linux-kernel - Use resource_size_t for serial MMIO addresses

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Date:	Tue, 20 Feb 2007 14:17:17 +1100
From:	David Gibson <david@...son.dropbear.id.au>
To:	Andrew Morton <akpm@...l.org>
Cc:	Russell King <rmk@....linux.org.uk>, linux-kernel@...r.kernel.org,
	linuxppc-dev@...abs.org
Subject: Use resource_size_t for serial MMIO addresses

Andrew, please apply to -mm.  I think these should be good to merge
for 2.6.22.

At present, MMIO addresses for serial port (the ->mapbase field in
uart_port and other structures) are unsigned longs.  This causes
problems on some 32-bit platforms which have a >32-bit physical
address bus, for example the embedded PowerPC 440GP chip, which has a
36-bit physical address bus, and on-chip serial ports located at an
MMIO address above 4GB.

The second patch in this series changes mapbase to a resource_size_t
(which can be 64-bit on the problematic platforms) in struct uart_port
and struct plat_serial8250_port.  It does *not* change the type in
serial_struct, because that structure is exposed to userspace.  It is
therefore unsafe to use setserial to change the address parameters on
a port using a mapbase above 4GB.

The first patch in the series contains the damage of the setserial
problem.  It allows serial ports to be marked with a new
UPF_FIXED_PORT flag, which causes any attempts to change the port's
type (PIO/MMIO etc.), address or irq with setserial to be ignored.
While using setserial to alter the port address is useful for legacy
ISA ports, it is generally a bad idea for ports such as on-chip or
other hardwired ports where the arch code has good information (from
firmware or hardware probing) on the port's type and address.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson
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