Re: [PATCH v2 1/1] mux: consumer: Add dummy functions for !CONFIG_MULTIPLEXER case

[Kuppuswamy, Sathyanarayanan]

Hi,


On 7/8/2017 11:59 PM, Peter Rosin wrote:
> On 2017-07-08 23:22, Andy Shevchenko wrote:
> > On Sat, Jul 8, 2017 at 9:12 PM,
> > <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> wrote:
> > > From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> > >
> > > Add dummy functions to avoid compile time issues when CONFIG_MULTIPLEXER
> > > is not enabled.
> > I don't think the error return code is okay to all of them. The return
> > value should be choosen carefully (for some functions it's okay IMO to
> > return 0).
> BTW, is ENODEV correct for this situation? I have this nagging feeling
> that ENODEV is over-used?
I used ENODEV to signify that the MUX device is not available/enabled.
> And again, all these stubs should all be inlines, or things will break it
> this file is included more than once.
I will fix the inline problem in next version.
> > > Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
> > > ---
> > >   include/linux/mux/consumer.h | 38 ++++++++++++++++++++++++++++++++++++++
> > >   1 file changed, 38 insertions(+)
> > >
> > > Changes since v1:
> > >   * Changed #ifdef to #if IS_ENABLED.
> > >
> > > diff --git a/include/linux/mux/consumer.h b/include/linux/mux/consumer.h
> > > index 5577e1b..df78988 100644
> > > --- a/include/linux/mux/consumer.h
> > > +++ b/include/linux/mux/consumer.h
> > > @@ -16,6 +16,7 @@
> > >   struct device;
> > >   struct mux_control;
> > >
> > > +#if IS_ENABLED(CONFIG_MULTIPLEXER)
> > >   unsigned int mux_control_states(struct mux_control *mux);
> > >   int __must_check mux_control_select(struct mux_control *mux,
> > >                                      unsigned int state);
> > > @@ -29,4 +30,41 @@ void mux_control_put(struct mux_control *mux);
> > >   struct mux_control *devm_mux_control_get(struct device *dev,
> > >                                           const char *mux_name);
> > >
> > > +#else
> > > +unsigned int mux_control_states(struct mux_control *mux)
> > > +{
> > > +       return -ENODEV;
> > Peter, is here we are obliged to return error code in such case?
> Since it will presumably be difficult to obtain a mux_control
> w/o the mux-core being present, it doesn't matter much what
> most of these stubs return.
>
> For this stub, 0 is perhaps best, since the kernel-doc for
> mux_control_states mentions nothing about any error possibility.
Agreed. Since it returns the total number of MUX states, 0 seems to more
appropriate. I can fix it in next version.
> > > +}
> > > +
> > > +int __must_check mux_control_select(struct mux_control *mux,
> > > +                                   unsigned int state)
> > > +{
> > > +       return -ENODEV;
> > return 0; ?
> Maybe. But it doesn't matter much, but in this case the consumer must
> handle errors. See above.
>
> > > +}
> > > +
> > > +int __must_check mux_control_try_select(struct mux_control *mux,
> > > +                                       unsigned int state)
> > > +{
> > > +       return -ENODEV;
> > > +}
> > return 0; ?
> Maybe. But it doesn't matter much, but in this case the consumer must
> handle errors. See above.
>
> > > +
> > > +int mux_control_deselect(struct mux_control *mux)
> > > +{
> > > +       return -ENODEV;
> > > +}
> > return 0; ?
> Probably. See above.
>
> Cheers,
> peda
>
> > > +
> > > +struct mux_control *mux_control_get(struct device *dev, const char *mux_name)
> > > +{
> > > +       return ERR_PTR(-ENODEV);
> > > +}
> > > +
> > > +void mux_control_put(struct mux_control *mux) {}
> > > +
> > > +struct mux_control *devm_mux_control_get(struct device *dev,
> > > +                                        const char *mux_name)
> > > +{
> > > +       return ERR_PTR(-ENODEV);
> > > +}
> > > +#endif
> > > +
> > >   #endif /* _LINUX_MUX_CONSUMER_H */
> > > --
> > > 2.7.4