From: Roland Dreier <rdreier@cisco.com>
To: David Miller <davem@davemloft.net>
Cc: ralphc@pathscale.com, rolandd@cisco.com,
openib-general@openib.org, linux-kernel@vger.kernel.org
Subject: Re: Suggestions for how to remove bus_to_virt()
Date: Thu, 13 Jul 2006 09:02:47 -0700 [thread overview]
Message-ID: <adaodvttrvc.fsf@cisco.com> (raw)
In-Reply-To: 20060712.174013.95062313.davem@davemloft.net
> > A cleaner solution would be to make the dma_ API really use the device
> > it's passed anyway, and allow drivers to override the standard PCI
> > stuff nicely. But that would be major surgery, I guess.
> Clean but expensive, you should not force the rest of the kernel
> to eat the cost of something you want to do when it's totally
> unnecessary for most other users.
OK, fair enough.
> For example, x86 never needs to do anything other than a direct
> virt_to_phys translation to produce a DMA address, no matter what
> bus the device is on. It's a single simple integer adjustment
> that can be done inline in about 2 or 3 instructions at most.
<pedantic>Except x86 needs to handle systems with IOMMUs now...</pedantic>
> If you need device level DMA mapping semantics, create them for your
> device type. This is what USB does, btw.
Makes sense -- Ralph, I would suggest looking at USB as a model.
- R.
next prev parent reply other threads:[~2006-07-13 16:02 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-07-12 23:29 Suggestions for how to remove bus_to_virt() Ralph Campbell
2006-07-12 23:40 ` David Miller
2006-07-13 0:11 ` Roland Dreier
2006-07-13 0:40 ` David Miller
2006-07-13 5:46 ` [openib-general] " Muli Ben-Yehuda
2006-07-14 22:27 ` Ralph Campbell
2006-07-14 22:35 ` David Miller
2006-07-14 23:45 ` Ralph Campbell
2006-07-15 13:42 ` Stefan Richter
2006-07-13 7:45 ` Stefan Richter
2006-07-13 16:02 ` Roland Dreier [this message]
2006-07-13 16:37 ` Ralph Campbell
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