linux-kernel - Re: [PATCH] cciss: change Cmd_sg_list.sg_chain_dma type to dma_addr

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Message-ID: <20091123083333.GU8742@kernel.dk>
Date:	Mon, 23 Nov 2009 09:33:33 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Alex Chiang <achiang@...com>
Cc:	Don Brace <brace@...rdog.cce.hp.com>,
	"Stephen M. Cameron" <scameron@...rdog.cce.hp.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cciss: change Cmd_sg_list.sg_chain_dma type to
	dma_addr_t

On Tue, Nov 17 2009, Alex Chiang wrote:
> A recent commit broke the ia64 build:
> 
> 	Author: Don Brace <brace@...rdog.cce.hp.com>
> 	Date:   Thu Nov 12 12:50:01 2009 -0600
> 
> 	cciss: Add enhanced scatter-gather support.
> 
> because of this hunk:
> 
> 	--- a/drivers/block/cciss.h
> 	+++ b/drivers/block/cciss.h
> 	+struct Cmd_sg_list {
> 	+       SGDescriptor_struct     *sgchain;
> 	+       dma64_addr_t            sg_chain_dma;
> 	+       int                     chain_block_size;
> 	+};
> 
> The issue is that dma64_addr_t isn't #define'd on ia64.
> 
> The way that we're using Cmd_sg_list.sg_chain_dma is to hold an
> address returned from pci_map_single().
> 
> 	+               temp64.val = pci_map_single(h->pdev,
> 	+                                 h->cmd_sg_list[c->cmdindex]->sgchain,
> 	+                                 len, dir);
> 	+
> 	+               h->cmd_sg_list[c->cmdindex]->sg_chain_dma = temp64.val;
> 
> pci_map_single() returns a dma_addr_t too.
> 
> This code will still work even on a 32-bit x86 build, where
> dma_addr_t is defined to be a u32 because it will simply be
> promoted to the __u64 that temp64.val is defined as.
> 
> Thus, declaring Cmd_sg_list.sg_chain_dma as dma_addr_t is safe.

Applied for 2.6.32.

-- 
Jens Axboe

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