[U-Boot] [PATCH 2/2] Enable PXE boot on meson-gxbb.

[Andreas Färber]

Am 18.04.2017 um 00:26 schrieb Vagrant Cascadian:
> DHCP the protocol is not at all u-boot specific, sure, but the boot
> method:
> 
> #define BOOTENV_DEV_DHCP(devtypeu, devtypel, instance) \
> 	"bootcmd_dhcp=" \
> 		BOOTENV_RUN_NET_USB_START \
> 		BOOTENV_RUN_NET_PCI_ENUM \
> 		"if dhcp ${scriptaddr} ${boot_script_dhcp}; then " \
> 			"source ${scriptaddr}; " \
> 		"fi;" \
> 		BOOTENV_EFI_RUN_DHCP \
> 		"\0"
> 
> I guess I was referring to "source ${scriptaddr}; " line, which is quite
> u-boot specific. I didn't realize that "DHCP" also had support for EFI
> loaded over the network.

DHCP just sets a filename that we can then load. What differs is where
it gets loaded and what gets done with it next.

> It seems unforunate that the EFI network boot is only a fallback to
> loading a boot script over the network, as boot scripts and EFI boot
> seem to me like two unrelated features.
> 
> When loading from MMC, I think the order goes something like EFI,
> extlinux, u-boot boot scripts.

Nope, boot.scr goes before EFI also in the MMC case. That way I can have
a boot.scr script on SD that applies overlays with fdt apply and then
calls bootefi manually. And if anything goes wrong with the overlay, a
simple exit from the GRUB prompt still boots me into a working system
via the default EFI boot.

Cheers,
Andreas

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