Linux drivers development
From ArmadeusWiki
This page summarizes all you need to know before starting to develop Linux drivers for your Armadeus board
Contents
[hide]Recommended reading before starting
We advise you to read (not necessarly understand ;-) ):
- Linux Device Drivers (3rd edition) book: http://lwn.net/Kernel/LDD3/
Adding your own drivers
Our custom drivers build is integrated to the Linux build system (kbuild). You can select, in the linux "menuconfig / xconfig" tool, which Armadeus drivers you want to add on your target.
$ make linux-menuconfig
Device Drivers --->
Armadeus specific drivers --->
Here is the way to add custom drivers:
- change current dir to your armadeus view
- in target/linux/modules/, add a directory for your driver (ex toto/)
- put reference to this directory in the target/linux/modules/Makefile and target/linux/modules/Kconfig files
- in toto/ put your driver source code and create 2 files, Kconfig and Makefile. (Use target/linux/modules/gpio/Makefile & Kconfig as examples.)
To compile all the custom modules, either launch:
$ make -C target/linux/modules/
or
$ make linux
Only make linux will install the modules in the target rootfs image
i.MX register access from driver
To access i.MX registers from your driver, please use the readw/readl/writew/writel helper functions. Take a look at at arch/arm/mach-mx2/apf27.c or arch/arm/mach-imx/apf9328.c to have examples.
Debug
- Activate debug messages (from pr_debug() function) on console:
# echo 8 > /proc/sys/kernel/printk
