Permalink
Switch branches/tags
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
86 lines (73 sloc) 4.5 KB
Embedded Linux Kernel Internal Package
--------------------------------------
+ bbb directory contains the following sub-directories:
- Kernel
|- patches - Contains the patches to be applied to the kernel & the configuration file.
Note: These patches are for the kernel version 3.12.9.
- Apps - Applications to be used for testing the driver
- Driver - Driver source codes used in the workshop
These code templates are used in the Linux Kernel Internals workshop conducted
at SysPlay eLearning Academy for You. For details on the various workshops,
check out at https://sysplay.in/index.php?pagefile=weekend_workshops, or
contact us at <workshop@sysplay.in>
For the slide sets from the workshop, visit:
https://sysplay.in/index.php?pagefile=elki_workshop_slides
Pre-requisites
--------------
+ Linux PC or VM on Windows
+ Minicom or Gtk term installed with baud rate of 115200, 8 data bits, No parity, 1 Stop bit.
+ Tftp sever on Host.
+ Beaglebone Black
+ Source code downloaded from sysplay ftp server.
+ Toolchain can be downloaded from http://releases.linaro.org/14.04/components/toolchain/binaries/gcc-linaro-arm-linux-gnueabihf-4.8-2014.04_linux.tar.bz2
Building the Kernel
------------------
+ Below are the steps for the same:
- Download the kernel source code from below link:
ftp://ftp.kernel.org/pub/linux/kernel/v3.x/linux-3.12.19.tar.bz2
- untar it with 'tar -jxvf linux-3.12.19.tar.bz2'.
- Copy the patches folder in kernel source code directory as per below command:
> cp -r patches <kernel_dir>/patches.
- Apply the patches to the kernel. Execute the following command in kernel source directory:
> quilt push -a
- Configure the kernel with below steps:
+ Copy the patches/beaglebone as .config in kernel top level directory.
+ make ARCH=arm menuconfig
- Compile the kernel with make ARCH=arm CROSS_COMPILE=<toolchain-prefix> zImage
- This will give you the zImage at linux-3.12.9/arch/arm/boot/
- Transfer this is to the board and reboot to boot with new kernel image.
Building the driver as a part of Kernel
---------------------------------------
+ In linux, drivers can be compiled in two ways - either as part of the kernel or as modules so that they
can be plugged dynamically into the kernel. Here, we will build the driver as the part of the kernel, so
that it is loaded during boot up. All the relevant code can be found at Templates/Kernel/.
+ Here, we will add a small driver to the kernel. Below are the steps:
- Copy the file char_driver.c to linux-3.2.19/drivers/char/.
- Edit the Kconfig file in drivers/char/ and add the following:
config MY_DRIVER
tristate "My Driver"
help
Adding this small driver to the kernel
- This will show up as My Driver in menuconfig which you can either build as part of kernel, or as a
module.
- Edit the makefile to add the following entry:
obj-$(CONFIG_MY_DRIVER) += char_driver.o
This will boil down to either obj-y, obj-m or obj-n, depending on the option selected in menuconfig.
- In char_driver.c, put some message in init_char() function and that message will be displayed during
kernel booting.
- Once, the modifications are done, configure the kernel with make ARCH=arm menuconfig. Under the device
drivers-> Character devices, there will be a option MY_DRIV0ER, just select it. Exit & save the config.
- This will add the CONFIG_MY_DRIVER=y in the .config file which will be used in Makefile. The Kconfig &
Makefile have been kept in the Templates/Kernel/ folder for your reference.
- Now, compile the kernel with make ARCH=arm CROSS_COMPILE=<toolchain-prefix>- zImage
- Boot the board with above Image and you should see the message which you added in init_char.
+ To test the driver, there is one application by name file_ops in Templates/Sourches/Apps/ directory. Compile
the application and run it on the board. You will see, it gives the ascii code for the last character of the string written.
Compiling the Driver Code
-------------------------
+ Now, intention is to build the kernel module using the kernel source code. Below are the steps:
+ cd Templates/Sources/Driver/
+ Open the Makefile & update the 'KERNEL_SOURCE' variable with the path of kernel directory.
+ Update the 'CROSS_COMPILE' with your toolchain prefix say 'arm-linux-'.
+ Execute 'make' and this should generate the .ko file. Transfer this to the board using tftp or scp.
+ Once transferred, insert the module with 'insmod <module_name.ko>'.