mfrc522-linux

Linux driver for the MFRC522 chip, written in C and Rust

General instructions

Remember to clone the submodules as well. This can be done by using one of the following commands:

• git clone --recursive https://github.com/ks0n/mfrc522-linux
• Cloning the project and running git submodule update --init

Module Features

sudo insmod mfrc522.ko

A few commands are available:

Command	Arguments	Example	Description
mem_read	None	mem_read	Read the internal memory of the MFRC522 to the driver's internal buffer. Access the content of this buffer by reading the device, e.g cat /dev/mfrc522_misc
mem_write	[Length of the data]:[Extra]	mem_write:4:mfrc	Write to the internal memory of the MFRC522
get_version	None	get_version	Display the MFRC522's hardware version (v1 or v2)
gen_rand_id	None	gen_rand_id	Generate a 10-byte-wide random number and store it in the MFRC522's internal memory. Use mem_read to read it
debug	[Mode (On/Off)]	debug:on	Enable debug information upon MFRC522 memory writes or reads(Only available in the C module)

You can also fetch statistics via the sysfs about the driver's amount of read and written bits (Only available in the C module).

C module

Setup

If you don't have a cross compilation toolchain, run activate.sh to download an arm toolchain. If you already have one, don't forget to set ARCH and CROSS_COMPILE environment variables. Remember to source toolchain.env to set the different environment variables expected by the kernel

Compiling the Raspberry kernel

This project was developed using the Raspberry fork of linux, but also works with the mainline kernel in 64 bits.

cd linux/
make bcm2709_defconfig
make

You will need to tweak the DTS in order for the Raspberry Pi to associate the MFRC522 with our driver. A basic example is provided in the root of the repository, named bcm2710-rpi-3-b-plus_mfrc522.dts. You can compile it and use it on your Pi as is, by replacing it in /boot/bcm2710-rpi-3-b-plus.dtb.

Follow Raspberry's guide to flash your newly compiled kernel onto your SD Card.

Compiling the driver

cd module/
make

This will produce a file named mfrc522.ko. Copy this file to your Raspberry Pi.

Rust module

Welcome to the crab zone

Setup

Make sure that llvm and clang are at least in version 10.0.1.

Follow this quickstart guide to get started on compiling a kernel with Rust support.

Remember to use the provided rust_kernel_config provided at the root of the repository.

Compiling the ks0n kernel

cp rust_kernel_config linux-next/.config
cd linux-next
make LLVM=1 LLVM_IAS=1 ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu-

Be careful, the ethernet card will be disabled but Wifi will be working.

Since we are using LLVM, no need to download a cross compiling toolchain. We are also compiling a 64 bit kernel, so be careful of that.

You will need to tweak the DTS in order for the Raspberry Pi to associate the MFRC522 with our driver. A basic example is provided in the root of the repository, named bcm2710-rpi-3-b-plus_mfrc522_aarch64.dts. You can compile it and use it on your Pi as is, by replacing it in /boot/bcm2710-rpi-3-b-plus.dtb.

Follow Raspberry's guide to flash your newly compiled kernel onto your SD Card.

Compiling the driver

cd rust-module/
make LLVM=1 LLVM_IAS=1 ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu-

This will produce a file named mfrc522.ko. Copy this file to your Raspberry Pi.

Known issues

The rust driver has a non-deterministic rate of success. It will sometimes explode right after SPI initialization, and sometimes only upon the module's deletion. We are currently working on bringing an abstraction for the SPI part of the Kernel into the rust-for-linux kernel, and development is quite hard and imprevisible. While the module does not always work, we are close to completing it, and almost all C features are implemented!