[SPAM] Xilinx Zynq-7000 : Help petalinux patch u-boot env vars

[RisingEdgeIndustries]

Thank you very much Xavier!  This reply was very helpful.  Yes, you are
correct regarding <configs/xilinx_zynq_virt_defconfig>.

What did you mean by the below statement?



*Or if you just want to change those variables you listed, you may
setCONFIG_IPADDR, CONFIG_SERVERIP, CONFIG_BAUDRATE, in the file you
said.But only those that include/env_default.h considers.*

Specifically, what did you mean by "only those that
include/env_default.h"?  Looking at env_default.h I don't see much.  Are
you saying if I add my own CONFIG_xxx environment vars they also have to be
in the env_default.h file?

I think patching a source file might be the easiest for me because I'm
booting a ramdisk image so I'm not storing any data outside of my image
binary so building these variables into the binary boot image seems ideal
for me.  Also, Xilinx provides a linux image build tool that builds linux
images for their parts and this tool allows you to script in software
patches to source files for u-boot and linux/kernel during the build
process.  This seems to fit into their expectations so I am trying to
figure out how to "patch" (modify) the u-boot source to have to include
some extra environment variables.

So (I think) what I really need to know is what the proper source file to
patch and add these environment variables to would be.  It's a little weird
because there are quite a few environment variables there already I don't
want to erase, I just want to append a couple new ones.

So if I add, for example, CONFIG_IPADDR to my
configs/xilinx_zynq_virt_defconfig is there anything else I would need to
check or do to ensure this flows through the build properly?

I also couldn't find the environment.rst in my docs - took a screenshot
below.  As an aside I'm using a Xilinx version of u-boot from the following
repo.

https://github.com/Xilinx/u-boot-xlnx


[image: image.png]

Thank you again so much for helping me!

Robbie Valentine
Electrical Engineer
RisingEdgeIndustries
(256) 244-4091


On Sat, Jun 11, 2022 at 12:35 PM Xavier Drudis Ferran <xdrudis at tinet.cat>
wrote:

> El Fri, Jun 10, 2022 at 11:32:59PM -0700, RisingEdgeIndustries deia:
> > Hello,
> >
> > I'm trying to update some of the u-boot environment variables when I
> build
> > my linux Image using petalinux for the zynq 7000 (zedboard).
> >
>
> Hello, not an expert, but I hope I can help and that people correct me i
> fI
> was to mislead you.
>
> > Looking at the configs folder I found the "xilinx_zynq_virt_defconfig".
> So
> > my first question is the following.  Does this file contain the
> environment
> > variables I see when I boot u-boot?  I want to add some environment
> > variables for u-boot.
> >
>
> No. You mean configs/xilinx_zynq_virt_defconfig, right ?
>
> This file is a summary of the .config file that the U-Boot project
> proposes to
> configure the build for the board.
>
> When you do
>
> make xilinx_zynq_virt_defconfig
>
> the file is copied to .config with the rest of options that are
> logical consequences of those in the file according to the rules in
> diverse Kconfig files. The make/autoconf/whatnot machinery gets them
> in .h files, link files... Makefiles recognize some, etc.
>
> So these are build time options. You can change them interactively
> (and break things) with
> make nconfig
> for example, and if you want to create a summary of .config like those
> in configs/ do
> make savedefconfig
> and you could cp the generated defconfig into configs with the proper
> name if that was needed.
>
> Environment variables are runtime options.
>
> > For example,
> > ipaddr = <my_ipaddr>
> > serverip = <tftp_server_ip>
> > etc....
> >
>
> Yes those look like environment variables, for runtime.
> Those can be embedded inside the U-Boot binary, and/or U-Boot
> can read them from different places. That's decided through
> build time options like those in configs/xilinx_zynq_virt_defconfig.
>
> You may want to read doc/usage/environment.rst
>
> > If this file is not the file one would modify could someone point me to
> the
> > correct place?
> >
>
> I'd say this is not the one or only one, but you might get away by
> adding some CONFIG_ENV_SOURCE_FILE=x here and then create a new file
> board/xilinx/zynq/x.env
>
> Or if you just want to change those variables you listed, you may set
> CONFIG_IPADDR, CONFIG_SERVERIP, CONFIG_BAUDRATE, in the file you said.
> But only those that include/env_default.h considers.
>
> > My ultimate goal is to use petalinux-devtool (which is yocto devtool -
> > https://docs.yoctoproject.org/ref-manual/devtool-reference.html) to
> update
> > u-boot so it contains my added environment variables.  This tool
> basically
> > downloads the xilinx u-boot repo and allows changes to be made via the
> > yocto devtool.  So that is a little background on why I'm trying to do
> this
> > modification this way.  The recommended approach from my silicon vendor
> > (Xilins) is to use this devtool to "patch" the u-boot source.
> >
>
> Maybe you want to patch include/env_default.h or (too complex?) build
> an external environment file to load at runtime (if you don't need
> trust verification) with mkenvimage -r ... and have it put in offset
> 0xE00000 in your boot media. But then you should add a copy somewhere
> (at 0?). Curious that your board has
> CONFIG_SYS_REDUNDAND_ENVIRONMENT=y but no CONFIG_ENV_OFFSET_REDUND.
>
>
> > So long story short, I have the source ready to be patched and built but
> I
> > don't know exactly what to patch (which source file) so when I boot into
> > u-boot I have the newly added environment variables loaded.
> >
>
> U-Boot is not Perl, but there's more than one way to do it...
>
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