Hi, this has been discussed recently. For RTAI on MPC 8xx we provide the following example:
ftp://ftp.denx.de/pub/RTAI/contrib/fp_ppc_8xx.tar.bz2 It links statically with the libm and the soft-float library derived from libgcc. Hope it's useful. >-- Original Message -- >Subject: Doing floating point calculations in kernel space >From: Toni Van Remortel <t.vanremortel at ha.be> >Reply-To: t.vanremortel at ha.be >To: Linuxppc-Embedded <linuxppc-embedded at lists.linuxppc.org> >Date: Fri, 17 Oct 2003 09:15:39 +0200 > > > >Hi all, > >When I thought it was a /proc problem, it was a float problem. >The CPU (405GP) has no FPU, but I need to calculate sin and cos in a >kernel module. >Why? Well, we use a formula to draw figures (all deformed circles). >Those figures can be defined with only 6 parameters, which are passed >from the control-panel (in userspace) to the RTAI-powered kernel module. >That module calculates the X and Y positions, creates PWM signals from >it and outputs them to GPIO1 and 2. > >I don't see another approach to get this working, because the >control-panel isn't real time, while the kernel module is. So the module >needs to calculate the X and Y positions from the 6 parameters. > >To make it short: can I use floating points in kernel space? The info >I've found just tells me 'no', but I'm wondering if there are any >workarounds for this. >I did find some 'faster math functions' which don't require any sin or >cos anymore, but they do require floating points. > >A possible solution to me, is using 'unsinged long int' multiplied by >some factor of 10. > >Anybody a better solution? > >PS: might be a bit off topic here, sorry about that. >-- > Toni Van Remortel > Wetenschappelijk Medewerker - D-science lab > Real time Linux for embedded systems: http://linemb.d-sciencelab.com > Tel: +32 3 205 61 72 - Fax: +32 3 205 61 95 > E-mail: t.vanremortel at ha.be > > > Wolfgang ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
