Commit 04a536bf authored by Miles Chen's avatar Miles Chen Committed by Linus Torvalds
Browse files

include/linux/gfp.h: further document GFP_DMA32 

kmalloc(..., GFP_DMA32) does not return DMA32 memory because the DMA32
kmalloc cache array is not implemented.  (Reason: there is no such user
in kernel).

Put a short comment about this so people can understand this by reading
the comment.

[1] https://lists.linuxfoundation.org/pipermail/iommu/2018-December/031696.html

Link: https://lkml.kernel.org/r/20211207093610.6406-1-miles.chen@mediatek.com


Signed-off-by: default avatarMiles Chen <miles.chen@mediatek.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent be1a13eb

include/linux/gfp.h

+3 −1
Original line number Original line Diff line number Diff line
@@ -302,7 +302,9 @@ struct vm_area_struct; 
 * lowest zone as a type of emergency reserve.

 * lowest zone as a type of emergency reserve.

 *

 *

 * %GFP_DMA32 is similar to %GFP_DMA except that the caller requires a 32-bit

 * %GFP_DMA32 is similar to %GFP_DMA except that the caller requires a 32-bit

 * address.

 * address. Note that kmalloc(..., GFP_DMA32) does not return DMA32 memory

 * because the DMA32 kmalloc cache array is not implemented.

 * (Reason: there is no such user in kernel).

 *

 *

 * %GFP_HIGHUSER is for userspace allocations that may be mapped to userspace,

 * %GFP_HIGHUSER is for userspace allocations that may be mapped to userspace,

 * do not need to be directly accessible by the kernel but that cannot

 * do not need to be directly accessible by the kernel but that cannot