piCore for DUMMIES

[Yleisajattelija]

Those HAT-modules cannot handled with "Static device tree" -structure, and "Device tree overlay" -batch system is used for Rasberry.

U-boot supports DTO, but Linux not, so it's difficult to say how it works, but I can guess, that U-boot modifies Device tree file and transfers it as static structure to kernel:

(DTO is on 23 min. point of video)

https://www.youtube.com/watch?v=Nz6aBffv-Ek

[patrikg]

This thread was long time ago, with my first RaspberryPi working with uboot and nfs.
I was struggling with device tree. fdt.
https://forum.tinycorelinux.net/index.php/topic,21356.msg133578.html#msg133578

[Yleisajattelija]

This thread was long time ago, with my first RaspberryPi working with uboot and nfs.
I was struggling with device tree. fdt.
https://forum.tinycorelinux.net/index.php/topic,21356.msg133578.html#msg133578

I suppose, piCore is loaded by Rasberry image -loader:

https://www.raspberrypi.com/software/


Typically U-boot sets up memories and device drivers (fdt) and starts microprocessor multiprosessing before launching image from SD-card. Rasberry uses that "Device Tree Overlay" process, which probably modifies fdt dynamically for image. Rasberry OS uses same image loader than other distroes, and IF that mechanism works as it should be working, piCore should get updated fdt with fully functional python module to use for add-on boards.

But, there seems to be some problems with Rasberry 5, too:

https://www.tomshardware.com/best-picks/best-raspberry-pi-hats

[Yleisajattelija]

Rasberry is a product of "Rasberry Pi Foundation":

https://www.raspberrypi.org/about/

They seems to be nice people, and they want to support communal youth well-being.

So, I think they want to support other distroes possibility to use Rasberry Pi and I/O modules: Even if I/O module drivers for piCore are not working just now, it would be worth or try to buy some modules for Rasberry 3 B plus, I think.

[mocore]

Rasberry is a product of "Rasberry Pi Foundation":

https://www.raspberrypi.org/about/

what makes you think that ?

https://www.arm.com/partners/catalog/raspberry-pi

https://en.wikipedia.org/wiki/Raspberry_Pi_Holdings

Raspberry Pi Holdings plc is a British technology business focused on designing and manufacturing single-board computers (SBCs) and modules,

[Yleisajattelija]

Rasberry is a product of "Rasberry Pi Foundation":

https://www.raspberrypi.org/about/

what makes you think that ?

https://www.arm.com/partners/catalog/raspberry-pi

https://en.wikipedia.org/wiki/Raspberry_Pi_Holdings

Raspberry Pi Holdings plc is a British technology business focused on designing and manufacturing single-board computers (SBCs) and modules,

You might be right. Then I need alterantives, maybe Olimex?

[Yleisajattelija]

i will send "official" inquiry to Rasberry for supporting U-boot/barebox boot for tinycore.

Rasperry is technically healthy, and HAT-module system is what is needed. But I think bare HW and barebox boot is mandatory for lifetime tc support.

Of course few difficult security principles must first be handled somehow...

[patrikg]

It was not to difficult to compile uboot for raspberry pi.
And a was chainbooting uboot from the original boot rom.

What do you want to archive with uboot ??

I was using it because of lack of netbooting in the main boot rom.
Now a days Raspberry pi is supporting netbooting, with the newer ones.

I have seen that Home Assistant uses uboot for raspberry pi.
Don't know why ?

[Yleisajattelija]

It was not to difficult to compile uboot for raspberry pi.
And a was chainbooting uboot from the original boot rom.

What do you want to archive with uboot ??

I was using it because of lack of netbooting in the main boot rom.
Now a days Raspberry pi is supporting netbooting, with the newer ones.

I have seen that Home Assistant uses uboot for raspberry pi.
Don't know why ?
 

I think that just loading new image use current device drivers and memory setup. Loader (U-boot/barebox etc .) starts uP (= Arm on this case) on real time mode, sets up device drivers, sets up MMU and memories, switch to protected mode, load kernel on virtual memory space and (hopefully) jump to correct virtual memory address for kernel startup.

On PC systems, udev handles dynamic driver loading:

https://en.wikipedia.org/wiki/Udev

...so, mechanism to do so is already there. Embedded systems things are more difficult, and static device drivers are preferred on many cases.

Writing drivers is very difficult on add-on-HW, and because HW-cards with uP, memory and I/O is chaper than making new device depended software, TCP/IP and USB are nowadays used instead HW-bus. USB and TCP/IP drivers and memory allocation are already there, so it is how things are done.

Is it good or bad depends security issues....

[Yleisajattelija]

Rasberry answered, they won't release boot code (british are polite, so they didn't actually say so, but anyway...), but do support DTO-mechanism for other distroes.

I suppose linux kernel support DTO, but that's probably kernel option by parameters.

Does tc have DTO-support activated?

[Yleisajattelija]

Is there switch for DTO?

https://docs.kernel.org/devicetree/overlay-notes.html

Not easy for Olimex either:

https://forums.balena.io/t/how-to-load-device-tree-overlay-on-allwinner-board/366669

....but there is U-boot loading....

https://github.com/OLIMEX/OLINUXINO/blob/master/DOCUMENTS/OLIMAGE/Olimage-guide.pdf