On Tue, 6 Aug 2013 17:42:31 -0400 Tom Rini trini@ti.com wrote:
On Tue, Aug 06, 2013 at 11:22:22AM -0500, Dennis Gilmore wrote:
[snip]
The only way I could see having us write a file to disk with the environment working is if all boards implement standard variable to define the memory locations and that is compiled into the u-boot binary.
some variables that would need to be compiled in
fdt_addr fdt_addr_r
Why two?
from cmd_pxe.c /* * fdt usage is optional: * It handles the following scenarios. All scenarios are exclusive * * Scenario 1: If fdt_addr_r specified and "fdt" label is defined in * pxe file, retrieve fdt blob from server. Pass fdt_addr_r to bootm, * and adjust argc appropriately. * * Scenario 2: If there is an fdt_addr specified, pass it along to * bootm, and adjust argc appropriately. * * Scenario 3: fdt blob is not available. */
u-boot by default would load a dtb to fdt_addr but a user could at least in the pxe/extlinux case load their own dtb if the want/need to.
the only way a dtb would be optional is if fdtfile is not set
kernel_addr_r ramdisk_addr_r pxefile_addr_r scr_addr_r uenv_addr_r
this should allow for for people to use boot.scr uEnv.txt or pxe/extlinux
This is what I think we need to work towards. A board opting into this standard must set CONFIG_CMD_A/B/C (or maybe we add a CONFIG_SUPPORT_GENERIC_LINUX_DISTRO that does this in one of the fallback files, whatever) and provide the following variables PLUS a, and this needs some thinking I think, auto-boot tries to load said file from ... ?
We cannot provide a built-in environment that works for every distro and case, we want the distro to tell us things it knows, and we'll tell it what it can't easily know.
we absolutely can, I would like for u-boot to load a dtb before doing anything. u-boot should know what devices can be booted from and likely an order of preference. i.e. removable media through to fixed, and finally pxe.
i would like for u-boot to first try to load /boot/extlinux/extlinux.conf then /extlinux/extlinux.conf failing that try to load a /boot/uEnv.txt then /uEnv.txt and import that running with what is in it, then falling back to a /boot/boot.scr then /boot.scr then finally running dhcp, pxe get, and pxe boot.
its then up to the distro to provide one of the 3 configs to boot. or the system falls back to pxe and a network boot/install is done.
Dennis