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Date: Fri, 09 Apr 2010 17:41:37 +0300
From: Andriy Gapon <avg@freebsd.org>
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To: Scott Long <scottl@samsco.org>
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Cc: arch@freebsd.org, Rick Macklem <rmacklem@uoguelph.ca>
Subject: Re: (in)appropriate uses for MAXBSIZE
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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