[PATCH 02/10] isa: Implement the max_num_isa_dev macro

[William Breathitt Gray <vilhelm.gray@gmail.com>]

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>
---
 include/linux/isa.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/include/linux/isa.h b/include/linux/isa.h
index d410259..bc0a7c0 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 */
-- 
2.7.3