Linux kernel driver for the Broadcom 2708 PWM peripheral, for use with WS2812 LED strips by Bart Coppens.

This project was inspired by https://github.com/jgarff/rpi_ws281x which does roughly the same, but all in userspace. I didn't like the
idea of userspace doing DMA and driving my peripherals without the kernel's knowledge, and this was a nice reason to write a kernel
driver and experiment with it.

Tested on my Raspberry Pi B+ with an Adafruit NeoPixel Ring with 16 WS2812 LEDs.

Directory structure:
* linux/ Linux kernel module, and the required (small) kernel patch for kernel 3.16.5
* lib/ Code to access the kernel module's character device
* apps/ Test example using the code in lib/ to drive a NeoPixel ring:
  - ws2812_bcm2708_demo: a very simple demo that does some animations with color transitions
  - clock: a simple clock app
  - stress: a stress test for the irq

Build instructions:
* Build a patched 3.16.5 kernel
* build the kernel module:
  cd pwm-bcm2708/linux
  ARCH=arm CROSS_COMPILE=${CCPREFIX} KERNELDIR=${KERNEL_SRC}/ make
  where CCPREFIX is /path/to/crosscompiler/arm-unknown-linux-gnueabi-
* Build the libs and demo app:
  cd pwm-bcm2708/
  mkdir build ; cd build
  CC=arm-unknown-linux-gnueabi-gcc CXX=arm-unknown-linux-gnueabi-g++ cmake .. && make
* Copy the files over to your Pi
  insmod pwm-bcm2708.ko
  mknod dev_pwm c `grep pwm /proc/devices | cut '-d ' -f1` 0
  build/apps/ws2812_bcm2708_demo dev_test

Sources:
* https://github.com/jgarff/rpi_ws281x
* https://github.com/hermanhermitage/videocoreiv/wiki