Orange Pi5 kernel

^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   1) # SPDX-License-Identifier: GPL-2.0-only
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   2) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   3) config NO_DMA
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   4) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   5) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   6) config HAS_DMA
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   7) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   8) 	depends on !NO_DMA
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300   9) 	default y
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  10) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  11) config DMA_OPS
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  12) 	depends on HAS_DMA
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  13) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  14) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  15) #
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  16) # IOMMU drivers that can bypass the IOMMU code and optionally use the direct
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  17) # mapping fast path should select this option and set the dma_ops_bypass
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  18) # flag in struct device where applicable
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  19) #
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  20) config DMA_OPS_BYPASS
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  21) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  22) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  23) config NEED_SG_DMA_LENGTH
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  24) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  25) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  26) config NEED_DMA_MAP_STATE
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  27) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  28) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  29) config ARCH_DMA_ADDR_T_64BIT
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  30) 	def_bool 64BIT || PHYS_ADDR_T_64BIT
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  31) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  32) config ARCH_HAS_DMA_COHERENCE_H
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  33) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  34) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  35) config ARCH_HAS_DMA_SET_MASK
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  36) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  37) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  38) #
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  39) # Select this option if the architecture needs special handling for
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  40) # DMA_ATTR_WRITE_COMBINE.  Normally the "uncached" mapping should be what
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  41) # people thing of when saying write combine, so very few platforms should
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  42) # need to enable this.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  43) #
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  44) config ARCH_HAS_DMA_WRITE_COMBINE
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  45) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  46) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  47) #
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  48) # Select if the architectures provides the arch_dma_mark_clean hook
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  49) #
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  50) config ARCH_HAS_DMA_MARK_CLEAN
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  51) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  52) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  53) config DMA_DECLARE_COHERENT
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  54) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  55) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  56) config ARCH_HAS_SETUP_DMA_OPS
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  57) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  58) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  59) config ARCH_HAS_TEARDOWN_DMA_OPS
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  60) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  61) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  62) config ARCH_HAS_SYNC_DMA_FOR_DEVICE
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  63) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  64) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  65) config ARCH_HAS_SYNC_DMA_FOR_CPU
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  66) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  67) 	select NEED_DMA_MAP_STATE
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  68) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  69) config ARCH_HAS_SYNC_DMA_FOR_CPU_ALL
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  70) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  71) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  72) config ARCH_HAS_DMA_PREP_COHERENT
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  73) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  74) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  75) config ARCH_HAS_FORCE_DMA_UNENCRYPTED
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  76) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  77) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  78) config DMA_VIRT_OPS
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  79) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  80) 	depends on HAS_DMA
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  81) 	select DMA_OPS
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  82) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  83) config SWIOTLB
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  84) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  85) 	select NEED_DMA_MAP_STATE
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  86) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  87) #
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  88) # Should be selected if we can mmap non-coherent mappings to userspace.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  89) # The only thing that is really required is a way to set an uncached bit
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  90) # in the pagetables
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  91) #
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  92) config DMA_NONCOHERENT_MMAP
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  93) 	default y if !MMU
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  94) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  95) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  96) config DMA_COHERENT_POOL
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  97) 	select GENERIC_ALLOCATOR
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  98) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300  99) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100) config DMA_REMAP
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102) 	depends on MMU
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103) 	select DMA_NONCOHERENT_MMAP
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105) config DMA_DIRECT_REMAP
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106) 	bool
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107) 	select DMA_REMAP
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108) 	select DMA_COHERENT_POOL
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 109) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 110) config DMA_CMA
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 111) 	bool "DMA Contiguous Memory Allocator"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 112) 	depends on HAVE_DMA_CONTIGUOUS && CMA
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 113) 	help
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 114) 	  This enables the Contiguous Memory Allocator which allows drivers
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 115) 	  to allocate big physically-contiguous blocks of memory for use with
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 116) 	  hardware components that do not support I/O map nor scatter-gather.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 117) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 118) 	  You can disable CMA by specifying "cma=0" on the kernel's command
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 119) 	  line.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 120) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 121) 	  For more information see <kernel/dma/contiguous.c>.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 122) 	  If unsure, say "n".
