Porting a 2.4.20 character driver for legacy hardware to 2.6.15

This tutorial provides hands on experience and example for the porting of legacy character, IOCTL centric character driver to the modern Linux kernel using sysfs instead of IOCTLs as required by the community for upstream kernel acceptance. This tutorial is derived from my experience porting a simple 2.4.20 kernel IOCTL centric character driver for some legacy hardware and getting it into the 2.6.15 kernel, the tlclk driver. There were enough lessons learned that I came away thinking “this would have been a lot easer if tutorial and or sample existed for my class of hardware”. There will be no device hardware needed for this tutorial; the participants will implement a character driver module that is a full sysfs, udev citizen. This tutorial is targeted at novices that have minimal driver experience with IOCTL based character drivers on older Linux kernels, and want a hand moving their work to the current 2.6.15 or 2.6.16 kernel. Tips, advice and commentary for IHV’s moving driver support from legacy IOCTL’s to the “sysfs / udev” way of doing things will be provided. The driver exercise is targeted at non-PNP legacy hardware that has to do extra work to get a working instance of a device object pointer necessary for using the sysfs infrastructure.