[Q] Urukdroid 1.5: How do I build a custom kernel? ALT: What should be my rootdevice? - Gen8, Gen9, Gen10 Q&A, Help & Troubleshooting

I want to use a usb ethernet card (ASIX AX88xxx), so I need to build my own kernel. I also want sshd and root access, so I would like to use Urukdroid.
How do I do this? Alternatively: What could I use instead of Urukdroid?
I tried chulri's [HOWTO] Build custom kernel, libraries and applications on your own and it compiles fine. I also compiled it with builtin support for my USB ethernet card. (There are some warnings with both stock and my kernel config but chulri mentions in the thread that some of this is to be expected.)
I used the new zImage as the zImage for the UrukDroid 1.5 installer. It installs fine, but when it tries to boot Urukdroid, the Urukdroid bootimage shows but after "Switching to rootfs" the tablet restarts (stock Archos bootscreen shows) and boots the standard archos system. This happens with both the stock kernel config and my kernel config.
Is this my fault, because I have the wrong rootdevice in my kernel? (I installed it on internal storage, not on a sd card.) I'm a bit rusty when it comes to linux kernel builds. Where do I enter the rootdevice and which is the right rootdevice for Urukdroid on internal storage?
Then I tried chulri's build environment but replaced the linux kernel sources with the kernel soruce from Urukdroid 1.5. The result was the same: When Urukdroid switches the rootfs , the screen turns blank, the standard Archos boot image shows and the standard android system gets loaded.
I would be very grateful, if somebody could point me in the right direction. (I would be even more grateful for a zImage, but that is a bit much to ask and I rather would like to know my way around kernel builds...)
[EDIT] OK, the question about the root device is probably silly, since it has been AGES since this was compiled into the kernel. The Main Question still remains: How can I use my USB ethernet card?
Marcus

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Building a kernel with stock SDE + chulri works, but still no ethernet
Since I was unable to get a custom kernel for Urukdroid working, I reflashed the tablet with stock firmware and SDE.
I basically followed Chulri's Root easily your gen8 device
Then I built a custom kernel with compiled-in ethernet support and compiled-in usb device support for my ethernet card. Again just like Chulri says.
I used the resulting zImage together with chulri's initramfs.cpio.gz from the +rw kernel.
Thanks for the great HOWTOs, Chulri!
When I now boot the developer edition and connect to it via adb (How I miss urukdroid already ) this is the dmesg output for the usb ethernet card:
Code:
usb 2-1: new high speed USB device using musb_hdrc and address 2
usb 2-1: default language 0x0409
usb 2-1: New USB device found, idVendor=0b95, idProduct=1780
usb 2-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 2-1: Product: AX88178
usb 2-1: Manufacturer: ASIX Elec. Corp.
usb 2-1: SerialNumber: 000003
usb 2-1: uevent
usb 2-1: usb_probe_device
usb 2-1: configuration #1 chosen from 1 choice
usb 2-1: adding 2-1:1.0 (config #1, interface 0)
usb 2-1:1.0: uevent
asix 2-1:1.0: usb_probe_interface
asix 2-1:1.0: usb_probe_interface - got id
eth0 (asix): not using net_device_ops yet
eth0: register 'asix' at usb-musb_hdrc-1, ASIX AX88178 USB 2.0 Ethernet, 00:11:6b:73:75:ac
/root/archos/archos-gpl-gen8/linux/drivers/usb/core/inode.c: creating file '002'
hub 2-0:1.0: state 7 ports 1 chg 0000 evt 0002
hub 2-0:1.0: port 1, status 0100, change 0001, 12 Mb/s
usb 2-1: USB disconnect, address 2
usb 2-1: unregistering device
usb 2-1: usb_disable_device nuking all URBs
usb 2-1: unregistering interface 2-1:1.0
eth0: unregister 'asix' usb-musb_hdrc-1, ASIX AX88178 USB 2.0 Ethernet
usb 2-1:1.0: uevent
usb 2-1: uevent
So ethernet is still not working, but at least I got a lot further.
Does anybody have any ideas on how to go on from here?
Am I missing any userland components?
Any help would be greately appreciated.
I keep on trying to get it to work on my own and will post any progress.
Marcus

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Hi!
Same problems here form me with an FTDI chip.
The musb_hdrc thing is a bit tricky, here are some of my experiences.
You can alter the kernel config when building a custom kernel, but the msub_hdrc is built by default as a module, which is bundeled with the stock firmware, so if you for example want to change something this will mess up the whole stack.
The modules built are under lib/modules and i couldn't see them neither in rootfs nor in initramfs so they probably arrive on the device when you install the stock firmware (the step before you flash the custom initram and zImage in chulri's tutorial)
For example my problem is that I have an FTDI chip <-> CA-157 micro-A plug which is plugged in into a70IT's micro plug. But it only works if I plug the micro A without the attached FTDI chip and as a second step attach the FTDI chip
There is probably something connected to the state changes because first the musb needs to go to a_idle and the to a_host to pick the FTDI
This is the reasong why I started to investigate the state machine of musb but I faced a big problem, namely if I remove musb_hdrc.ko from lib/modules and compile my modified version in the kernel then nothing happens after host attached dmesg message. The funny thing is that the only modification is a verbose log level nothing serious. If the musb_hdrc.ko stays in lib/modules and I compile the kernel with my musb_hdrc for sure the module already loaded message comes up -> this is totally normal as we don't want to load it twice.
I think there are some let's call it archos specific things and not "dirty hacks" which prevents me to modifiy some drivers in the way I want it...
I tried to post some questions to the platform thread but I'm still too green for it
I gave an FTDI related thread where my problem is detailed...
It would be very useful for me if a senior could explain how the full custom firmware is built up. What stays from the stock part and what is overwritten, yes I know that th initramfs and zImage is overwritten but I'm interested could we for example build a full .aos like firmware file where the lib/modules and all othe content is defined by the platform developer...
I know the most of the post is off topic but I'm really interested to in customization of platform like this but still have to learn a lot...
br, sodjas

