Date: Fri, 09 Apr 2010 17:41:37 +0300 From: Andriy Gapon <avg@freebsd.org> To: Scott Long <scottl@samsco.org> Cc: arch@freebsd.org, Rick Macklem <rmacklem@uoguelph.ca> Subject: Re: (in)appropriate uses for MAXBSIZE Message-ID: <4BBF3CA1.1040001@freebsd.org> In-Reply-To: <682A6F1E-31E3-4920-A66E-452221866945@samsco.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> <682A6F1E-31E3-4920-A66E-452221866945@samsco.org>
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on 09/04/2010 17:35 Scott Long said the following: > On Apr 9, 2010, at 8:29 AM, Andriy Gapon wrote: > >> on 09/04/2010 16:52 Scott Long said the following: >>> 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. >> 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. I actually meant not what drivers advertise but what they use in busdma. Or are those directly related? -- Andriy Gapon
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