From owner-freebsd-hackers@FreeBSD.ORG  Wed Sep 24 14:42:56 2003
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From: Vincent Jardin <vjardin@free.fr>
To: hackers@freebsd.org
Date: Wed, 24 Sep 2003 23:42:55 +0200
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Message-Id: <200309242342.55788.vjardin@free.fr>
Subject: BUS DMA sync
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Hi,

I try to understand the purpose of the PRE sync (BUS_DMASYNC_PREREAD, 
BUS_DMASYNC_PREWRITE).

I understand POST synchronization (BUS_DMASYNC_POSTREAD, 
BUS_DMASYNC_POSTWRITE)  when a device to memory or a memory to device 
transfert needs to be synchronized. However, what does a synchronization 
before a transfert mean ?

Regards,
  Vincent