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THings that should be easy, never turn out to be easy on embedded devices.
Thanks for your insights on the topic, sodjas.
This nicely explains why I got stuck.
Somehow the things that should be easy, are never easy on embedded devices.
I will keep trying when I have some free time again....

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Hi,
inresting thread indeed...
Though i did not take a deeper look into the archos kernel structures, maybe the solution is much simpler... maybe it's more complex
When compiling a custom kernel/modules both must match in the end.
In other words all modules should be replaced with the ones of your new kernel.
Stock firmware uses squashfs so it's little tricky to remove or insert modules to the right place...
The best thing to start with custom kernel development would be Urukdroid which uses "real" rootfs on ext4. By using the SDCARD install method there's a comfortable way to modify the rootfs (replace modules etc.).
At least if you got a linux machine at hand.
Urukdroid uses links to point to the real modules here.
EDIT: Here are the Urukdroid 1.5.1 kernel sources
Not sure if there are kernel modules in initial ramdisk already... had to take a look.
Maybe you already knew this, maybe not... anyway could be helpful
Best regards,
scholbert

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True enough, the userland alone makes urukdroid a much better environment for experimentation...
But I only managed to compile a kernel according to chulri's HOWTO which works with the stock development environment.
I tried booting urukdroid with such a kernel but failed. The device did show the urukdroid boot screen and progress bar but then restarted and loaded the stock archos android environment.
Maybe I'm not doing my forum searches/gooogle searches right. I will try again. But how do I set up a cross compilation environment for urukdroid kernels?
Are the urukdroid developers using the build environment and kernel sources according to chulri and I just didn't chose the right mix of modules to compile?
I tried using chulri's build environment and replaced the linux kernel sources with the urukdroid kernel sources, but did not manage to compile a bootable kernel.
This doesn't get easier since archos modified the kernel sources and urukdroid probably has some special modifications, too.
There must be some information missing that I wasn't able to find yet. (Or maybe I am just stupid . Hey, I would welcome a nice insulting rant about now that tells me what a sucky noob I am and includes some nice links about how I can pull myself out of this swamp by my own bootstrings .)
EDIT: I just saw your edit, scholbert. Thanks for the helpful link. Could you help with setting up a cross compilation environment? Even just a few links and pointers would be welcome.
Are you saying that I should invest in an sdcard and manipulate the rootfs directly, instead of using the kernel update function of the tablet's developer boot menu? Or does the rootfs only help me including self compiled modules? Couldn't I just integrate the devices directly into the kernel, avoiding any rootfs manipulation?

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Hi,
yeah i think Urukdroid uses the same/similar environment.
In fact you'll have to, if you use propietary kernel modules from stock firmware (e.g. hdmi modules).
mmkhd said:
Could you help with setting up a cross compilation environment? Even just a few links and pointers would be welcome.
Click to expand...
Click to collapse
So you said you followed chulris way... you'll have to built a toolchain from the archos sources first.
How did you compile your kernel then?
Anyway here's another interesting post...
http://forum.xda-developers.com/showthread.php?t=978564&styleid=15
EDIT: The cross toolchain in fact is build from scratch using the buildroot system and the modified sources from archos.
Check this for more information about buildroot toolchain generation.
I wonder if someone already built a standalone cross toolchain ready to use on different linux systems. Might be a quite useful thing
mmkhd said:
Are you saying that I should invest in an sdcard and manipulate the rootfs directly, instead of using the kernel update function of the tablet's developer boot menu? Or does the rootfs only help me including self compiled modules?
Click to expand...
Click to collapse
You should always use the update function for kernel and initial ramdisk.
So using a sdcard system will just help you to modify the rootfs very easily (e.g. integrating the modules).
mmkhd said:
Couldn't I just integrate the devices directly into the kernel, avoiding any rootfs manipulation?
Click to expand...
Click to collapse
Honestly i'm not sure if this will work properly for any peripheral... AFAIK some drivers are required to be loaded as a module.
Anyway, i guess i will also do some kernel work the next months... if i find useful information i'll keep you informed
EDIT: Ah, i nearly forgotten... there are no modules in inital ramdisk.
Everything is located in /lib/modules (as sodjas already pointed out).
Cheers,
scholbert

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Hi mmkhd,
i don't know if you made some progress with this issue.
Anyway, i build an Archos specific standalone toolchain in the meantime.
Attached are the modules for Asix based USB2LAN adaptors.
Works very well with UrukDroid 1.5.1 on my A101.
Though you'll have to load the modules and setup the network manually at the moment.
At the shell:
su
insmod mii.ko
insmod usbnet.ko
insmod asix.ko
ifconfig eth0 xxx.xxx.xxx.xxx
You'll have to set the gateway and nameserver as well to use your browser.
I'm working on an automated solution...
Regards,
scholbert