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 123) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 124) if  DMA_CMA
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 125) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 126) config DMA_PERNUMA_CMA
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 127) 	bool "Enable separate DMA Contiguous Memory Area for each NUMA Node"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 128) 	default NUMA && ARM64
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 129) 	help
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 130) 	  Enable this option to get pernuma CMA areas so that devices like
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 131) 	  ARM64 SMMU can get local memory by DMA coherent APIs.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 132) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 133) 	  You can set the size of pernuma CMA by specifying "cma_pernuma=size"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 134) 	  on the kernel's command line.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 135) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 136) comment "Default contiguous memory area size:"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 137) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 138) config CMA_SIZE_MBYTES
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 139) 	int "Size in Mega Bytes"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 140) 	depends on !CMA_SIZE_SEL_PERCENTAGE
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 141) 	default 0 if X86
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 142) 	default 16
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 143) 	help
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 144) 	  Defines the size (in MiB) of the default memory area for Contiguous
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 145) 	  Memory Allocator.  If the size of 0 is selected, CMA is disabled by
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 146) 	  default, but it can be enabled by passing cma=size[MG] to the kernel.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 147) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 148) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 149) config CMA_SIZE_PERCENTAGE
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 150) 	int "Percentage of total memory"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 151) 	depends on !CMA_SIZE_SEL_MBYTES
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 152) 	default 0 if X86
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 153) 	default 10
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 154) 	help
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 155) 	  Defines the size of the default memory area for Contiguous Memory
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 156) 	  Allocator as a percentage of the total memory in the system.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 157) 	  If 0 percent is selected, CMA is disabled by default, but it can be
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 158) 	  enabled by passing cma=size[MG] to the kernel.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 159) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 160) choice
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 161) 	prompt "Selected region size"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 162) 	default CMA_SIZE_SEL_MBYTES
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 163) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 164) config CMA_SIZE_SEL_MBYTES
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 165) 	bool "Use mega bytes value only"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 166) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 167) config CMA_SIZE_SEL_PERCENTAGE
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 168) 	bool "Use percentage value only"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 169) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 170) config CMA_SIZE_SEL_MIN
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 171) 	bool "Use lower value (minimum)"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 172) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 173) config CMA_SIZE_SEL_MAX
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 174) 	bool "Use higher value (maximum)"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 175) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 176) endchoice
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 177) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 178) config CMA_ALIGNMENT
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 179) 	int "Maximum PAGE_SIZE order of alignment for contiguous buffers"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 180) 	range 2 12
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 181) 	default 8
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 182) 	help
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 183) 	  DMA mapping framework by default aligns all buffers to the smallest
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 184) 	  PAGE_SIZE order which is greater than or equal to the requested buffer
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 185) 	  size. This works well for buffers up to a few hundreds kilobytes, but
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 186) 	  for larger buffers it just a memory waste. With this parameter you can
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 187) 	  specify the maximum PAGE_SIZE order for contiguous buffers. Larger
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 188) 	  buffers will be aligned only to this specified order. The order is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 189) 	  expressed as a power of two multiplied by the PAGE_SIZE.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 190) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 191) 	  For example, if your system defaults to 4KiB pages, the order value
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 192) 	  of 8 means that the buffers will be aligned up to 1MiB only.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 193) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 194) 	  If unsure, leave the default value "8".
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 195) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 196) endif
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 197) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 198) config DMA_API_DEBUG
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 199) 	bool "Enable debugging of DMA-API usage"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 200) 	select NEED_DMA_MAP_STATE
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 201) 	help
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 202) 	  Enable this option to debug the use of the DMA API by device drivers.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 203) 	  With this option you will be able to detect common bugs in device
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 204) 	  drivers like double-freeing of DMA mappings or freeing mappings that
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 205) 	  were never allocated.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 206) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 207) 	  This option causes a performance degradation.  Use only if you want to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 208) 	  debug device drivers and dma interactions.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 209) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 210) 	  If unsure, say N.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 211) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 212) config DMA_API_DEBUG_SG
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 213) 	bool "Debug DMA scatter-gather usage"
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 214) 	default y
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 215) 	depends on DMA_API_DEBUG
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 216) 	help
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 217) 	  Perform extra checking that callers of dma_map_sg() have respected the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 218) 	  appropriate segment length/boundary limits for the given device when
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 219) 	  preparing DMA scatterlists.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 220) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 221) 	  This is particularly likely to have been overlooked in cases where the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 222) 	  dma_map_sg() API is used for general bulk mapping of pages rather than
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 223) 	  preparing literal scatter-gather descriptors, where there is a risk of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 224) 	  unexpected behaviour from DMA API implementations if the scatterlist
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 225) 	  is technically out-of-spec.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 226) 
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 227) 	  If unsure, say N.