linux-kernel - Re: bnx2 fails to compile on parisc because of missing get_dma

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Message-Id: <20100617210539V.fujita.tomonori@lab.ntt.co.jp>
Date:	Thu, 17 Jun 2010 21:13:43 +0900
From:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To:	davem@...emloft.net
Cc:	JBottomley@...ell.com, netdev@...r.kernel.org,
	linux-parisc@...r.kernel.org, linux-kernel@...r.kernel.org,
	fujita.tomonori@....ntt.co.jp, mchan@...adcom.com
Subject: Re: bnx2 fails to compile on parisc because of missing
 get_dma_ops()

On Wed, 16 Jun 2010 18:16:32 -0700 (PDT)
David Miller <davem@...emloft.net> wrote:

> From: James Bottomley <JBottomley@...ell.com>
> Date: Wed, 16 Jun 2010 20:13:49 -0500
> 
> > However, this code in bnx2.c:
> > 
> > 		if (!get_dma_ops(&pdev->dev)->sync_single_for_cpu) {
> > 			next_rx_buf =
> > 				&rxr->rx_buf_ring[
> > 					RX_RING_IDX(NEXT_RX_BD(sw_cons))];
> > 			prefetch(next_rx_buf->desc);
> > 		}
> > 
> > Looks remarkably fragile: what exactly is it trying to do?
> > 
> > The commit that causes the problem:
> > 
> > commit a33fa66bcf365ffe5b79d1ae1d3582cc261ae56e
> > Author: Michael Chan <mchan@...adcom.com>
> > Date:   Thu May 6 08:58:13 2010 +0000
> > 
> >     bnx2: Add prefetches to rx path.
> > 
> > Looks fairly innocuous by the description.
> > 
> > Should parisc have a get_dma_ops()?  We don't need one because our dma
> > ops are per platform not per bus.
> 
> I think asking for get_dma_ops() directly in a driver is dodgy at
> best, especially one that is meant to compile on any PCI supporting
> system.  At least right now.

Yeah, it should be used only in the architecture core
code. get_dma_ops() is not mentioned in DMA-API-* docs.
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