Date: Thu, 4 Apr 2002 19:25:49 -0800 (PST) From: Matthew Jacob <mjacob@feral.com> To: "Justin T. Gibbs" <gibbs@scsiguy.com> Cc: Terry Lambert <tlambert2@mindspring.com>, Andrew Gallatin <gallatin@cs.duke.edu>, freebsd-current@freebsd.org Subject: Re: BUS_SPACE_MAXSIZE & isp driver. Message-ID: <Pine.BSF.4.21.0204041922470.78599-100000@beppo> In-Reply-To: <200204050321.g353Ku971739@aslan.scsiguy.com>
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On Thu, 4 Apr 2002, Justin T. Gibbs wrote: > >BUS_SPACE_MAXSIZE seems to be related to the 'largest xfer you will be allowed > >to do at one time'- which is wrong because MAXPHYS is larger. > > If you look at the x86 implementation, BUS_SPACE_MAXSIZE is only > used in the non-GNUC case and is not referenced (I don't think) > by any driver code. Even setting it to MAXPHYS is not truely > correct since at some point we will have to start supporting > transfer mappings that are larger than what can be mapped by > a single buffer. I never realized that there was such controversy > over this value... it was just put in so that I could have something > for the non-GNUC case. Yeah, but, uh, it'll blow up in one's face..... The question I have is what *should* we be using? Should BUS_SPACE_MAXSIZE be bumped up so that any dma allocation we attempt for a platform will fit within it? I mean, it's used in a lot of places, so clearly it must mean something, right? What are the semantics here? -matt To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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