Re: How can I link the kernel with libgcc ?

[Carlos Munoz <carlos@kenati.com>]

Denis Vlasenko wrote:

> On Friday 10 March 2006 05:47, Carlos Munoz wrote:
>  
>
> > Lee Revell wrote:
> >
> >    
> >
> > > On Thu, 2006-03-09 at 19:25 -0800, Carlos Munoz wrote:
> > >
> > >
> > >      
> > >
> > > > I figured out how to get the driver to use floating point operations.
> > > > I included source code (from an open source math library) for the
> > > > log10 function in the driver. Then I added the following lines to the
> > > > file arch/sh/kernel/sh_ksyms.c: 
> > > >   
> > > >
> > > >        
> > > Where is the source code to your driver?
> > >
> > > Lee
> > >
> > >
> > >
> > >      
> > Hi Lee,
> >
> > Be warned. This driver is in the early stages of development. There is 
> > still a lot of work that needs to be done (interrupt, dma, etc, etc).
> >    
>
> What? You are using log10 only twice!
>
>        if (!(siu_obj_status & ST_OPEN)) {
> 		...
>                /* = log2(over) */
>                ydef[22] = (u_int32_t)(log10((double)(over & 0x0000003f)) /
>                                       log10(2));
> 		...
>        }
>        else {
> 		...
>                if (coef) {
>                        ydef[16] = 0x03045000 | (over << 26) | (tap - 4);
>                        ydef[17] = (tap * 2 + 1);
>                        /* = log2(over) */
>                        ydef[22] = (u_int32_t)
>                                (log10((double)(over & 0x0000003f)) / log10(2));
>                }
>
> Don't you think that log10((double)(over & 0x0000003f)) / log10(2)
> can have only 64 different values depending on the result of (over & 0x3f)?
>
> Obtain them from precomputed uint32_t log10table[64].
> --
> vda
>  
Hi Denis,

Yes, the driver code so far only uses log10 twice, but there will be 
more uses for it as I populate the rest of the tables. However, I think 
its use will be some what limited. I wasn't aware that the floating 
point registers are not saved. I'll investigate a way to create a table 
with pre-calculated log10 values.

Thanks,


Carlos
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/