This patch adds default 64-bit mathematics in aclinux.h using do_div(). As
do_div() can be used for all Linux architectures, this can also be used as
stub macros for ACPICA 64-bit mathematics.
These macros are required by drivers/acpi/utmath.c when ACPI_USE_NATIVE_DIVIDE
is not defined. It is used by ACPICA, so currently this is only meaningful to
CONFIG_ACPI builds. So the kernel will not use these macros unless CONFIG_ACPI
is defined and ACPI_USE_DIVIDE is not defined.
For 64-bit kernels:
In include/acpi/actypes.h, for ACPI_MACHINE_WIDTH=64,
ACPI_USE_NATIVE_DIVIDE will be defined, thus these macros are not used.
In include/acpi/platform/aclinux.h, for __KERNEL__ surrounded code,
ACPI_MACHINE_WIDTH is defined to be BITS_PER_LONG.
So all 64-bit kernels do not use these macros.
For 32-bit kernels:
As mentioned above, these macros will be used when BITS_PER_LONG is 32.
Thus currently the i328 kernels are the only users for these macros.
But they won't use this default implementation provided by this patch,
because in arch/x86/include/asm/acenv.h, there are already overrides
implemented. So these default macros are not used by 32-bit x86 (i386)
kernels.
These macros will only be used by future non x86 32-bit architectures
that try to support ACPI in Linux kernel.
During the period they do not have arch specific implementations of such
macros, we can avoid build errors for them.
And since they can see ACPICA functioning without implementing any arch
specific environment tunings, we can also avoid function errors for
them.
As this implementation is not performance friendly, those architectures
still need to implement real support in the end.
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
[rjw: Changelog]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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