[U-Boot] [PATCH] pxe: implement fdtdir extlinux.conf tag

[Tom Rini]

On Thu, Jan 23, 2014 at 12:55:27PM -0700, Stephen Warren wrote:
> From: Stephen Warren <swarren at nvidia.com>
> 
> People who write (or scripts that auto-generate) extlinux.conf don't
> want to know about HW-specific information such as FDT filenames. Create
> a new extlinux.conf tag "fdtdir" that specifies only the directory where
> FDT files are located, and defer all knowledge of the filename to U-Boot.
> The algorithm implemented is:
> 
> ==========
> if $fdt_addr_r is set:
>   if "fdt" tag was specified in extlinux.conf:
>     load the FDT from the filename in the tag
>   else if "fdtdir" tag was specified in extlinux.conf:
>     if "fdtfile" is set in the environment:
>       load the FDT from filename in "$fdtfile"
>     else:
>       load the FDT from some automatically generated filename
> 
> if no FDT file was loaded, and $fdtaddr is set:
>   # This indicates an FDT packaged with firmware
>   use the FDT at $fdtaddr
> ==========
> 
> A small part of an example /boot/extlinux.conf might be:
> 
> ==========
> LABEL primary
>         LINUX zImage
>         FDTDIR ./
> 
> LABEL failsafe
>         LINUX bkp/zImage
>         FDTDIR bkp/
> ==========
> 
> ... with /boot/tegra20-seaboard.dtb or /boot/bkp/tegra20-seaboard.dtb
> being loaded by the sysboot/pxe code.
> 
> Signed-off-by: Stephen Warren <swarren at nvidia.com>

My only real concern is that
http://www.freedesktop.org/wiki/Specifications/BootLoaderSpec/ is as
best I can see the spec for extlinux.conf and it doesn't talk about this
tag.  So while it sounds like a good idea, if we implement it and it's
not documented outside of U-Boot, will anyone use it?

-- 
Tom
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