From 83274c68a34094bbb465589e61f91a3714f8d026 Mon Sep 17 00:00:00 2001
From: Guenter Roeck <guenter.roeck@ericsson.com>
Date: Tue, 1 Mar 2011 13:49:18 -0800
Subject: [PATCH] hwmon: (pmbus) More stringent checking of VOUT_MODE register

Some PMBus chips do not support the VOUT_MODE register. To make matters worse,
such chips may not return an error when reading the register either, but instead
return 0xff.

Check if the register exists using pmbus_check_byte_register() before reading
its value. In addition, validate the returned value and ignore it if it is 0xff
(which is invalid).

Reported-by: Greg Schnorr <gschnorr@cisco.com>
Tested-by: Greg Schnorr <gschnorr@cisco.com>
Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
Acked-by: Greg Schnorr <gschnorr@cisco.com>
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