ECE 373 Assignment #4
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 device 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 system log that says it was loaded (maybe dmesg?). 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 device file (not the sysfs file) it should be given the current blink
rate integer.
e) If a positive integer is written to the device file, the driver should use that value as the new blink
rate, just the same as in (c). Note, this is the /dev entry, not the sysfs file.
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.
So you run and you run...
Turn these materials in to Github Classroom, or dropbox, by Monday, 10-May-2021 at 11:00pm:
1. All the code you used (including makefiles and scripts)
