From: Krzysztof Halasa <khc@pm.waw.pl>
To: James Bottomley <James.Bottomley@steeleye.com>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>,
SCSI Mailing List <linux-scsi@vger.kernel.org>
Subject: Re: Proposal for new generic device API: dma_get_required_mask()
Date: Sun, 20 Jun 2004 01:39:18 +0200 [thread overview]
Message-ID: <m34qp7glsp.fsf@defiant.pm.waw.pl> (raw)
In-Reply-To: <1087657251.2162.49.camel@mulgrave> (James Bottomley's message of "19 Jun 2004 10:00:50 -0500")
James Bottomley <James.Bottomley@steeleye.com> writes:
> Could you elaborate on this? In the current scheme the coherent mask is
> for descriptor allocation (i.e. dma_alloc_coherent()) and the dma_mask
> represents the bus physical addresses to which the device can DMA
> directly; there's not much more the DMA API really does, what do you
> think is missing?
The problem is that (depending on platform) the pci_map_* and dma_map_*
functions ignore both masks. An example of such platform is i386 :-)
It seems the masks are used on i386 for only one thing - consistent
dma mask is used for consistent allocations only, and normal dma mask
is not used at all.
The normal mask is used mainly on 64-bit platforms and the meaningful
values are 2^32-1 and 2^64-1. It's used by PCI-X device drivers to
enable DAC transfers. This is why it isn't used on 32-bit platforms.
--
Krzysztof Halasa, B*FH
next prev parent reply other threads:[~2004-06-20 2:01 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-06-17 14:08 Proposal for new generic device API: dma_get_required_mask() James Bottomley
2004-06-17 14:51 ` Meelis Roos
2004-06-17 15:28 ` Matthew Wilcox
2004-06-17 20:12 ` James Bottomley
2004-06-18 0:46 ` Krzysztof Halasa
2004-06-18 1:45 ` James Bottomley
2004-06-18 23:07 ` Krzysztof Halasa
2004-06-19 15:00 ` James Bottomley
2004-06-19 23:39 ` Krzysztof Halasa [this message]
2004-06-20 16:56 ` James Bottomley
2004-06-18 9:21 ` Russell King
2004-06-18 23:10 ` Krzysztof Halasa
2004-06-19 20:22 ` Russell King
2004-06-20 0:00 ` Krzysztof Halasa
2004-06-20 19:47 ` Russell King
2004-06-23 19:32 ` Krzysztof Halasa
2004-06-18 5:59 ` Jeremy Higdon
2004-06-18 14:19 ` James Bottomley
-- strict thread matches above, loose matches on Subject: below --
2004-06-17 14:52 Salyzyn, Mark
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