Date: Fri, 9 Apr 2010 08:35:18 -0600 From: Scott Long <scottl@samsco.org> To: Andriy Gapon <avg@freebsd.org> Cc: arch@freebsd.org, Rick Macklem <rmacklem@uoguelph.ca> Subject: Re: (in)appropriate uses for MAXBSIZE Message-ID: <682A6F1E-31E3-4920-A66E-452221866945@samsco.org> In-Reply-To: <4BBF39C7.4050308@freebsd.org> References: <4BBEE2DD.3090409@freebsd.org> <Pine.GSO.4.63.1004090941200.14439@muncher.cs.uoguelph.ca> <07A7155D-0836-4D8C-BCF4-70FC16C77B69@samsco.org> <4BBF39C7.4050308@freebsd.org>
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On Apr 9, 2010, at 8:29 AM, Andriy Gapon wrote: > on 09/04/2010 16:52 Scott Long said the following: >>=20 >> Storage drivers are insulated from the details of MAXBSIZE by GEOM = honoring >> the driver's advertised max-i/o-size attribute. What I see when I = grep through the >> sources are mostly uses in busdma attributes, which themselves = probably came >> via cut-n-paste from prior drivers. I can't come up with any = explanation for that >> which makes good design sense, so I'll agree that storage drivers = shouldn't >> reference MAXBSIZE. >=20 > Should DFLTPHYS be used there? > Or is there a better DMA-specific constant? > Or, perhaps, each driver should just use its won private constant = based on its > hardware capabilities? Each driver should be advertising its own maxio attribute, with the = exception of CAM drivers. Advertising is optional in CAM, and is defaulted to = 64k. But yes, each driver should define and use its own constants here. Scott
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