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isa: Implement the max_num_isa_dev macro 

max_num_isa_dev is a macro to determine the maximum possible number of
ISA devices which may be registered in the I/O port address space given
the address extent of the ISA devices.

The highest base address possible for an ISA device is 0x3FF; this
results in 1024 possible base addresses. Dividing the number of possible
base addresses by the address extent taken by each device results in the
maximum number of devices on a system.

Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
William Breathitt Gray 2016-05-01 18:43:10 -04:00 committed by Greg Kroah-Hartman
parent 339e6e31d2
commit d9a9c6172d
1 changed files with 11 additions and 0 deletions
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11
include/linux/isa.h
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@ -57,4 +57,15 @@ static void __exit __isa_driver##_exit(void) \
} \
module_exit(__isa_driver##_exit);
/**
* max_num_isa_dev() - Maximum possible number registered of an ISA device
* @__ida_dev_ext: ISA device address extent
*
* The highest base address possible for an ISA device is 0x3FF; this results in
* 1024 possible base addresses. Dividing the number of possible base addresses
* by the address extent taken by each device results in the maximum number of
* devices on a system.
*/
#define max_num_isa_dev(__isa_dev_ext) (1024 / __isa_dev_ext)
#endif /* __LINUX_ISA_H */