Has anyone tried doing a Yocto build for Kobo?

[OrangeWindies]

I'm wondering if anyone here has done any work on using Yocto to build a system image for a Kobo reader.

I'm kind of interested in having a clean and relatively modern base to develop on for the Clara HD, since I'm not interested in preserving the e-reader functionality.

NXP's Yocto BSP is based on Yocto 3.0 (Zeus) and Linux kernel 5.4, which is much more recent that the kernels shipped by Kobo. That BSP should contain all the necessary support for the i.MX6SLL processor in the Clara HD and readers with similar hardware.

It seems that someone has added device tree configuration for the Clara HD in mainstream Linux kernels (on the 5.7 branch) but mainstream kernels will be lacking support for NXP's special hardware. The particular problem there would be the EPDC e-ink controller.

I've got a fair amount of experience with Yocto but that's on our own hardware where we have all the schematics and data sheets. I fear it might be tricky to get all the relevant information to get the Clara HD's hardware working, unless it's sufficiently similar to the NXP evaluation kit design.

[NiLuJe]

I know of *one* eReader based on a semi-recent Yocto + NXP image: that's the reMarkable, and it runs on Linux 4.9 (which is what the official NXP+EPDC tree jumped to after the 4.1 used on Kobo).

That may be worth looking into, as the SDK is pretty much what Yocto's buildsystem outputs, IIRC (I'm, err, not necessarily a fan of Yocto, then again, not particularly familiar with it either, as I've never really had cause to use it ).

(Also, the rM's app also runs on Qt5 like Kobo's Nickel).

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TL;DR: Getting the userland up-to-date should be "trivial". The kernel, eeeh, might be trickier. Especially since Kobo themselves apparently barely touch it, AFAICT, that's left entirely at the mercy of NTX, their OEM.

[OrangeWindies]

Originally Posted by NiLuJe

I know of *one* eReader based on a semi-recent Yocto + NXP image: that's the reMarkable, and it runs on Linux 4.9 (which is what the official NXP+EPDC tree jumped to after the 4.1 used on Kobo).

Interesting...

Originally Posted by NiLuJe

(I'm, err, not necessarily a fan of Yocto, then again, not particularly familiar with it either, as I've never really had cause to use it ).

Yocto is a complicated beast, in my experience it either makes things very easy or very difficult. Pretty good for just getting kernels and normal software built and installed though.

[geek1011]

Originally Posted by OrangeWindies

Yocto is a complicated beast, in my experience it either makes things very easy or very difficult. Pretty good for just getting kernels and normal software built and installed though.

I personally prefer buildroot for most projects.

[NiLuJe]

Yup, my first instinct would be to turn to BR, too .

(FWIW, Amazon also ended up moving to a Yocto-ish setup (from a completely custom workflow, AFAICT) when they started tightening the screws on the Kindle ).

[andi45]

If you want more recent kernels for the Kobo Clara HD,

there is basically
https://github.com/akemnade/linux
branches kobo/merged-5.X
currently kobo/merged-5.8

The EPD works.
There is also the fork of xf86-video-fbdev which handles refreshes here:
https://github.com/akemnade/xf86-video-fbdev

[OrangeWindies]

Originally Posted by andi45

If you want more recent kernels for the Kobo Clara HD,

there is basically
https://github.com/akemnade/linux
branches kobo/merged-5.X
currently kobo/merged-5.8

The EPD works.
There is also the fork of xf86-video-fbdev which handles refreshes here:
https://github.com/akemnade/xf86-video-fbdev

Thanks for the info, I might give that a try when I get some time to work on this stuff again.

[OrangeWindies]

Originally Posted by andi45

If you want more recent kernels for the Kobo Clara HD,

there is basically
https://github.com/akemnade/linux
branches kobo/merged-5.X
currently kobo/merged-5.8

The EPD works.
There is also the fork of xf86-video-fbdev which handles refreshes here:
https://github.com/akemnade/xf86-video-fbdev

After spending a while looking getting the NXP kernel to work it seems like it will involve backporting quite a few drivers from 5.7 to 5.4. Not a lot of fun.

So maybe it would be better to go with the newer kernels that you suggested. What bootloader are you using? Is it the existing U-boot from the Kobo or are you building a newer u-boot-imx from NXP's sources?

[andi45]

Originally Posted by OrangeWindies

After spending a while looking getting the NXP kernel to work it seems like it will involve backporting quite a few drivers from 5.7 to 5.4. Not a lot of fun.

So maybe it would be better to go with the newer kernels that you suggested. What bootloader are you using? Is it the existing U-boot from the Kobo or are you building a newer u-boot-imx from NXP's sources?

I am using the plain kobo bootloader. It has some pitfalls, but you can work around them or patch them away. Basically, you have to call load_ntxkernel and then overwrite that using the standard load command.

There is also the branch e60k02 at git://git.goldelico.com/letux-uboot.git
which has some of the pitfalls removed. I need to check which configuration was used. I think it is mx6sll_ntx_lpddr2_512m_defconfig
My setup (including dualboot) is described at https://misc.andi.de1.cc/kobo

[andi45]

just one note:
there is a kobo_defconfig for these kernels which includes the necessary drivers

[OrangeWindies]

Months later, I finally got this finished.