Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 2fd74e25 authored by FUJITA Tomonori's avatar FUJITA Tomonori Committed by Linus Torvalds
Browse files

Documentation/DMA-API-HOWTO: add ARCH_KMALLOC_MINALIGN description 



Add ARCH_KMALLOC_MINALIGN description in "Platform Issues" section.

Signed-off-by: default avatarFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Matt Mackall <mpm@selenic.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4ae9ca82

Documentation/DMA-API-HOWTO.txt

+14 −1
Original line number Diff line number Diff line
@@ -738,7 +738,20 @@ to "Closing". 
   CONFIG_NEED_SG_DMA_LENGTH if the architecture supports IOMMUs

   (including software IOMMU).



2) More to come...

2) ARCH_KMALLOC_MINALIGN



   Architectures must ensure that kmalloc'ed buffer is

   DMA-safe. Drivers and subsystems depend on it. If an architecture

   isn't fully DMA-coherent (i.e. hardware doesn't ensure that data in

   the CPU cache is identical to data in main memory),

   ARCH_KMALLOC_MINALIGN must be set so that the memory allocator

   makes sure that kmalloc'ed buffer doesn't share a cache line with

   the others. See arch/arm/include/asm/cache.h as an example.



   Note that ARCH_KMALLOC_MINALIGN is about DMA memory alignment

   constraints. You don't need to worry about the architecture data

   alignment constraints (e.g. the alignment constraints about 64-bit

   objects).



			   Closing