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lib: add iomem emulation (logic_iomem)

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Add IO memory emulation that uses callbacks for read/write to
the allocated regions. The callbacks can be registered by the
users using logic_iomem_alloc().

To use, an architecture must 'select LOGIC_IOMEM' in Kconfig
and then include <asm-generic/logic_io.h> into asm/io.h to get
the __raw_read*/__raw_write* functions.

Optionally, an architecture may 'select LOGIC_IOMEM_FALLBACK'
in which case non-emulated regions will 'fall back' to the
various real_* functions that must then be provided.

Cc: Arnd Bergmann <arnd@kernel.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
This commit is contained in:
Johannes Berg 2021-03-05 13:19:52 +01:00 • committed by Richard Weinberger
parent 0bbadafdc4
commit ca2e334232
5 changed files with 474 additions and 0 deletions
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14
lib/Kconfig
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@ -102,6 +102,20 @@ config INDIRECT_PIO
When in doubt, say N.
config INDIRECT_IOMEM
bool
help
This is selected by other options/architectures to provide the
emulated iomem accessors.
config INDIRECT_IOMEM_FALLBACK
bool
depends on INDIRECT_IOMEM
help
If INDIRECT_IOMEM is selected, this enables falling back to plain
mmio accesses when the IO memory address is not a registered
emulated region.
config CRC_CCITT
tristate "CRC-CCITT functions"
help