[U-Boot-Users] dynamic setting of CONFIG_SYS_CLK_FREQ

Wolfgang Denk wd at denx.de
Mon Apr 26 15:03:23 CEST 2004

In message <408CF369.9050907 at intracom.gr> you wrote:
> >Well, but how do you present it to the user? Will "printenv" show all
> >variables mixed? So how does the user know which get saved and  which
> >not?  How  do  you  merge  both  with  the standard CLI and hush in a
> >consistent way? And allthis without  (significantly)  increasing  the
> >memory footprint _and_ keeping the code readable?
> >
> >
> Well, will the user care?

I hope you are joking here. Of course he will.

> Why should he know that the version or the clock variable is real?

He  must  know  which  variables  are  available  when  reading   the
environment  under Linux. He must know which variables can be changed
(with the changes showing some effect). Etc. etc.

> If he tries to change a read only variable it should be denied.

Per definitionem there should be no variables in the environment that
cannot be changed. Period.

I know that there is the big exception of "ver" (I had a weak  moment
when  I  alloed  for  that),  and there are the smaller exceptions of
serial# end ethaddr which are settable  only  once  (usually  by  the
vendor), but this is at least configurable.

> Since the variables are present at RAM but not in persistent storage
> the size of the environment is the same. As for the code footprint
> this is debatable. If someone needs this "feature" he can enable
> it explicitly. If not enabled everything should work as it were.

I think the concept of environment variables as we  have  so  far  is
conceptually  pretty  clean.  What you suggest is different, and does
not fit. That does NOT mean that your idea is bad - not at  all.  BUt
such  "automatic"  variables must be kept separated from the environ-
ment. They shall not be  mixed  in  the  display  of  the  "printenv"
command, and not be settable by "setenv".

Please feel free to implement new "printvar" and "setvar" commands as
optional extension, but I really don't see that much benefit. Already
now it is pretty ifficult to find a variable definition  in  a  long,
multi-page "printenv" output.

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd at denx.de
You can observe a lot just by watchin'.                  - Yogi Berra

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