I started to write linux driver and i am confident on it now, but my interest now is to write lower-level driver (platform driver) for spi or USB or i2c controller. Is there any i can start writing to practice platform driver on linux PC. Can some suggest how to start writing platform driver on linux.
Thank you
A good way is to look at the existing drivers, look at the list of open bugs and start to fix them. That will give you a good introduction to the kernel, you will learn to work as part of a huge, distributed team (will look good on your CV) and you will help to make the world better, one line of code at a time.
The next step is then to find some unknown, unsupported hardware and write a driver for it. The start here is to copy an existing driver or extend it (depending on how "different" the hardware is).