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https://github.com/ddvk/remarkable2-framebuffer

remarkable2 framebuffer reversing
https://github.com/ddvk/remarkable2-framebuffer

Last synced: 3 months ago
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remarkable2 framebuffer reversing

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README 

        
## remarkable2-framebuffer



This repo contains code for drawing to the rM2's framebuffer.



## Status



quality: beta



rm2fb can open the framebuffer and draw to it. rm2fb-server exposes a simple

API for other processes to draw to the framebuffer using shared mem and message

queues. rm2fb-client is a shim that creates a fake framebuffer device for apps

to use, allowing rM1 apps to seamlessly draw to the display of the rM2.



## Installation



Before installing, be sure that your xochitl version is supported: https://github.com/ddvk/remarkable2-framebuffer/blob/master/src/shared/config.cpp.



rm2fb is available as a package in [toltec](https://github.com/toltec-dev/toltec) which

sets up the server and client parts for you. Otherwise, the instructions below can be used

for manual installation.



## Set up build environment



[set up remarkable toolchain](https://remarkable.guide/devel/toolchains.html)



## Building



Source the remarkable toolchain (example below) and run the following (replacing ${GITROOT} with the directory you have checked the repository out to)



```

source /usr/local/oecore-x86_64/environment-setup-cortexa9hf-neon-oe-linux-gnueabi

cd ${GITROOT}

qmake

make

```



### Framebuffer Server



build `src/server/librm2fb_server.so.1.0.1`.  Copy it to your

remarkable and run:



```

LD_PRELOAD=/path/to/librm2fb_server.so.1.0.1 /usr/bin/xochitl

```



### Framebuffer Client Shim



build `src/client/librm2fb_client.so.1.0.1`.  Copy it to your

remarkable and run: `LD_PRELOAD=/path/to/librm2fb_client.so.1.0.1 ` to

run your app.



The client intercepts interactions with `/dev/fb0` and forwards them to the

rm2fb server.



## Configuration



To do their job, both the client and the server need to know the address at which a number of functions reside in the Xochitl binary.

These addresses change from one release to the next.



Xochitl function name | Xochitl function role | Notes

--------------|---------------|----------

`update` | Sends an update request. This function is replaced by the client shim to talk to our server instead. | Uses the string `Unable to complete update: invalid waveform (`. Prior to version 2.9, the signature of this function was `void (*)(void*, int, int, int, int, int, int)`. Starting from version 2.9, it changed to `void (*)(void*, QRect&, int, int)`.

`create` | Start the threads that handle update requests. This function is replaced by the client shim with a no-op to avoid conflicting with the server. | Uses the string `Unable to start generator thread\n`.

`wait` | Waits until the update-handling threads have started. This function is replaced by the client shim with a no-op to avoid conflicting with the server. | Calls `usleep(1000)`.

`shutdown` | Stops the update-handling threads. This function is replaced by the client shim with a no-op to avoid conflicting with the server. | Uses the string `Shutting down...`.

`getInstance` | Retrieves the instance of the singleton SWTCON class. This function is used by the server to interact with the screen. | Calls a function that itself calls `create` and `wait`.

`notify` | Called when the framebuffer has been updated, used for the Qt signal/slot connections needed for ScreenShare to work | 



The client and the server both ship the [hardcoded addresses](https://github.com/ddvk/remarkable2-framebuffer/blob/master/src/shared/config.cpp#L13) for these functions for various releases.

If you get a message saying `Missing address for function […]`, it means that the release you’re running is not yet supported. Please report this in [this dedicated thread](https://github.com/ddvk/remarkable2-framebuffer/issues/18).



You can manually locate the addresses of the functions listed above by [looking at the disassembly and then add a configuration entry to make remarkable2-framebuffer work with your release](tutorial).

In addition to the hardcoded configuration entries, the client and the server will look for addresses in configuration files in the following locations:



* `/usr/share/rm2fb.conf`

* `/opt/share/rm2fb.conf`

* `/etc/rm2fb.conf`

* `/opt/etc/rm2fb.conf` (best option for Toltec users)

* `rm2fb.conf` (relative to the current working directory, best option for manual installs)



## [Demo](https://imgur.com/gallery/zGMn7Qs)



## Contributing



Please look at the open github issues and add a new one for any work you are planning

on doing so people can see ongoing progress.



Things that can use help:



* writing documentation

* testing apps and packages

* understanding the waveforms used by SWTCON

* writing our own implementation of SWTCON

* adding support for new OS releases



## FAQ



* will this brick my rM2?



probably not, but no guarantees



* [what apps are supported?](https://github.com/ddvk/remarkable2-framebuffer/issues/14)



* [how does rm2fb work?](https://github.com/ddvk/remarkable2-framebuffer/issues/5#issuecomment-718948222)



* [how do I port my existing app to rM2?](https://github.com/ddvk/remarkable2-framebuffer/issues/13)



* [what's up with server/client API?](https://github.com/ddvk/remarkable2-framebuffer/issues/4)



* [where can i find more information on the framebuffer?](https://web.archive.org/web/20230619082431/https://remarkablewiki.com/tech/rm2_framebuffer)



* [what about implementing an open source SWTCON?](https://github.com/timower/rM2-stuff/)



* how can I get in touch?



use github issues or ping on the discord in one of the homebrew developer

channels. if you mention this repo, someone will probably respond