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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 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

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 <rm1app> 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 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.

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. 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

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

use github issues or ping on the discord in one of the homebrew developer channels. if you mention this repo, someone will probably respond