[PATCH] powerpc: Change archdata dma_data type to dma_addr_t

Becky Bruce beckyb at kernel.crashing.org
Thu Aug 27 06:20:56 EST 2009

On Aug 26, 2009, at 9:08 AM, Michael Ellerman wrote:

> On Wed, 2009-08-26 at 22:29 +1000, Benjamin Herrenschmidt wrote:
>> On Mon, 2009-08-24 at 21:48 +0200, Christoph Hellwig wrote:
>>> On Mon, Aug 24, 2009 at 11:17:14AM -0500, Becky Bruce wrote:
>>>> Previously, this was specified as a void *, but that's not
>>>> large enough on 32-bit systems with 36-bit physical
>>>> addressing support.  Change the type to dma_addr_t so it
>>>> will scale based on the size of a dma address.
>>> This looks extreml ugly to me.  It seems like the typical use is to
>>> store a pointer to a structure.  So what about making the direct
>>> dma case follow that general scheme instead?
>>> E.g. declare a
>>> struct direct_dma_data {
>>> 	dma_addr_t	direct_dma_offset;
>>> };
>>> and have one normal instace of it, and one per weird cell device.
>> Right, but we want to avoid a structure for the classic case of 32- 
>> bit
>> systems with no iommu...
>> I wouldn't mind doing a union here.
> That might be best, the patch as it stands is a horrible mess of  
> casts.

Let's be fair - the code before was a horrible mess of casts, I've  
just moved them :)

> Stashing a dma_addr_t into a void * is sort of gross, but storing a
> pointer to some struct (a void *) in a dma_addr_t is _really_ gross :)

Both are revolting (and storing a dma_addr_t into a void * is really  
gross when the void * is smaller than the dma_addr_t!!).  A union  
might not be a bad idea, though.  I'll look at doing that instead.


More information about the Linuxppc-dev mailing list