From mboxrd@z Thu Jan 1 00:00:00 1970 From: Grant Edwards Date: Mon, 11 Feb 2013 21:11:52 +0000 (UTC) Subject: [Buildroot] kernel drivers References: <1360613608.96975.YahooMailNeo@web164601.mail.gq1.yahoo.com> Message-ID: List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: buildroot@busybox.net On 2013-02-11, Zoran Djordjevic 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. http://lwn.net/Kernel/LDD3/ http://www.amazon.com/Linux-Device-Drivers-3rd-Edition/dp/0596005903 http://www.amazon.com/Linux-Kernel-Development-3rd-Edition/dp/0672329468 http://www.amazon.com/Writing-Linux-Device-Drivers-exercises/dp/1448672384 http://www.amazon.com/Essential-Device-Drivers-Sreekrishnan-Venkateswaran/dp/0132396556 http://www.linuxforu.com/tag/linux-device-drivers/ http://oldpapyrus.wordpress.com/2012/04/29/writing-linux-device-driver-tutorials/ -- Grant Edwards grant.b.edwards Yow! hubub, hubub, HUBUB, at hubub, hubub, hubub, HUBUB, gmail.com hubub, hubub, hubub.