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Re: [avr-libc-dev] RE: [bug #17216] change to the ../util/delay.h header

From: Joerg Wunsch
Subject: Re: [avr-libc-dev] RE: [bug #17216] change to the ../util/delay.h header for increased functionality
Date: Wed, 19 Aug 2009 06:14:40 +0200
User-agent: Mutt/1.5.11

As Weddington, Eric wrote:

> > But now that it works, can we update the <util/delay.h> to use it?
> Patches welcome.

The big thing I'm seeing with __delay_cycles is: How to *detect* it
from <util/delay.h>?

Either, the patch (and future public implementation) can "announce"
itself by the existence of a preprocessor macro, so applications could
e.g. write

#if defined(__HAVE_DELAY_CYCLES)
  __delay_loop_1(n / 3);

(this would IMHO be the best solution), or we have to rewrite
avr-libc's source code to derive the actual <util/delay.h> from a file
named delay.h.in, where the final file is generated at build time,
based on some autoconf probed compiler feature.  Obviously, this is
more effort to implement, and it will only work provided the compiler
avr-libc has been configured for is the same avr-libc is then going to
be used with.

cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)

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