[linux-dvb] Kernelspace floating pointer - was Re: Port of em28xx and xc3028 to new hybrid tuner framework.

Mauro Carvalho Chehab mchehab at infradead.org
Sat Sep 8 01:15:29 CEST 2007


Markus wrote:

> the em28xx uses the userland implementation since the current xceive
> reference drivers use floating point algorithms.

The usage of FP on DVB drivers is something that have been discussed for
quite a long time at the community. I've asked Linus about the
possibility of having a kernelspace driver using floating point. This
may eventually happen (and, in fact, it already happens on a few
drivers). There are, however, two points to consider:

a) care should be taken to preserve FP state by the driver, since kernel
won't do this by itself. This probably means that this may not be so
fast as userspace calculation (although I suspect that it will be faster
enough for the current needs);

b) FP is processor dependent. So, old 80386 processors without FP
instructions shouldn't work (IMO, this is not an issue ). Also, maybe we
may have some troubles on a few non-x86 architectures (ARM ?).

Cheers,
Mauro




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