Re: [PATCH] hwmon: (pmbus) Improve initialization of 'currpage' and 'currphase'

[Guenter Roeck <linux@roeck-us.net>]

On Thu, May 07, 2020 at 01:19:58PM -0700, Alex Qiu wrote:
> Hi Guenter,
> 
> LGTM; minor nits:
> 
> On Thu, May 7, 2020 at 10:44 AM Guenter Roeck <linux@roeck-us.net> wrote:
> >
> > The 'currpage' and 'currphase' variables in struct pmbus_data are used by
> > the PMBus core to determine if the phase or page value has changed. Both
> > are initialized with values which are never expected to be set in the code
> > to ensure that the first page/phase write operation is actually performed.
> >
> > This is not well explained and occasionally causes confusion. Change the
> > type of both variables to s16 and initialize with -1 to ensure that the
> > initial value never matches a requested value, and clarify that this
> > value means "unknown/unset".
> >
> > Cc: Alex Qiu <xqiu@google.com>
> > Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> > ---
> >  drivers/hwmon/pmbus/pmbus_core.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
> > index 8d321bf7d15b..a420877ba533 100644
> > --- a/drivers/hwmon/pmbus/pmbus_core.c
> > +++ b/drivers/hwmon/pmbus/pmbus_core.c
> > @@ -109,8 +109,8 @@ struct pmbus_data {
> >         bool has_status_word;           /* device uses STATUS_WORD register */
> >         int (*read_status)(struct i2c_client *client, int page);
> >
> > -       u8 currpage;
> > -       u8 currphase;   /* current phase, 0xff for all */
> > +       s16 currpage;   /* current page, -1 for unknown/unset */
> > +       s16 currphase;  /* current phase, 0xff for all, -1 for unknown/unset */
> I'm not sure if assigning macros for -1 and 0xff would be a good idea?

The driver uses hardcoded 0xff in various places. We could replace it
with defines, but that should be a separate patch.

Thanks,
Guenter