[PATCH v2] cmd: pxe: add support for FDT overlays

[Tom Rini]

On Tue, Jan 05, 2021 at 09:14:24AM +0100, Neil Armstrong wrote:
> On 04/01/2021 17:21, Jernej Škrabec wrote:
> > Dne ponedeljek, 04. januar 2021 ob 15:41:17 CET je Tom Rini napisal(a):
> >> On Mon, Jan 04, 2021 at 03:33:43PM +0100, Neil Armstrong wrote:
> >>> This adds support for specifying FDT overlays in an extlinux/pxelinux
> >>> configuration file.
> >>>
> >>> Without this, there is no simple way to apply overlays when the kernel
> >>> and fdt is loaded by the pxe command.
> >>>
> >>> This change adds the 'fdtoverlays' keyword for a label, supporting
> >>> multiple
> >>> overlay files to be applied on top of the fdt specified in the 'fdt' or
> >>> 'devicetree' keyword.
> >>>
> >>> Example:
> >>>   label linux
> >>>   
> >>>     kernel /Image
> >>>     devicetree /soc-board.dtb
> > 
> > This should be "fdt /soc-board.dtb",
> 
> 
> Indeed, thx
> 
> > 
> >>>     fdtoverlays /soc-board-function.dtbo
> >>>     append console=ttyS0,115200 root=/dev/mmcblk0p2 rootwait
> >>>
> >>> This code makes usage of a new variable called fdtoverlay_addr_r used to
> >>> load the overlay files without overwritting anything important.
> >>>
> >>> Cc: Tom Rini <trini at konsulko.com>
> >>> Cc: Andre Heider <a.heider at gmail.com>
> >>> Cc: Jernej Škrabec <jernej.skrabec at siol.net>
> >>> Cc: Jonas Karlman <jonas at kwiboo.se>
> >>> Signed-off-by: Neil Armstrong <narmstrong at baylibre.com>
> > 
> > Tested-by: Jernej Skrabec <jernej.skrabec at siol.net>
> > 
> > With above fix:
> > Reviewed-by: Jernej Skrabec <jernej.skrabec at siol.net>
> > 
> >>> ---
> >>> Hi Tom,
> >>>
> >>> This is repost of my last year's attempt.
> >>> It fills a hole to allow loading FDT overlays using PXE/Extlinux without
> >>> using FIT.
> >>>
> >>> V2 adds documentation.
> >>
> >> Thanks for following up.  I assume this follows what the spec says for
> >> this file?
> > 
> > Which specs? Official extlinux configuration specs [1] don't say anything about 
> > device tree files, so anything related to that is an extension (I hope I found 
> > correct specs). I think this one is extremely useful, users can easily specify 
> > which overlay file(s) they want to be applied in a text file.
> 
> Indeed, it follows the spec by not breaking it and simply extends the already
> u-boot specific pxe format.

I could have sworn that the spec on freedesktop.org had been extended
for overlays, but I don't see it now.  Thanks!

-- 
Tom
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