command line parameters

[Joel Sherrill]

nir levy wrote:
> Hi All,
>
> I am running RTEMS on QEMU emulator and i am using grub for booting ( 
> similar to most descriptions on the net for doing so).
> However, i could not find a way to send command line parameters for the 
> RTEMS applications i am running.
> I have tried to specified them in the GRUB configuration file ( after 
> the program name) but they don't seem to be pass to the application in 
> the Init procedure ( i have checked the c_rtems_main and the procedure 
> in the boot_card and they don't get there as well). I assume the problem 
> might be in the grub but if anyone ever succeed doing it and can help me 
> with that or advice on the issue it will be nice.
>   
There is no main() in an RTEMS application.  So the idea of
what to do with command line parameters is a bit vague.

Some boot loaders pass in a pointer to a data structure which
is used by the BSP.  U-Boot comes to mind in this case.

Right now, it is the responsibility of the BSP early start
code (usually named start.S) to invoke boot_card() with
argc, argv, and environ.  Right now, this information disappears
in boot_card() because there is no defined way to make it
available to the application.

I looked at this a while back and didn't have any real
example invoking environments to test with so left it
alone.  My thoughts were:

+ conditional compile argc, argv support in bootcard.c
    since it is unused baggage for most BSPs.  BSPs which
    want to and can support argc, argv can enable it.

+ Define a set of public variables which are the
   bsp or boot argc, argv, and environ values.

Getting the info from grub to pc386's start code
and to boot_card() makes it possible to address the
more general issue of what to do with them when they
are available.

I hope this has encouraged you to modify the BSP
to transfer the info from grub through start.S to
boot_card and help define the mechanism. :-D

FWIW another way I have seen is to prompt a user
for command line arguments.  Then convert that
string into argc/argv format to pass into a
main that was renamed to XXX_main().  This is a
relatively painless way to port UNIX main()'s to
RTEMS especially for testing purposes.  I am
thinking that since at least ttcp has code already
to do this and I have copied it at least once, that
is makes sense to generalize it and make it
part of libmisc.

--joel

> Thanks in advance.
>
> Best,
> Nir
>
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