From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Mark Lobo <ntdeveloper2002@yahoo.com>
Cc: linux-scsi@vger.kernel.org
Subject: Re: kernel addresses
Date: 28 Oct 2002 23:26:14 +0000 [thread overview]
Message-ID: <1035847574.3550.109.camel@irongate.swansea.linux.org.uk> (raw)
In-Reply-To: <20021028230140.79410.qmail@web80305.mail.yahoo.com>
kmalloc memory comes out of the pool requested GFP_DMA selects the ISA
space, GFP_HIGH allows all 36bits (if I remember rightly). vmalloc comes
from the whole of memory space.
the highmem I/O stuff is a 2.4 patch some people use so that DMA aware
drivers that support the full 32bit DMA range can avoid bounce buffers.
This comes from a 2.4 transition thing. Older drivers assume memory they
access is always mapped (eg when doing PIO) so the scsi code makes sure
this is true. The bounce patch lets drivers that don't do PIO avoid
this.
2.5 does the job properly instead as part of the block rewrite
next parent reply other threads:[~2002-10-28 23:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20021028230140.79410.qmail@web80305.mail.yahoo.com>
2002-10-28 23:26 ` Alan Cox [this message]
2002-10-28 23:54 ` kernel addresses Mark Lobo
2002-10-29 0:22 ` Alan Cox
2002-10-29 0:36 ` Mark Lobo
2002-10-29 1:07 ` Alan Cox
[not found] <20021029010744.83318.qmail@web80301.mail.yahoo.com>
2002-10-29 9:46 ` Alan Cox
2002-10-28 21:22 Mark Lobo
2002-10-28 22:26 ` Alan Cox
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