Am 14.06.2018 um 13:04 schrieb Michael Mrozek EvilDragon@openpandora.org:
Am Donnerstag, den 14.06.2018, 12:55 +0200 schrieb H. Nikolaus Schaller:
Hi,
I also think we should put the Pyra-U-Boot sources to our gitlab so we can start adding Pyra-Specific stuff (bootlogo, mini charger, menu, etc.) to it.
Well, you can't add this to U-Boot. U-Boot can't drive a MIPI display (unless you back-port a lot of thing from kernel to u-boot).
Yes, and that's exactly what we did with the Pandora, for example. Initialize the display - otherwise, you can't show a boot menu where you can choose to boot from multiple sources.
You can, do that in the initrd/initramfs and can even write shell script code for that.
Much easier to maintain. And you can boot from SD, USB, Network, WLAN or whatever the kernel supports.
So it simply adds another stage of booting
BootROM -> MLO -> U-Boot -> Kernel from partitions U-Boot can search BootROM -> MLO -> U-Boot -> Kernel with initramfs -> final Kernel from whichever partition
So this should all go to the inird where you can load the panel driver kernel module.
That's too late for a boot menu, as then the kernel has already been loaded.
No. The kernel from initramfs can load another kernel through kexec.
Unless it's possible to choose a kernel and boot partition AFTER initrd.
Yes, that is basically the only reason why anyone needs an initramfs. Besides speed for headless embedded systems.
BR, Nikolaus