using "bare" bsp option

Joel Sherrill joel.sherrill at
Wed Aug 9 20:41:06 UTC 2000

Ahmet Akkas wrote:
> Hi everybody,
> Before I ask my question, I want to tell you what I had right now.
> I built the RTEMS using Lucent's tools (compiler, assmbler, etc.) for
> a Lucent's 16000 DSP processor. Right now I have not created any bsp
> for it but I used bare bsp option to build the RTEMS's kernel.
> My question is the following: Is bare bsp option sufficent to able to
> compile a simple application and put it into the Lucent's simulator?

No.  The bare bsp has no io facilities, linker script, etc.  Look
in a recent snapshot at i960sim, sim68000, or h8sim for very simple 
BSPs.  i960sim and h8sim use "magic" devices inside the simulator to
get console IO.
> I should point out two things at this level. First, I realized that
> the shared library (under the ../c/src/lib/libbsp/shared )is not compiled
> and added to the built RTEMS library. As you know this library has
> initialization and console routines. I am planning to compile the files
> in this directory and add them into built RTEMS libraries.

libbsp/shared is POTENTIALLY shared files.  They are picked up via
VPATH in the BSPs that use them.  You choose whether or not to use
them on a per BSP basis.  Look at one of the 68k BSPs
and what how it uses VPATH to get some things from .,
and libbsp/shared. :)

> Second, right now I am not sure how to handle crt0.o file. In the RTEMS
> documentation, it is said that startsim.o will be used instaed of crt0.o.

crt0.o is only really responsible for a handful of things:
  + zeroing uninitialized memory
  + setting up a stack
  + calling boot_card.  Using arguments (0,0,&environ)
    seems to work best overall.
  + (optional) copying initialized data from a ROM location
    so you can rerun.

Again one of the simulators above is a good example.

> There is aslo crti.o file.

I think this is an artifact of the way gcc does some things on
some targets.  If you are going to do C++, then you will have
to make the magic for global constructors happen with your
toolset -- but first, survive a context switch. :)
> Please let me know your suggestions. I really appreciate it.

Sounds like you are making progress.  Has the C4x port in
the recent snapshots had any hints for another DSP port?

I would expect that by now you have a pile of comments for the
porting guide also. :)

> Thanks,
> Ahmet Akkas

Joel Sherrill, Ph.D.             Director of Research & Development
joel at                 On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
   Support Available             (256) 722-9985

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