[RFC PATCH 02/28] cli: Add LIL shell

[Michael Nazzareno Trimarchi]

Hi

On Wed, Jul 7, 2021 at 4:48 PM Marek Behun <marek.behun at nic.cz> wrote:
>
> Dear Tom, Sean, Wolfgang and others,
>
> here are some of my opinions for this discussion
>
> - I agree with Wolfgang that there are far better options than
>   a Tcl-like shell, if we want to add another language
>
> - I also think that instead of adding another language, it is more
>   preferable to improve the existing one. Adding a new language will
>   cause more problems in the future:
>   - I think it can end up with OS distributions needing to write
>     boot scripts in both languages, because they can't be sure which
>     will be compiled into U-Boot
>   - we will certainly end up with more bugs
>   - userbase will fragment between the two languages
>
> - I think we can start improving the current U-Boot's shell in ways
>   that are incompatible with upstream Hush.
>
>   The idea back then, as I understand it, was to minimize man-hours
>   invested into the CLI code, and so an existing shell was incorporated
>   (with many #ifdef guards). But U-Boot has since evolved so much that
>   it is very probable it would be more economic to simply fork from
>   upsteam Hush, remove all the #ifdefs and start developing features we
>   want in U-Boot. Is upstream Hush even maintained properly?
>   What is the upstream repository? Is it
>   https://github.com/sheumann/hush?
>

I think that hush is the one that is now in the busybox. I could spent
ten minutes this morning and this is my short list:

- we have several define that allow it to enabled e/o disable a lot of features
- we are talking about 11K lines compared to 3K (including comment)
- we have 25-30 configuration option on hush on busybox
- in u-boot code some of the problem was solved some time ago
- as describe is 68Kb, I think this consider all the option enables
- the code is different from what we have and what is there

I don't know if options like ENABLE_HUSH_JOB and ENABLE_MMU can partially
solve some of the problems described in the thread

* Sean *: You have spent more on this, can you please complete it.

Out of that. Do we have some script shell unit test in uboot?

Michael

> - even if we decide to stay with upstream Hush and just upgrade
>   U-Boot's Hush to upstream (since it supports functions, arithmetic
>   with $((...)), command substitution with $(...), these are all nice
>   features), it is IMO still better than adding a new language
>
> - one of the points Sean mentioned with LIL is that when compiled, it's
>   size does not exceed the size of U-Boot's Hush.
>
>   If we were to add new features into U-Boot's Hush, the code size would
>   certainly increase.
>
>   I think we should implement these new features, and instead of adding
>   a new language, we should work on minimizing the code size /
>   resulting U-Boot image size. This is where U-Boot will gain most not
>   only with it's CLI, but also everywhere else. Regarding this,
>   - we already have LTO
>   - Simon worked on dtoc so that devicetrees can be compiled into C code
>   - we can start playing with compression
>     - either we can compress the whole image for machines with enough
>       RAM but small place for U-Boot (Nokia N900 for example has only
>       256 KiB space for U-Boot)
>     - or we can try to invent a way to decompress code when it is
>       needed, for machines with small RAM
>
> Marek



-- 
Michael Nazzareno Trimarchi
Co-Founder & Chief Executive Officer
M. +39 347 913 2170
michael at amarulasolutions.com
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