Re: [PATCH] usb: typec: tcpm: Export partner Source Capabilities

[Guenter Roeck]

On 2/14/19 6:17 AM, Adam Thomson wrote:
> On 12 February 2019 16:20, Guenter Roeck wrote:
>
> > On 2/12/19 2:54 AM, Greg KH wrote:
> > > On Tue, Feb 12, 2019 at 06:29:39PM +0800, Kyle Tso wrote:
> > > > On Thu, Jan 31, 2019 at 3:02 PM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
> > wrote:
> > > > > On Thu, Jan 31, 2019 at 11:54:11AM +0800, Kyle Tso wrote:
> > > > > > Provide a function to get the partner Source Capabilities.
> > > > > >
> > > > > > Signed-off-by: Kyle Tso <kyletso@xxxxxxxxxx>
> > > > > > ---
> > > > > >    drivers/usb/typec/tcpm/tcpm.c | 23 +++++++++++++++++++++++
> > > > > >    include/linux/usb/tcpm.h      |  1 +
> > > > > >    2 files changed, 24 insertions(+)
> > > > > >
> > > > > > diff --git a/drivers/usb/typec/tcpm/tcpm.c
> > > > > b/drivers/usb/typec/tcpm/tcpm.c
> > > > > > index f1d3e54210df..29cd84ba9960 100644
> > > > > > --- a/drivers/usb/typec/tcpm/tcpm.c
> > > > > > +++ b/drivers/usb/typec/tcpm/tcpm.c
> > > > > > @@ -4494,6 +4494,29 @@ int tcpm_update_sink_capabilities(struct
> > > > > tcpm_port *port, const u32 *pdo,
> > > > > >    }
> > > > > >    EXPORT_SYMBOL_GPL(tcpm_update_sink_capabilities);
> > > > > >
> > > > > > +/*
> > > > > > + * Don't call this function in interrupt context. Caller needs to
> > > > > > +free
> > > > > the
> > > > > > + * memory itself.
> > > > > > + */
> > > > > > +int tcpm_get_partner_src_caps(struct tcpm_port *port, u32
> > > > > > +**src_pdo) {
> > > > > > +     unsigned int nr_pdo;
> > > > > > +
> > > > > > +     if (port->nr_source_caps == 0)
> > > > > > +             return -ENODATA;
> > > > > > +
> > > > > > +     *src_pdo = kcalloc(port->nr_source_caps, sizeof(u32), GFP_KERNEL);
> > > > > > +     if (!src_pdo)
> > > > > > +             return -ENOMEM;
> > > > > > +
> > > > > > +     mutex_lock(&port->lock);
> > > > > > +     nr_pdo = tcpm_copy_pdos(*src_pdo, port->source_caps,
> > > > > > +                             port->nr_source_caps);
> > > > > > +     mutex_unlock(&port->lock);
> > > > > > +     return nr_pdo;
> > > > > > +}
> > > > > > +EXPORT_SYMBOL_GPL(tcpm_get_partner_src_caps);
> > > > >
> > > > > We don't add new functions that no one uses :(
> > > > This function is useful if the PD Device Policy Manager is
> > > > implemented outside of TCPM.
> > > > In this situation, Device Policy Manager needs to know the partner
> > > > capabilities to optimize the charging process.
> > >
> > > And where is that code?
> >
> > Agreed - that code should be sent upstream as well to let us see the entire
> > context.
> >
> > > > Take existing functions in TCPM for example:
> > > > Function "tcpm_update_sink_capabilities" and
> > > > "tcpm_update_source_capabilities" are exposed as well. And no one
> > > > uses them now.
> > >
> > > Great, let's go delete them now, we should not have apis that no one
> > > uses.  This isn't a new thing...
> >
> > I sent a patch to do just that. Quite frankly I don't recal why I thought those
> > functions might be needed.
>
> As a mind jog - https://lkml.org/lkml/2017/11/27/1256 :)

Nice find. However, since the code using it was never implemented, I think it
is prudent at this point to remove the code. It can be reintroduced if/when needed,
and at that point be tested properly.

Thanks,
Guenter