Re: [PATCH 4/7] swiotlb: Allow arch override of address_needs_mapping

[Jeremy Fitzhardinge <jeremy@goop.org>]

FUJITA Tomonori wrote:
>> Some architectures need non-trivial bus<->phys conversion routines, etc, 
>>     
>
> Only Xen needs such conversion for swiotlb.
>   

Becky's patches of last week also added __weak annotations to 
swiotlb_bus_to_virt, virt_to_bus and bus_to_phys; added the hwdev 
parameter to swiotlb_bus_to_phys; and added a weak 
swiotlb_arch_address_needs_mapping.  I assume that was needed because 
powerpc needs non-trivial implementations for those functions.

>> so either we can require it that all architectures wishing to use 
>> swiotlb define these functions, or have weak default functions that can 
>> be overridden by architectures where necessary.
>>     
>
> Can you give an example? I don't think IA64, X86_64 or POWER (which
> will use swiotlb) need any __weak functions. If you say other archs
> could use swiotlb, please tell me how they need these __weak.
>   

As I said, Becky's patches added hooks in many of the places we added 
them for Xen.  I assume that's because powerpc needs them; I have not 
seen the arch/powerpc side of those changes.

    J