FP3 : Fairphone Open OS?

ok awesome thank you. I’ll read it through before trying it out (RTFabulousM) :slight_smile: and again, thank you for your time and the info, much appreciated, :kudos: to you :bookmark:


Just to be safe, looking at this topic’s category:
Please be aware that LineageOS isn’t available on the Fairphone 3 yet, even a custom recovery program with which to install it isn’t available yet.

Everything we might say right now and here in this regard is just how LineageOS works in practice on the Fairphone 2 (where it works awesome).


OK thanks for the info :+1: I’m happy with Android for now but am just asking out of curiosity.

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LineageOS is Android, too :wink: .
Android is just the base for all vendor-specific or community-specific adaptations, see https://en.wikipedia.org/wiki/Android_(operating_system)#AOSP.


yes I know :slight_smile: I just meant Google Android vs Foss OS but good point :+1:

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I pre-ordered my FP3 when I read on the fairphone site that they want to bring out an open OS for FP3, too. Got my FP3 finally in the beginning of November. Since then I am waiting for the open OS. I feel a bit cheated now to hear there will be no FP3 OS.
I’m no dev, so I can’t support working forward to an open OS for FP3.
But there are some articles concerning open source licencing in the present c’t (german IT journal). They say if the Android Open Source Project is based on GPL and FP3 OS is based on Android FP3 OS kernel sources must be released for FP3 customers.

I think this might address your point :slight_smile: :

And welcome to the Fairphone Community! :+1:


I moved your post here because you refer to Fairphone Open OS.
This would not be LineageOS, which is a community effort aside from official smartphone vendor OSes.

The site says for a while now
“We are currently investigating the possibility of making Fairphone Open available on Fairphone 3.”

Where do you “hear” that there definitively will be no Fairphone Open OS on the Fairphone 3?


Thanks a lot for the detailed and interesting post! I was wondering if you can give some pointers to books/tutorials/any other information that you’ve used to obtain this kind of knowledge?
I’m a developer myself so i’m not afraid of code, but i’ve never tried anything close to porting android (or linux) to a device. I know there is a lot of information to be found on https://www.xda-developers.com/, but it would be great if you know about a good book or other place to start getting into this stuff…

I came across this kind of info during my previous job a few years ago. We first used a standard Raspberry Pi as a platform for an embedded Linux running device and were upgrading to a newer system-on-a-module platform that had linux support. However we ended up soldering that module on our own custom motherboard, which had a lot of periphery on pins different to the arrangement on the reference developer board that came with that system-on-a-module.

(manufacturers regularly sell those so potential customers can try out a module/chip before committing to buying a million of them - the reference boards usually have all sorts of periphery to showcase all the features of the CPU/module, often most aren’t needed for a specific application, and most embedded CPUs have their pins soft-wired and configurable - meaning the very same solder pad/pin can be USB, serial IO, a GPIO, I2C, connected to an sdcard, etc… and the bootloader needs to first configure the chip correctly to address whatever hardware is actually connected to it.)

I then had the problem of modifying the Linux image that the module manufacturer provided to work with our own hardware (similar to what Fairphone likely had to do with the reference image they certainly got from Qualcomm)

On X86 Linux doesn’t need to deal with any of that. The BIOS/ACPI framework (and it’s EFI successors) do it for you, and on X86, hardware can usually be addressed through known IO port addresses. (remember 0x3f8 for serial port? :wink: )

On ARM, which is much more configurable, and there’s actually CPU instructions to change what pin does what, Linux relies on the device tree framework to tell it which hardware is connected to which pin, and how that pin needs to be configured to work (and not fry that hardware or the CPU)

This sheds a bit of light on the topic:

Android so far uses a Linux kernel, and as such getting a self built android kernel to run on a phone (or any other ARM embedded platform) is no different from getting any custom linux to run. You need to tell it where it can find which hardware, and put all other pins into a safe state that won’t burn anything.

The latter is especially important when GPIOs (general purpose input output) pins are connected to high power Transistors that control current flow to and from components such as batteries, control FANs (you don’t want to overheat something) or are unused and hardwired to ground (in which case you don’t want to configure the pin to become a “driven”, active low output, because then it would try to apply voltage to a pin thats wired to ground, which causes a short inside the CPU. Not all embedded CPU’s tolerate that. (The datasheet of the CPU can tell you, it can usually be downloaded from the manufacturer, usually for free and public, but some idiotic manufacturers require to sign an NDA or even pay for that information)
A similar issue happens if the pin remains unconnected (open) but is configured as an “input” - because then its floating and can trigger IRQs and/or make things unstable.

A good board manufacturer will design a board such that all pins in their default (@bootup and uninitialized) configuration is safe, and most CPU’s will configure the pins in as benign a configuration as possible (input, active high with or without a high Ohm pulldown to prevent them from floating) but unfortunately you can’t rely on
that to be always the case.

