u-boot purpose question

[RuralHunter]

Hi,

I got a Phicomm N1 TV Box, which is Amlogic S905D. I'm trying to build libreelec/coreelect for it. I saw there is a step in the build script to build and write the u-boot to the header of the output disk image.

I don't understand the purpose of this step. In my understanding, u-boot is already in the NAND of the box. What's the purpose to write it into the disk image? Is this step needed for my device? Currently I can see these u-boot env variables with my device:

start_autoscript=if usb start ; then run start_usb_autoscript; fi; if mmcinfo; then run start_mmc_autoscript; fi; run start_emmc_autoscript;
start_emmc_autoscript=if fatload mmc 1 1020000 emmc_autoscript; then autoscr 1020000; fi;
start_mmc_autoscript=if fatload mmc 0 1020000 s905_autoscript; then autoscr 1020000; fi;
start_usb_autoscript=if fatload usb 0 1020000 s905_autoscript; then autoscr 1020000; fi; if fatload usb 1 1020000 s905_autoscript; then autoscr 1020000; fi; if fatload usb 2 1020000 s905_autoscript; then autoscr 1020000; fi; if fatload usb 3 1020000 s905_autoscript; then autoscr 1020000; fi;

Is it OK if I skip the u-boot writing step and just put the s905_autoscript and other necessary files in the root of the disk image the burn to the sdcard? I just want it boot into the libreelec/coreelect on the sdcard.

[balbes150]

For LibreELEC, this is possible.

[RuralHunter]

1 hour ago, balbes150 said:

For LibreELEC, this is possible.

OK, I will try it. Btw, what's the purpose of the u-boot writing step for other than libreelec/coreelec?

[balbes150]

If u-boot is present, these images can be run on any hardware where it is missing or corrupted, or there is a desire of the user to use the new version of u-boot-2019.

[RuralHunter]

9 minutes ago, balbes150 said:

If u-boot is present, these images can be run on any hardware where it is missing or corrupted, or there is a desire of the user to use the new version of u-boot-2019.

Got it! Thanks!

[RuralHunter]

@balbes150

One more question, how does it work to use a new version of u-boot on the disk? Is there a step in the boot process of the u-boot in the NAND, to check and run another u-boot on the disk?

[balbes150]

3 hours ago, RuralHunter said:

One more question, how does it work to use a new version of u-boot on the disk? Is there a step in the boot process of the u-boot in the NAND, to check and run another u-boot on the disk?

Yes, see u-boot documentation.

[RuralHunter]

56 minutes ago, balbes150 said:

Yes, see u-boot documentation.

OK, thanks a lot!