Ticking away the moments...
Once the basics of a driver are in place, we can continue to add more features. This week, we'll add a bit of code that has the LED blinking on a timer. From HW 3, you should already have the LED control connected to the cdev callbacks, so most of the work is already done. Here, the aim is to have a driver that blinks the LED as long as some user process has the control file open.
Kicking around...
Here are your requirements:
a) When the driver loads, it creates the /dev/ece_led character device file (no mknod this time) and prints to the logfile that says it was loaded. It also checks for a module parameter blink_rate that gives a new default blinks-per-second rate, otherwise it has a default of 2.
b) When a user program opens the device file, LED0 starts to blink on a 50% duty cycle at the given rate per second. This blink should be controlled by a timer object.
c) If a new value is written to the module parameter by writing into the parameter entry in
/sys/module/<driver_name>/parameter/blink_rate, the blink rate will change.
d) If the user program reads the file it should be given the current blink rate integer.
e) If a positive integer is written to the file, the driver should use that value as the new blink rate, just the same as in (c).
f) If the data written is not a positive integer, the write callback should return the error EINVAL.
Also, make sure nothing bad happens if the program writes a 0.