Effectively, to be able to write the device tree from scratch, you’d need the data sheet and reference documentation from Qualcomm, and the circuit/connection diagram from Fairphone, which tells you what periphery is connected to which pin on the Snapdragon processor.

If you don’t have the circuit diagram, you can try to reverse-engineer it, by opening the phone (which luckily isn’t that hard) and figuring out which pin of the CPU is connected to what other component (as well as identifying these components and what the pins there do) - taking the data sheets for all these chips as reference - usually downloadable on the manufacturers webpage.

OR, since Fairphone has released the kernel source code, which includes device tree files, one can try to read out the information from there. I tried that but failed, because I couldn’t figure out which device tree configuration is actaully loaded on FP3

Is Fairphone’s circuit plan available?

More info: https://blog.modest-destiny.com/posts/linux-device-tree-pinctrl-tutorial/

I tried to find technical manuals for the Snapdragon CPUs, but it seems like Qualcomm is only giving those to OEMs signing an NDA. source

However I found documents for the Snapdragon 410e as well as 600 which can tell you what this documentation would look like, if it was available :wink: (will of course not be valid for the FP3s 632

Edit: I should add, (after reading them) these are technical data sheets about the whole family of chips. As such they describe general information (number of UARTs, device addresses, boot modes , power specs, in case of the 410e even programming examples) but they don’t tell you which pin is where on the CPU/MPU. The reason is that each MPU architecture is usually sold in different “packages” - aka different sizes of the chip with slight change in number of available pins, amount of internal memory, etc… it’s the same core architecture but differs in “options”
so you also need the manual for the specific version used on the FP3 (and I don’t even know which one that is, though the fineprint on the chip should usually tell - it should have series/family, model, hardware revision, and possibly serial number)

Edit again: Doesn’t apply here, actually there is Pad/PIN documentation in both, it’s just formatted badly :wink:

one problem (which becomes already apparent from the 600 technical manual linked above which has a lot of sections that say “will be included in future revision of this document”) the hardware life cycles in mobile technology have become so short and the chips so complex, that the manufacturers don’t even bother writing complete documentation anymore.

instead the code (hardware description language used to design the chip) and the driver code developed alongside it become the documentation.

so, worse comes worse, even if you sign an NDA with Qualcomm, the sourcecode that Fairphone has already published (although lacking instructions/docu) might actually all you’d ever get.

scary, isn’t it? :wink:

Edit: Found another one, for Snapdragon 820e - this one has specific pin/GPIO/pad information :slight_smile:


You should get in touch with @Leo_TheCrafter who was designing a new motherboard for the FP2. You two would make an awesome team!

I was doing embedded Linux on FPGA-based Zynq systems (PetaLinux, Yocto-based) but never wanted to go down to DTS level because I was lazy to get into its complex syntax (we kept the demo boards :slight_smile:).


DTS syntax is actually quite easy. The problem is that writing a device tree is tedious: every component/driver expects different parameters and the values usually come from hardware manuals that we don’t have access to. Get one param slightly wrong and the results are unpredictable, anywhere from a component not initialising to the whole device not booting. It’s generally only feasible to derive the required values from existing FP-released DTS or DTB files.


Oh, I never wrote them from scratch, all I ever did was some edits (swapping pins, disabling unneeded components to make more GPIOs available, and I did have the CPU module datasheet and pinout, which for the Qualcomm we don’t seem to have)

Editing them is much easier than writing them from scratch!


I read through half of the thread -which was interesting- until I realized I had only come here to say this: I want a google free OS for my FP3. I don’t expect anyone to provide it. I’d just be very happy and not so half-happy anymore because I couldn’t wait and bought it already. And now I’m sitting here, watching Edward Snowden chatting with Joe Rogan, thinking: Sh***, now they know!
Happy coding!


In the meantime, while we wait for success on the open OS front, you could do what is possible already …


Although I’m not sure about this point, I would disagree here.

Additionally, I’d prefer the termFree Software“. ”Open source“ just means ”there’s some source code the progam or application uses which you can look at“.

There are already a couple of alternative OS, but I only found those for #FP2. #oslist


Did you get a reply meanwhile?

Fairphone made the source code available some time ago, there are several worthwile topics based on this already, among them …

TWRP for the Fairphone 3:

Installing Generic System Images (GSI), which are custom ROMs using Project Treble to supposedly be compatible with any Project Treble phone, such as the Fairphone 3:

The developer topic about getting something out of the source code:

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I believe the only fully free OS out of those bunch is Replicant. It has no non-free firmware blobs which im pretty sure is damn near impossible on FP3 due to qualcomm drivers etc