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Determine SGEN max. transfer size

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From	Josef Moellers <josef.moellers@ts.fujitsu.com>
Newsgroups	comp.os.linux.development.apps
Subject	Determine SGEN max. transfer size
Date	Thu, 19 Apr 2012 09:34:05 +0200
Organization	Fujitsu Technology Solutions
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Hi,

I'm currently writing some test programs for hard disk drives and I'm
sending commands using the SCSI GENERIC driver.

I'm a bit confused about the use of SG_GET_SG_TABLESIZE and the max.
possible transfer size.
I had been under the impression that the value returned through
ioctl(fd, SG_GET_SG_TABLESIZE, &someint)
multiplied with the system's page size would give me the absolute limit
of any size handled by the sgen layer, but when I removed the limit
(setting it to an arbitrary 1GB), the transfers just went fine ...

If, as I now assume, SG_GET_SG_TABLESIZE is only relevant if iovec_cnt
is non-0, how can I determine the maximum permissable transfer size?

Thanks,

Josef
-- 
These are my personal views and not those of Fujitsu Technology Solutions!
Josef Möllers (Pinguinpfleger bei FTS)
	If failure had no penalty success would not be a prize (T.  Pratchett)
Company Details: http://de.ts.fujitsu.com/imprint.html

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Determine SGEN max. transfer size Josef Moellers <josef.moellers@ts.fujitsu.com> - 2012-04-19 09:34 +0200

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