On Sun, 3 Jul 2011 09:27:46 -0700, Guenter Roeck wrote:
> 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@xxxxxxxxxxxx>
> > > ---
> > > 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.
I think that what worries me is the asymmetry. Is it not possible for a
device to have FAN_SPEED_2 and not FAN_SPEED_1? If not then your code
is fine, I agree. But if it is possible, then we need smarter code.
But also note that I don't know a thing about PMBus, so there may be
nothing to worry about.
--
Jean Delvare
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