On Monday 03 August 2015 23:42:20 Alexander Graf wrote:
On 31.07.15 09:52, Matwey V. Kornilov wrote:
31.07.2015 11:42, Matwey V. Kornilov пишет:
2. Add overlay support to U-Boot
I know 2A option. Merge DTB and DTOs in userspace using special script and then provide the result to u-boot for the next booting. This is what update-bootloader may do.
So SPI came in as an option here. What exactly would you envision the script that makes this easy to look like?
Imagine you have a SPI Flash controller on your SPI CS0 connection. Then you would need to also add the flash driver to your device tree. And because the flash chip is partitioned, you would also need to provide its partition table in the device tree.
This is just a single device tree overlay. And although it can be specified completely in the device tree, I would expect the partitioning be part of the kernel command line.
It gets incredibly complicated very quickly.
That said, I do agree that we could probably do a better job at this by giving users at least the chance to take 2 dtbs and have the boot loader merge them into one - so you have one for the board and one for "custom changes".
Thinking out loud here, there is another problem we have on U-Boot systems: You can only have a single kernel selected at any given time. There are 2 options out of that
1) Implement extboot support in our bootloader configuration tools 2) Use grub2 on top of u-boot
I'm in favor of option 2. And I haven't looked at it, but I wouldn't be surprised if you could convince grub2 to merge dtbs for you. If it does't we should probably extend it to be able to.
grub2 can only merge a commandline into the /chosen/ dtb node, thats it. I think with extboot support, you mean configuration via extlinux.conf, as outlined here: http://code.metager.de/source/xref/denx/u-boot/doc/README.distro I dont like the idea of chaining bootloaders ad infinitum. The vendor supplied bootloader (start.elf for RPi) is limited (no boot menu, no network boot ...), so it makes sense to put something on top, but thats it. Kind regards, Stefan -- Stefan Brüns / Bergstraße 21 / 52062 Aachen home: +49 241 53809034 mobile: +49 151 50412019 work: +49 2405 49936-424 -- To unsubscribe, e-mail: opensuse-arm+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse-arm+owner@opensuse.org