Re: + kmap_types-make-most-arches-use-generic-header-file.patch added to -mm tree

[Randy Dunlap <randy.dunlap@oracle.com>]

Arnd Bergmann wrote:
> On Thursday 28 May 2009 21:31:06 akpm@linux-foundation.org wrote:
>> The patch titled
>>      kmap_types: make most arches use generic header file
>> has been added to the -mm tree.  Its filename is
>>      kmap_types-make-most-arches-use-generic-header-file.patch
> 
> Thanks for adding it back.
> 
>> Move the KM_FENCE_ macro additions into asm-generic/kmap_types.h,
>> controlled by __WITH_KM_FENCE from each arch's kmap_types.h file.
> 
> I completely missed this part of the patch before. Is this actually useful?
> All architectures that define it (x86 with a twist, the check for X86_32 is
> an artifact from the x86 arch merge) do
> 
> #ifdef CONFIG_DEBUG_HIGHMEM
> #define  __WITH_KM_FENCE
> #endif
> 
> However: alpha, ia64, m32r, parisc and sh don't even support CONFIG_HIGHMEM
> and therefore also can't set CONFIG_DEBUG_HIGHMEM. Conversely, mn10300 and
> sparc can set CONFIG_DEBUG_HIGHMEM but don't get the extra checking
> from KM_FENCE without this.
> 
> It seems to me that it would be at least as correct but simpler to just
> leave the check for CONFIG_DEBUG_HIGHMEM.

Yes, I noticed that's how it was in your patch.
 
>> Would be nice to be able to add custom KM_types per arch, but I don't yet
>> see a nice, clean way to do that.
> 
> FWIW, the only types that are not in the generic file right now are
> 
> arm: KM_L2_CACHE
> powerpc: KM_PPC_SYNC_ICACHE, KM_PPC_SYNC_PAGE
> um: KM_UML_USERCOPY
> 
> We could easily add these as KM_SYNC_ICACHE, KM_SYNC_DCACHE and
> KM_UML_USERCOPY in the generic file and get rid of all architecture
> specific types here.

OK by me.  I'll update it...

Thanks for looking.

-- 
~Randy
LPC 2009, Sept. 23-25, Portland, Oregon
http://linuxplumbersconf.org/2009/