Date: Sun, 30 May 1999 18:12:13 +0200 (MET DST) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: louie@TransSys.COM (Louis A. Mamakos) Subject: Re: PCI bus chanages from 2.2.x to 3.x/4.x and data corruption. Message-ID: <199905301612.SAA17097@labinfo.iet.unipi.it> In-Reply-To: <199905301719.NAA82586@whizzo.transsys.com> from "Louis A. Mamakos" at May 30, 99 01:18:48 pm
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> > > It may be a compiler optimisation. > > > > i think all memory-mapped registers should be declared "volatile" to > > avoid such things occur. I remember when i was looking at both the > > meteor and bt848 drivers, there was some confusion about it. > > Depending on when you looked, the stuff you excepted below probably > didn't exist. It's been more than a year now, I think, but I > introduced the macro and associated typedef when I changed the driver very likely. i have been using a home-grown bt848 driver (derived from some early version of the official one) for some time until the time i switched to 2.2.6. In any case: the use of "volatile" seems correct now so i wonder why/if the compiler "optimizes" out the sequence bt848->tdec = 0; bt848->tdec = something; or perhaps is the bt848 chip which requires some time to detect&react to the first write (and if i remember well, the data sheets are extremely confused on this register). cheers luigi -----------------------------------+------------------------------------- Luigi RIZZO, luigi@iet.unipi.it . Dip. di Ing. dell'Informazione http://www.iet.unipi.it/~luigi/ . Universita` di Pisa TEL/FAX: +39-050-568.533/522 . via Diotisalvi 2, 56126 PISA (Italy) http://www.iet.unipi.it/~luigi/ngc99/ ==== First International Workshop on Networked Group Communication ==== -----------------------------------+------------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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