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authorWilliam Breathitt Gray <vilhelm.gray@gmail.com>2016-05-01 18:43:10 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-05-02 09:32:04 -0700
commitd9a9c6172d1cec51851e9015b6c4379635c31f1a (patch)
treeb30d1e4e703e43daa93644c16141c1816ef9f1b5 /include/linux/isa.h
parent339e6e31d2bfb40354cbfe672b357b88a88223f2 (diff)
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>
Diffstat (limited to 'include/linux/isa.h')
-rw-r--r--include/linux/isa.h11
1 files changed, 11 insertions, 0 deletions
diff --git a/include/linux/isa.h b/include/linux/isa.h
index e394917d18c2..5ab85281230b 100644
--- a/include/linux/isa.h
+++ b/include/linux/isa.h
@@ -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 */