hi i am working my way through "essential linux device drivers" it has an example of a driver for an led attached to the parallel port in the init function, a call to parport_register_driver is made, but it's not well explained whats going on here this function takes a pointer to a struct parport_driver with socalled attach and detach functions the attach function simply calls parport_register_device with a pointer to yet another function called led_preempt the book says "when the kernel finds the led board during led attach, it registers the device by invoking parport_register_device()" how does the kernel know if the led board is connected? if it finds something is connected to the parport, how does it know its the led board, and not, say, a printer? when is led_detach called? and what about led_preempt? can someone shed some light on this? the code im talking about can be found here
http://elinuxdd.com/~elinuxdd/elinuxdd.docs/listings/listing05.6.html i would like to try this out but dont know how to build the hardware to do that is there a simpler way i can try this out without much electronics work involved? thanks martin
