linux-kernel - Re: [PATCH] pci: print out DMA mask info

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Date:	Fri, 10 Oct 2008 11:59:35 +0900
From:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To:	yinghai@...nel.org
Cc:	grundler@...isc-linux.org, jbarnes@...tuousgeek.org, mingo@...e.hu,
	tglx@...utronix.de, hpa@...or.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH] pci: print out DMA mask info

On Fri, 10 Oct 2008 11:40:51 +0900
FUJITA Tomonori <fujita.tomonori@....ntt.co.jp> wrote:

> On Thu, 09 Oct 2008 14:27:33 -0700
> Yinghai Lu <yinghai@...nel.org> wrote:
> 
> > Grant Grundler wrote:
> > > On Wed, Oct 08, 2008 at 04:02:23PM -0700, Yinghai Lu wrote:
> > >> so can find out what is DMA mask is used for pci devices in addition to
> > >> default setting.
> > > 
> > > I like the idea. I don't like the additional boot time output.
> > > 
> > > But I'm thinking this could be an option to lspci.
> > > lspci already knows about the /sys tree. Can PCI export the two masks
> > > (dma_mask and dma_consistent_mask) and something like "lspci -td"
> > > would dump those in a nice way?
> > > 
> > in boot log, it could link with driver, pci info...
> > > 
> > >> got:
> > >> aacraid 0000:86:00.0: using 32bit DMA mask
> > >> aacraid 0000:86:00.0: using 32bit consistent DMA mask
> > >> aacraid 0000:86:00.0: using 64bit DMA mask
> > >> aacraid 0000:86:00.0: using 64bit consistent DMA mask
> > 
> > and aacraid do 32bit at first then 64bit...
> > 
> > so put that in boot message could be useful too.
> 
> IIRC, aacraid uses 32bit dma_mask at startup then it executes a
> special command to get dma information from the card, and sets proper
> dma_mask. So the above message is not wrong for aacraid, I think.

Oh, what you wanted to say is, "pci uses 32bit dma_mask and
dma_consistent_mask by default so aacraid doesn't need to set dma_mask
and dma_consistent_mask at startup", then it's true. You can remove
it. But it's just harmless unnecessary code.

But again, I don't think this is a good reason to print such dma
information for everyone at boot time.
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