Hi Jean,
On Sun, Aug 28, 2011 at 09:01:44AM -0400, Jean Delvare wrote:
> Hi Guenter,
>
> On Fri, 26 Aug 2011 09:19:02 -0700, Guenter Roeck wrote:
> > Return values for functions reading/writing manufacturer specific registers are
> > poorly explained. Add comments to improve documentation.
> >
> > Signed-off-by: Guenter Roeck <guenter.roeck@xxxxxxxxxxxx>
> > ---
> > drivers/hwmon/pmbus/pmbus.h | 18 ++++++++++++++++--
> > 1 files changed, 16 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
> > index a6ae20f..da90167 100644
> > --- a/drivers/hwmon/pmbus/pmbus.h
> > +++ b/drivers/hwmon/pmbus/pmbus.h
> > @@ -134,8 +134,16 @@
> > * Semantics:
> > * Virtual registers are all word size.
> > * READ registers are read-only; writes are either ignored or return an error.
> > - * RESET registers are read/write. Reading returns zero (used for detection),
> > - * writing any value causes the associated history to be reset.
> > + * RESET registers are read/write. Reading reset registers returns zero
> > + * (used for detection), writing any value causes the associated history to be
> > + * reset.
> > + * Virtual registers have to be handled in device specific driver code. Chip
> > + * driver code returns non-negative register values if a virtual register is
> > + * supported, or a negative error code if not. The chip driver may return
> > + * -ENODATA or any other error code in this case, though an error code other
> > + * than -ENODATA is handled more efficiently and thus preferred. Either case,
> > + * the calling PMBus core code will abort if the chip driver returns an error
> > + * code when reading or writing virtual registers.
>
> The explanation below suggests that the code doesn't actually abort in
> the -ENODATA case, but instead falls back to an alternative register
> access?
>
Correct, except if -ENODATA is returned for virtual registers.
I'll add some more text to the documentation to describe how the access works
in more detail.
> > */
> > #define PMBUS_VIRT_BASE 0x100
> > #define PMBUS_VIRT_READ_TEMP_MIN (PMBUS_VIRT_BASE + 0)
> > @@ -320,6 +328,12 @@ struct pmbus_driver_info {
> > * The following functions map manufacturing specific register values
> > * to PMBus standard register values. Specify only if mapping is
> > * necessary.
> > + * Function return the register value (read) or zero (write) if
>
> "Functions return" or "Function returns".
>
Functions return
> > + * successful. A return value of -ENODATA indicates that there is no
> > + * manufacturer specific register, but that a standard PMBus register
> > + * may exist. Any other negative return value indicates that the
> > + * register does not exist, and that no attempt should be made to read
> > + * the standard register.
> > */
> > int (*read_byte_data)(struct i2c_client *client, int page, int reg);
> > int (*read_word_data)(struct i2c_client *client, int page, int reg);
>
> Other than this, looks good, thanks for adding this piece of
> documentation.
>
> Acked-by: Jean Delvare <khali@xxxxxxxxxxxx>
>
Thanks a lot for the review!
Guenter
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