Why does PIC1 use io 0x0020 to 0x002F?

David Campbell (campbell@gear.torque.net)
Fri, 3 Apr 1998 07:10:16 +0000

I am trying to write a kernel driver which "manipulates" the config
registers of a National Semiconductor super-io chipset (config registers
are located at 0x002e-0x002f).

I notice that linux/arch/i386/irq.c reserves the io port range of 0x0020
to 0x002f. All the information I have indicates that the programable
interupt controller only uses two io ports (0x0020 and 0x0021).

Does anyone know what the correct io port span for PIC1 should be?
Would it be possible to reduce the io port span of PIC1 from 16 ports wide
to less than 15 (so I can "legally" access 0x002e and 0x002f).

David Campbell

PS: Please email responses directly to me.
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campbell@torque.net (Parallel port device related mail)
dcampbel@p01.as17.honeywell.com.au (For all other mail)

"All parallel ports are equal - Some are more equal than others"

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