Now that I have access to the serial console on Samsung e60 reader let’s build a new linux kernel for it.
The e60 reader has an ARM processor, to compile the kernel we need a cross compilation toolchain.
The first option is to use the one Samsung released with the other sources. It must work, however I don’t really like the idea to run binaries from unknown sources.
The second option is to build our own toolchain, we often have to do that for systems that requires patches on the compiler.
Here, Samsung’s binutils look like they were taken between 2.17 and 2.18 release (they are named 2.17.50 but are still slightly different from this snapshot) but they don’t seam to embed homemade patches. As for ggc I didn’t take time to check.
I choose to use the emdebian cross-development toolchain lenny version. (As the article in the french open silicium magazine #1 about FriendlyARM proposes to do).
Installing the cross-development toolchain on debian
First the archive keys:
sudo apt-get install emdebian-archive-keyring
Then we add a
/etc/apt/sources.list.d/emdebian.list file with the following content:
deb http://ftp.uk.debian.org/emdebian/toolchains lenny main
deb-src http://ftp.uk.debian.org/emdebian/toolchains lenny main
The we update the package list to install the needed packages:
sudo apt-get update
sudo apt-get install libc6-armel-cross libc6-dev-armel-cross libstdc++6-armel-cross binutils-arm-linux-gnueabi gcc-4.3-arm-linux-gnueabi g++-4.3-arm-linux-gnueabi
That’s it ! We have now our cross-compilation toolchain installed from packages, so easy to update or remove.
The kernel sources
Samsung released it’s modified 220.127.116.11 version. By cloning the kernel 2.6.29.y git branch, I could quickly see that their changes applied well to the 18.104.22.168 version (the last in the branch).
In order to better sort the changes michel.s had splat them into several patches
(patchs on e60-open project). After a few trials I build a
series file allowing to apply those patches with
quilt or better to import them to a git branch with
git quiltimport. The order I choose allows to drop easily some patches (the last ones).
One particular point on those patches is that some include binary files:
fs/rfs/*.o a proprietary journaling layer over FAT. If you want my point ov vue, we don’t need that. After all we have free journaling file systems available and linux is able to mount something else than FAT over USB…
drivers/usb/gadget/file_storage.o also the corresponding
.c file was removed, the BSD/GPL license from the original code allows a binary distribution (however I didn’t check if Alan Stern’s name appears in the doc) but I’d have liked that Samsung give that source code.
Before compiling the kernel, we need the
mkimage utility from U-Boot. Here, Let’s build the U-Boot released by Samsung, and let’s just copy the
tools/mkimage to a location in our PATH (that’s the only install method I could find).
cp tools/mkimage ~/bin/
For the config, one of the patches includes a
.config. That file is a copy of
config_rfs so even without the previous patch, we can get Samsung’s config.
Finally we can compile!
make CROSS_COMPILE=arm-linux-gnueabi- CFLAGS="-march=armv4t -mtune=cortex-a8" CXXFLAGS="-march=armv4t -mtune=cortex-a8" ARCH=arm uImage
We can then load our kernel by following The kernel testing howto from e60-open project. To load the kernel we will need the following command:
sudo dnw arch/arm/boot/uImage
That’it, and it works ! Well almost, the kernel cannot find his modules. This will not be a big deal for the ones included in the sources (but the subject of a next post) but the
lib/modules/dhd.ko modules are not included in the sources while reporting a GPL license to the kernel.
Missing source code
The Samsung Open Source Release Center website has a contact form, but it does not seam to work (I even booted my netbook on windows to try with IE8 without success). After browsing the french e60 forum I found their email address and mailed them, no answer so far (not even automatic). Let’s wait …
We can compile a kernel for the e60 reader without using the cross tools from Samsung.
There still some work to load modules as the one on the reader are copiled for 22.214.171.124 and our kernel does not want to load them. (I’ve already done a few tests but that will be a next posts’ topic.)
But without the missing sources it will be hard for us to best use our e60 reader.
Update: I got an answer from Samsung, they updated the released archive. I still have to look at it.