[Buildroot] kernel drivers
grant.b.edwards at gmail.com
Mon Feb 11 21:11:52 UTC 2013
On 2013-02-11, Zoran Djordjevic <djdjdjole at yahoo.com> wrote:
> What I would like to know is how can I incorporate some new kernel
> driver (having it's source) into kernel build?
IMO, the easiest way to work on kernel stuff is to not use buildroot
to build the kernel. I do my kernel development outside of buildroot.
[There have probably been recent changes I don't know about that make
kernel development using buildroot easier, but it used to be a bit
awkward.] When you are finished testing your kernel changes, you can
do one of two things:
1) Combine your kernel with the root filesystem built by buildroot.
If you're using U-Boot, this is trivial: you can create a "multi"
uImage file (outfile.uImage) that contains the kernel image
(vmlinuz) and the root filesystem image (rootfs.cpio.gz):
mkimage -A arm -O Linux -T multi -C none -n "My kernel+rootfs image" -d zImage:rootfs.cpio.gz outfile.uImage
2) Zip up the modified kernel sources and configure buildroot to use them
to build your "production" kernel along with your rootfs.
> First, where should I put it in kernel source tree, then can I
> compile it independently, without rebuilding whole kernel (I imagine
> modules can do the job)?
You can either develop it as a module or as an in-kernel driver. In
either case, you don't have to rebuild the whole kernel when you make
changes to your driver.
If you develop it in-kernel when you modify your driver you _will_
have to recompile it and re-link the kernel (e.g. "make vmlinuz") and
then reboot to try out the new kernel.
If you develop it as a module, you can unload/reload the module to do
your testing. To save on resources, many embedded systems don't
support module loading/unloading (it's your memory, your choice).
> How can I compile it as a module or to be more precise, do I write
> driver in some special way to be a module?
Yes, drivers that are to be buildable as modules have to be written in
a special way. But, the extra code required to be module is simple
and it's not difficult to do.
Some of these references are getting a bit old, but still have a lot
of good info. Also don't foreget about /usr/src/linux/Documentation.
Grant Edwards grant.b.edwards Yow! hubub, hubub, HUBUB,
at hubub, hubub, hubub, HUBUB,
gmail.com hubub, hubub, hubub.
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