Date: Mon, 11 Feb 2002 13:13:21 -0800 From: Michael Smith <msmith@freebsd.org> To: j mckitrick <jcm@FreeBSD-uk.eu.org> Cc: freebsd-hackers@freebsd.org, freebsd-newbus@freebsd.org Subject: Re: Adding newbus abstraction to parallel port devices Message-ID: <200202112113.g1BLDL201611@mass.dis.org> In-Reply-To: Your message of "Mon, 11 Feb 2002 13:41:43 GMT." <20020211134143.A24762@dogma.freebsd-uk.eu.org>
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> last time I looked, the parallel port chipset driver (isa/ppc) uses > microsequences to handle the hardware control/data ports for the > parallel port. For anyone who is unfamiliar with these, they are macros > built from I/O port bitmasks to handle the necessary hardware > control to run the parallel port. > > The committer that wrote the parallel port driver said he used > microsequences because the driver was designed/implemented before > newbus. > > Since the purpose of the microsequences was (a) hardware abstraction and > (b) to increase speed, how could this be re-written to use newbus > instead without a performance loss? You wouldn't want to. I devised the microsequence mechanism (which Nicholas greatly expanded and actually implemented) to get around the problem whereby a peripheral driver knows what the hardware needs to do, but does not know how to make the hardware do it. This is orthogonal to newbus, which provides glue for building the device tree and the like. Regards, Mike -- To announce that there must be no criticism of the president or that we are to stand by the president right or wrong is not only unpatriotic and servile, but is morally treasonable to the American public. - Theodore Roosvelt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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