EBC Exercise 26 Device Drivers
Chapter 8 of the text  gives a nice example of a minimal device driver. The purpose of this lab is to implement that driver.
Minimal Device Driver Example
Follow the 5 steps given in section 8.1.4 on page 205. You can get a copy of Listing 8-1 here (ECE497_Listings_for_Embedded_Linux_Primer_Chapter_8). Once finished you will have a file called
.../drivers/char/examples and have the kernel configure file and Makefile updated for the new driver. See section 4.4 on page 89 for help with modifying the config files.
Note: There is a typo in Listing 8-2.
If you have created the crossCompileEnv.sh file and sourced it, all you have to do to make the modules is cd to the top of the kernel directory and then:
$ make modules
Mine took a while the first time as it compiles all the modules. The second it only took 31 seconds.
Moving to Beagle
On the beagle edit /lib/modules/2.6.32/modules.dep and add
Then copy the file
…/drivers/char/examples/hello1.ko on the host computer to
/lib/modules/2.6.32/kernel/drivers/char/examples/ on your Beagle. This can be done with a single command though you may have to mkdir the char/examples directory on the Beagle first.
$ cd …/drivers/char/examples $ rcp hello1.ko root@beagle:/lib/modules/2.6.32/kernel/drivers/char/examples
I suggest putting the rcp in a file since you may use it several times while developing your code.
Now, on the Beagle, modprobe the module and check the log file.
# /sbin/modprobe hello1 # dmesg | tail -4
You should see your Init message. And then...
# /sbin/modprobe -r hello1 # dmesg | tail -4
should show your Exit message.
Section 8.1.7 on page 211 of the text shows how to pass a parameter to a module. Modify your hello1.c to take a parameter as shown.
Try passing two parameters.
Play with the mod utilities listed in section 8.2 on page 212.
Section 8.3 on page 217 gives a longer example of how to use the file interface with modules. Implement the example. Be sure to fix the unsigned int format error.
- The major device number 234 is part of a range of unassigned numbers. What is the range?
- What's the new line added to
- What does
- How can your driver find what the minor device number is?