Date: Sun, 11 Feb 2007 11:10:57 -0600 (CST) From: Stephen Montgomery-Smith <stephen@math.missouri.edu> To: Daniel Eischen <deischen@freebsd.org> Cc: "Eugene M. Kim" <freebsd.org@ab.ote.we.lv>, hackers@freebsd.org Subject: Re: sin()/cos()/tan() for kernel code? '_ 'a Message-ID: <20070211110815.O62469@math.missouri.edu> In-Reply-To: <Pine.GSO.4.64.0702110941580.19880@sea.ntplx.net> References: <45CED641.7020608@ab.ote.we.lv> <Pine.GSO.4.64.0702110941580.19880@sea.ntplx.net>
next in thread | previous in thread | raw e-mail | index | archive | help
On Sun, 11 Feb 2007, Daniel Eischen wrote: > On Sun, 11 Feb 2007, Eugene M. Kim 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? > > Can't you do this in userland? Teach moused? Since you will only need sin and cos evaluated to the nearest degree, if that, I suggest a simple look up table. There is also something called the CORDIC method, I think, but I suspect that the look up table will be so much easier to program, and negligable extra space overhead. Stephen
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20070211110815.O62469>