linux-kernel - Re: [PATCH 0/3] Add API for weak DMA masks

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Date:	Thu, 1 May 2008 17:47:26 +0200
From:	Michael Buesch <mb@...sch.de>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Jesse Barnes <jbarnes@...tuousgeek.org>,
	John Linville <linville@...driver.com>,
	Andi Kleen <andi@...stfloor.org>,
	David Miller <davem@...emloft.net>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Ingo Molnar <mingo@...e.hu>, bcm43xx-dev@...ts.berlios.de,
	linux-wireless@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/3] Add API for weak DMA masks

On Thursday 01 May 2008 17:43:58 Christoph Hellwig wrote:
> On Thu, May 01, 2008 at 05:42:04PM +0200, Michael Buesch wrote:
> > Yeah. because it has to be done in every driver.
> > So we put the implementation into a central place, instead of
> > reimplementing the wheel over and over again. This way we avoid bugs,
> > like the "b43 broken on VIA boards" in the first place.
> > Currently every driver requesting a >32bit mask and not retrying with
> > a lower mask is broken on VIA hardware. I dunno how many of the current
> > drivers that are, but everybody can easily see that is not a b43-specific
> > problem that we should solve for b43 only.
> 
> Yeah.  Personally I'd rather let set_dma_mask fall back silently,

We've discussed that and this behaviour is not acceptable, as the driver
must know about a possible fallback in case it can do 32bit DMA
more efficiently than 64bit DMA, for example.

So here we go. People rejected that approach, that I also suggested.
Here's what people want.

-- 
Greetings Michael.
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