Date: Sun, 11 Feb 2007 01:09:30 -0800 From: "Kip Macy" <kip.macy@gmail.com> To: "Eugene M. Kim" <freebsd.org@ab.ote.we.lv>, hackers@freebsd.org Subject: Re: sin()/cos()/tan() for kernel code? '_ 'a Message-ID: <b1fa29170702110109o2d1b165aj1896c0c2574950b8@mail.gmail.com> In-Reply-To: <45CED641.7020608@ab.ote.we.lv> References: <45CED641.7020608@ab.ote.we.lv>
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Trigonometry is seldom done with fixed point, which is the only way to
do it in the kernel (using the FPU is a no-no). I would write a perl
script to generate a lookup table for those functions - paste it into
a header and use that. HTH.
-Kip
On 2/11/07, Eugene M. Kim <freebsd.org@ab.ote.we.lv> wrote:
> Hello all,
>
> I am writing a mouse device driver for my Wacom tablet (Intuos 2 9x12).
> The tablet comes with a mouse and I managed to get valid coordinate data
> from the device. However, unlike usual mice, the coordinate system is
> tied not to the orientation of the mouse itself, but to the tablet,
> which acts much like a "mouse pad". So, for example, if I rotate the
> mouse 30 degrees to the left and move it left and right, the mouse
> cursor would move not horizontally, but to 2- or 8-o'clock.
>
> Fortunately the mouse also provides orientation data along with
> coordinate data, so the correct cursor movement could be calculated from
> it. The problem: The calculation needs trigonometry, but there seems to
> be no math library support in the kernel (I ran "grep -w cos" on the
> -CURRENT source tree, which turned nothing up).
>
> Does anyone have an idea on how to do this?
>
> Cheers,
> Eugene
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