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Date: Wed, 19 Feb 2003 09:20:46 -0800
From: "Randy.Dunlap" <rddunlap@osdl.org>
To: Ion Badulescu <ionut@badula.org>
Cc: torvalds@transmeta.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] add new DMA_ADDR_T_SIZE define
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On Wed, 19 Feb 2003 11:26:27 -0500 (EST)
Ion Badulescu <ionut@badula.org> wrote:

| This patch adds a new preprocessor define called DMA_ADDR_T_SIZE for all 
| architectures, for the benefit of those drivers who care about its size 
| (and yes, starfire is one of them).
| 
| Alternatives are:
| 
| 1. a really ugly #ifdef in every single driver, which is error-prone and 
| likely to break (see drivers/net/starfire.c around line 274 and have a 
| barf bag ready).
| 
| 2. always cast it to u64, which adds unnecessary overhead to 32-bit 
| platforms.
| 
| 3. use run-time checks all over the place, of the 
| "sizeof(dma_addr_t)==sizeof(u64)" kind, which adds unnecessary overhead to 
| all platforms.
| 
| 4. use the results from pci_set_dma_mask(), which still amounts to 
| unnecessary run-time overhead on platforms which have a 32-bit dma_addr_t 
| to begin with.
| 
| So I think a define in each architecture's types.h file is the cleanest 
| way to approach this, and that's what my patch does.
| 
| Comments and/or suggestions are appreciated.
| -- 

Does this help with being able to printk() a <dma_addr_t>?  How?
Always use a cast to (u64) or something else?

--
~Randy
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