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hwmon: (pmbus) More stringent checking of VOUT_MODE register

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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>
This commit is contained in:
Guenter Roeck 2011-03-01 13:49:18 -08:00
parent a3eeb45353
commit 83274c68a3
1 changed files with 4 additions and 3 deletions
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7
drivers/hwmon/pmbus_core.c
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@ -1426,10 +1426,11 @@ static void pmbus_find_attributes(struct i2c_client *client,
static int pmbus_identify_common(struct i2c_client *client,
struct pmbus_data *data)
{
int vout_mode, exponent;
int vout_mode = -1, exponent;
vout_mode = pmbus_read_byte_data(client, 0, PMBUS_VOUT_MODE);
if (vout_mode >= 0) {
if (pmbus_check_byte_register(client, 0, PMBUS_VOUT_MODE))
vout_mode = pmbus_read_byte_data(client, 0, PMBUS_VOUT_MODE);
if (vout_mode >= 0 && vout_mode != 0xff) {
/*
* Not all chips support the VOUT_MODE command,
* so a failure to read it is not an error.