Antwort: Re: regarding soft floating point support

deepa.vijayaraghavan at deepa.vijayaraghavan at
Tue Oct 5 10:06:41 CEST 2004

Hello Wolfgang,
     Thank you for the tip.. I had left missed the 'ifdef CONFIG_8xx' the 
last time. Now, the file libgcc_sf.a is not found. Only libm is found in 
the $TARGET_LIB. I think I need to make the RTAI build once again, with 
soft floating point?! I don't know how to do this. 
ppc_4xx is a fixed point processor and has no FPU. This is why I want to 
use soft floating point. 
Please tell me how I should proceed further.

Just took the ID from the README. Missed copying the rtai list. Sorry 
about that.

Thanks and Regards


deepa.vijayaraghavan at schrieb am Fri, 01 Oct 2004 13:25:17 
> Hello Mr.Grandegger,
>          I use IBM PPC 440 based ebony board with RTAI patched 
> linux-ppc-devel OS as target. I also have the ELDK installed in the 
> server. My application needs floating point to work. Could you please 
> me how to enable this? 
>         In the example fp_ppc_8xx, I changed the $TARGET_LIB in the 
> makefile, to $MY_PATH/eldk/ppc_4xx/usr/lib. But only the check 
> gets built. I know that I am missing something(may be many things:))..

There is also a "ifdef CONFIG_8xx" in the Makefile. Just comment
this line and the correspondig one with "endif".

>        If you could give me a rough picture of how soft floating point 
> works, and how to get this enabled for (I think I need to make a build 
> again?), it would be great!

You need to statically link against the libm (for functions like sin, cos,
etc.) the provided soft floating point library emulating the generic
floating point functions, which are executed by a FPU, if avaiable.

> I would like to take this opportunity to also thank you for all the help 

> you've provided through the RTAI mailing list already!

Thanks, you are welcome. But I  prefer that you ask your questions
on the RTAI mailing list as RTAI is a community project.


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