ trap "rm -f $tmp" 0 1 2 3 15
 check() {
         $cc -x c - -o $tmp 2>/dev/null <<'EOF'
 #include CURSES_LOC
-main() {}
+int main() { return 0; }
 EOF
 	if [ $? != 0 ]; then
 	    echo " *** Unable to find the ncurses libraries or the"       1>&2

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. 

$ pmbootstrap build linux-wiki-example

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

Note Tip: you can use pmbootstrap log to check the log quickly.

To find the error message, you should open a log file in your favorite text editor, like 

$ nano $(pmbootstrap config work)/log.txt

and use search to find error messages for the last build run (they contain error: or Error 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 ctrl + c in the log window and use log -c: 

(old log output here)
^C
$ pmbootstrap log -c

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

Get a patch

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 aports/device. 

$ grep -r 'perf_trace_counters\.c' aports/device/
aports/device/testing/linux-lg-mako/01_msm-fix-perf_trace_counters.patch:In-tree compilation for arch/arm/mach-msm/perf_trace_counters.c was
aports/device/testing/linux-lg-mako/01_msm-fix-perf_trace_counters.patch:                     from arch/arm/mach-msm/perf_trace_counters.c:14
$ grep -r 'msm_iommu_sec' aports/device/
aports/device/testing/linux-lg-mako/02_gpu-msm-fix-gcc5-compile.patch:msm_iommu_sec.c:(.data+0x9298): undefined reference to `kgsl_iommu_sync_lock'
aports/device/testing/linux-lg-mako/02_gpu-msm-fix-gcc5-compile.patch:msm_iommu_sec.c:(.data+0x929c): undefined reference to `kgsl_iommu_sync_unlock'

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

$ cp aports/device/testing/linux-lg-mako/01_msm-fix-perf_trace_counters.patch aports/device/testing/linux-wiki-example/
$ nano aports/device/testing/linux-wiki-example/APKBUILD # add it to source
$ pmbootstrap checksum linux-wiki-example
$ pmbootstrap build linux-wiki-example

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:

  • include/trace/define_trace.h: fatal error: ./perf_trace_counters.h: "No such file or directory"
  • linux "./perf_trace_counters.h: No such file or directory"
  • android "undefined reference to `kgsl_iommu_sync_unlock'"

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 APKBUILD 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 .patch 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 source in your APKBUILD and give it another shot. 

$ nano aports/device/testing/linux-wiki-example/03_description-here.patch
$ nano aports/device/testing/linux-wiki-example/APKBUILD
$ pmbootstrap checksum linux-wiki-example
$ pmbootstrap build linux-wiki-example

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 -add it to makedepends- we have packaged in android-tools "android-mkdtboimg previously" instead. Use "git grep" to find similar patches, e.g. device/unmaintained/linux-xiaomi-cepheus-downstream/0005-Use-real-mkdtimg-don-t-use-python2-one.patch.

Changing compiler

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 clang to makedepends
  • Add these lines:
export CC="clang"
export HOSTCC="clang"

Example

Device specific package

Note If your device has a boot partition smaller than ~16MB, or if flashing the kernel fails with an "image too large" error, you might need to switch to the minimal initramfs.

To do so, open the APKBUILD file in an editor (replace wiki-example). 

$ nano aports/device/testing/device-wiki-example/APKBUILD
Find the line that starts with depends and add postmarketos-initramfs-minimal to it.

Open the deviceinfo file in an editor (replace wiki-example). 

$ nano aports/device/testing/device-wiki-example/deviceinfo
Note In case you were asked for boot.img analyzing, and skipped that section during init: You can run pmbootstrap bootimg_analyze path/to/boot.img to get the right values for the deviceinfo_flash_offset_ lines now. Filling out manually also works, but that is error-prone and therefore not recommended.

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 a root shell, check your sector size with: 

# blockdev --getss /dev/block/sda

If the sector size is 4096 bytes, add the following line to the deviceinfo file:

deviceinfo_rootfs_image_sector_size="4096"

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

If deviceinfo_header_version is 2 or higher, fill in deviceinfo_dtb with your device's dtb. This can be found in your kernel source under /arch/{your device's arch}/boot/dts/{your device's SOC brand}/. It may take some trial and error to figure out which .dts file is used. If in doubt, choose the one with the name of your SOC or the name of your device.

Thus, in deviceinfo_dtb, put {your device's SOC brand}/{the name of your device's .dts file, not including the file extension}. See Device Tree (dtb) for more information.

Note Older devices (generally 2014 and earlier, and pretty much anything armv7) do not use DTBs, and instead use board files (you can find them in arch/arm/mach-(manufacturer) or in rarer cases, in arch/arm/plat-(manufacturer)). In those cases, you can skip the deviceinfo_dtb variable.

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

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 pmbootstrap would have complained about the invalid pkgver of the kernel package): 

$ pmbootstrap checksum device-wiki-example
$ pmbootstrap build device-wiki-example
Note If you are getting a dtb files not found error, that may be because you used the model number of the device instead of the code name, see issue #35. To fix the problem, look at renaming the port, or simply create a new port with the correct name.
Notice If your device requires executing udev rules early in boot (initramfs), they must be added to the initramfs configuration

This can be done in the device package by creating a file that lists the rules: 

# 10-device-initramfs-extra.files
/usr/lib/udev/rules.d/device-specific.rules

And installing this file in the device package APKBUILD: 


install() {
...

	install -Dm644 "$srcdir"/10-device-initramfs-extra.files \
		-t "$pkgdir"/usr/share/mkinitfs/files-extra/

...
}

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 pmbootstrap log.

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

Note If you get a "no space left on device" error, please report in #928.
Notice With !2426 pmboostrap moved to using GPT as a default parititon table, if the device does not support GPT (e.g. legacy u-boot), then add 
deviceinfo_partition_table="msdos"
to the deviceinfo file.

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

$ pmbootstrap install

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 (lsblk is handy to find out the correct device name). You don't need to format or partition it beforehand, pmbootstrap will take care of that. 

$ pmbootstrap install --sdcard=/dev/mmcblk0

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 & 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!): 

$ pmbootstrap flasher flash_rootfs

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 dd or simply install the known working OS, e.g. Android, on it). Using multiple partitions with LVM is planned (#60). 

$ pmbootstrap flasher flash_rootfs --partition userdata

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

$ pmbootstrap flasher boot

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

$ pmbootstrap flasher flash_kernel

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): 

$ pmbootstrap export
$ pmbootstrap export --odin

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 Lemmy account, consider posting them to [1] as well.

Touchscreen

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

Changing your installation

Install packages over SSH

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

$ apk add hello-world

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 apk 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 pmbootstrap init), 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 pmbootstrap install again, it should update all outdated packages. Pay attention to the output of pmbootstrap log to see if it actually has been updated. If something did not work as expected, you can always pmbootstrap zap 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: 

$ pmbootstrap build --force linux-wiki-example
$ pmbootstrap install
$ pmbootstrap flasher flash_kernel

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 postmarketos-update-kernel as well. It allows you to flash a new kernel to the device's boot partition (not to be confused with postmarketOS' own boot subpartition systemp1).

Full disk encryption support

The default application for users to unlock full disk encryption at boot is Unl0kr, some additional steps may be required to support this application on your device. Please refer to the Unl0kr wiki page for info on debugging/troubleshooting it.

Advanced topics

Note Out of ideas what to do next with postmarketOS? Check out the get involved section from the last big blog post!
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