Re: [lm-sensors] [PATCH 3/4] hwmon: (pmbus) Improve fan detection

[Guenter Roeck <guenter.roeck@ericsson.com>]

Hi Jean,

On Sun, Jul 03, 2011 at 04:14:32AM -0400, Jean Delvare wrote:
> Hi Guenter,
> 
> On Thu, 30 Jun 2011 10:29:52 -0700, Guenter Roeck wrote:
> > Some PMBus devices return no error when reading fan speed registers, but don't
> > really support fans. Strengthen fan detection by also checking if fan
> > configuration registers exist.
> > 
> > Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
> > ---
> >  drivers/hwmon/pmbus.c |    6 ++++--
> >  1 files changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/hwmon/pmbus.c b/drivers/hwmon/pmbus.c
> > index 98e2e28..b0ea00b 100644
> > --- a/drivers/hwmon/pmbus.c
> > +++ b/drivers/hwmon/pmbus.c
> > @@ -47,12 +47,14 @@ static void pmbus_find_sensor_groups(struct i2c_client *client,
> >  	if (info->func[0]
> >  	    && pmbus_check_byte_register(client, 0, PMBUS_STATUS_INPUT))
> >  		info->func[0] |= PMBUS_HAVE_STATUS_INPUT;
> > -	if (pmbus_check_word_register(client, 0, PMBUS_READ_FAN_SPEED_1)) {
> > +	if (pmbus_check_byte_register(client, 0, PMBUS_FAN_CONFIG_12) &&
> > +	    pmbus_check_word_register(client, 0, PMBUS_READ_FAN_SPEED_1)) {
> >  		info->func[0] |= PMBUS_HAVE_FAN12;
> >  		if (pmbus_check_byte_register(client, 0, PMBUS_STATUS_FAN_12))
> >  			info->func[0] |= PMBUS_HAVE_STATUS_FAN12;
> >  	}
> > -	if (pmbus_check_word_register(client, 0, PMBUS_READ_FAN_SPEED_3)) {
> > +	if (pmbus_check_byte_register(client, 0, PMBUS_FAN_CONFIG_34) &&
> > +	    pmbus_check_word_register(client, 0, PMBUS_READ_FAN_SPEED_3)) {
> >  		info->func[0] |= PMBUS_HAVE_FAN34;
> >  		if (pmbus_check_byte_register(client, 0, PMBUS_STATUS_FAN_34))
> >  			info->func[0] |= PMBUS_HAVE_STATUS_FAN34;
> 
> Then wouldn't it be sufficient to only test PMBUS_FAN_CONFIG_12 and
> PMBUS_FAN_CONFIG_34, respectively? This would make the function
> somewhat faster.

I'd rather keep both. Devices should not return a valid value or should at least set 
the command error flag in the status register if they don't support fans and the fan speed
register is read. If I can't trust that (and I can't because Intersil devices do just that),
I can not trust the configuration register either. 

Thanks,
Guenter

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