Re: [patch 2.6.26] /dev/hpet - fixes and cleanup

From: Clemens Ladisch
Date: Wed Jul 23 2008 - 03:44:52 EST

David Brownell wrote:
> * Tighten and correct the userspace interface code
> ...
> + only open comparators that have an interrupt, and can thus
> perform "real work"

This prevents userspace applications from doing mmap() on /dev/hpet
even if there is no interrupt.

This seems to be the only part of the userspace interface that is
used in practice. Because of the availability of POSIX timers, it might
make sense to deprecate the HPET ioctl interface.

> And re that kernel interface: IMO, worth having a relatively
> generic interface for hardware timers instead of inventing a new
> interface for each new bit of hardware.

AFAIK it was intended to be similar to the RTC callback interface, but
that was before the generic high-precision timer stuff was introduced.

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