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From: Denis Vlasenko <vda@ilport.com.ua>
To: Carlos Munoz <carlos@kenati.com>
Subject: Re: How can I link the kernel with libgcc ?
Date: Fri, 10 Mar 2006 12:37:35 +0200
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Cc: Lee Revell <rlrevell@joe-job.com>, Valdis.Kletnieks@vt.edu,
       linux-kernel@vger.kernel.org,
       alsa-devel <alsa-devel@lists.sourceforge.net>
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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