MultiCharDev

Example of creating a cluster of character devices driver in Linux. Tested on kernel 4.1.15

Usage:

1. first copy the files to your local machine by
   $> git clone https://github.com/georgewayne/MultiCharDev
2. compile with make. if all goes well, you'll have kernel module named multi.ko
   $> make
3. use below command to monitor the kernel massages
   $> tail -f /var/log/kern.log
4. install the compiled kernel module. if sucessful, you'll see your new devices /dev/mydevname?.
   $> sudo insmod multi.ko
5. run the test program
   $> sudo ./test
6. try all choices (open, read, write, close) and exit the test program
7. remove the kernel module
   $> sudo rmmod multi

A sample log from /var/log/kern.log is below:

Jan 24 22:41:46 raspberrypi kernel: [98038.140842] mydevname0 sucessfuly created
Jan 24 22:41:46 raspberrypi kernel: [98038.141076] mydevname1 sucessfuly created
Jan 24 22:41:46 raspberrypi kernel: [98038.141273] mydevname2 sucessfuly created
Jan 24 22:41:46 raspberrypi kernel: [98038.141287] all 3 devices sucessfuly created
Jan 24 22:42:08 raspberrypi kernel: [98059.808933] Driver: open() device /dev/mydevname0
Jan 24 22:42:19 raspberrypi kernel: [98071.319973] Driver: read() device /dev/mydevname0
Jan 24 22:42:25 raspberrypi kernel: [98077.147588] Driver: write() device /dev/mydevname0
Jan 24 22:42:47 raspberrypi kernel: [98099.074007] Driver: open() device /dev/mydevname1
Jan 24 22:42:50 raspberrypi kernel: [98102.136020] Driver: read() device /dev/mydevname1
Jan 24 22:42:51 raspberrypi kernel: [98103.491231] Driver: write() device /dev/mydevname1
Jan 24 22:43:18 raspberrypi kernel: [98130.193675] Driver: open() device /dev/mydevname2
Jan 24 22:43:21 raspberrypi kernel: [98132.636033] Driver: read() device /dev/mydevname2
Jan 24 22:43:21 raspberrypi kernel: [98133.130868] Driver: write() device /dev/mydevname2
Jan 24 22:43:49 raspberrypi kernel: [98161.323873] Driver: close() device /dev/mydevname0
Jan 24 22:44:21 raspberrypi kernel: [98193.476500] Driver: close() device /dev/mydevname1
Jan 24 22:44:31 raspberrypi kernel: [98202.692468] Driver: close() device /dev/mydevname2
Jan 24 22:44:48 raspberrypi kernel: [98219.888206] mydevname0 unregistered
Jan 24 22:44:48 raspberrypi kernel: [98219.888382] mydevname1 unregistered
Jan 24 22:44:48 raspberrypi kernel: [98219.888543] mydevname2 unregistered
Jan 24 22:44:48 raspberrypi kernel: [98219.888594] all 3 devices unregistered