[PATCH 11/11] bootm: Support string substitution in bootargs

[Wolfgang Denk]

Dear Simon,

In message <20201019135602.3943835-12-sjg at chromium.org> you wrote:
> In some cases it is necessary to pass parameters to Linux so that it will
> boot correctly. For example, the rootdev parameter is often used to
> specify the root device. However the root device may change depending on
> whence U-Boot loads the kernel. At present it is necessary to build up
> the command line by adding device strings to it one by one.
>
> It is often more convenient to provide a template for bootargs, with
> U-Boot doing the substitution from other environment variables.
>
> Add a way to substitute strings in the bootargs variable. This allows
> things like "rootdev=%U" to be used in bootargs, with the %U substitution
> providing the UUID of the root device.

Argh, no, please don't.

You add something unconditionally to common code which very few
people need.  U-Boot size is growing all the time because of such
... features.  This may be acceptable on the systems you have in
mind, but I consider this selfish.

Why do we have to add yet another non-standard way of substituting
variables in a string?  Can we not use alreay existing methonds
instead?

Why do you have to use "%U" in your template instead of for example
"${uuid}" ?



Best regards,

Wolfgang Denk

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