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	Tue, 10 Jun 2008 10:23:59 -0400
From: Michael Buesch <mb@bu3sch.de>
To: "Miles Lane" <miles.lane@gmail.com>
Subject: Re: BUG: NULL pointer dereference at 00000000 -- IP: [<f8e783d5>] :b43:b43_dma_mapping_error+0x16/0x155
Date: Tue, 10 Jun 2008 16:23:33 +0200
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On Tuesday 10 June 2008 16:09:37 Miles Lane wrote:
> BUG: unable to handle kernel NULL pointer dereference at 00000000
> IP: [<f8e783d5>] :b43:b43_dma_mapping_error+0x16/0x155


It seems to crash at
 60 extern const struct dma_mapping_ops *dma_ops;
 61 
 62 static inline int dma_mapping_error(dma_addr_t dma_addr)
 63 {
 64         if (dma_ops->mapping_error)
 65                 return dma_ops->mapping_error(dma_addr);
 66 
 67         return (dma_addr == bad_dma_address);
 68 }

because dma_ops is a NULL pointer here.
Can you add a WARN_ON(!dma_ops); at the beginning of the function
inside of include/asm/x86/dma-mapping.h to confirm this?

-- 
Greetings Michael.