From: Miles Chen <miles.chen@xxxxxxxxxxxx> Subject: 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@xxxxxxxxxxxx Signed-off-by: Miles Chen <miles.chen@xxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/gfp.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/include/linux/gfp.h~gfp-further-document-gfp_dma32 +++ a/include/linux/gfp.h @@ -302,7 +302,9 @@ struct vm_area_struct; * lowest zone as a type of emergency reserve. * * %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, * do not need to be directly accessible by the kernel but that cannot _
