linux-kernel - Re: [PATCH v2 3/3] usb: typec: tcpm: Get Sink VDO from fwnode

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Date:   Mon, 1 Feb 2021 13:11:30 +0800
From:   Kyle Tso <kyletso@...gle.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Hans de Goede <hdegoede@...hat.com>, robh+dt@...nel.org,
        Badhri Jagan Sridharan <badhri@...gle.com>,
        USB <linux-usb@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 3/3] usb: typec: tcpm: Get Sink VDO from fwnode

On Mon, Feb 1, 2021 at 12:02 AM Guenter Roeck <linux@...ck-us.net> wrote:
>
> On 1/31/21 7:18 AM, Kyle Tso wrote:
> > Commit a079973f462a ("usb: typec: tcpm: Remove tcpc_config
> > configuration mechanism") removed the tcpc_config which includes the
> > Sink VDO and it is not yet added back with fwnode. Add it now.
> >
> > Signed-off-by: Kyle Tso <kyletso@...gle.com>
> > ---
> > Changes since v1:
> > - updated the commit message
> >
> >  drivers/usb/typec/tcpm/tcpm.c | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> >
> > diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> > index 403a483645dd..84c8a52f8af1 100644
> > --- a/drivers/usb/typec/tcpm/tcpm.c
> > +++ b/drivers/usb/typec/tcpm/tcpm.c
> > @@ -5677,6 +5677,18 @@ static int tcpm_fw_get_caps(struct tcpm_port *port,
> >                       port->new_source_frs_current = frs_current;
> >       }
> >
> > +     ret = fwnode_property_read_u32_array(fwnode, "sink-vdos", NULL, 0);
>
> fwnode_property_count_u32(), maybe ?
>
That's the same and looks like fwnode_property_count_u32 is better to read.
I will revise it in the next version.

> > +     if (ret <= 0 && ret != -EINVAL) {
> > +             return -EINVAL;
>
> Why return any error except -EINVAL (including return values of 0) as -EINVAL,
> and -EINVAL as no error ?
>
sink-vdos is not a mandatory property which means -EINVAL is acceptable.

If the return < 0 and the value is not -EINVAL, it means that the
error is other than "not present" in the device tree.
If the return == 0, it means that the sink-vdos is present in the
device tree but no value inside it.
Both of the above situations are not acceptable.

> > +     } else if (ret > 0) {
> > +             port->nr_snk_vdo = min(ret, VDO_MAX_OBJECTS);
> > +             ret = fwnode_property_read_u32_array(fwnode, "sink-vdos",
> > +                                                  port->snk_vdo,
> > +                                                  port->nr_snk_vdo);
> > +             if (ret < 0)
> > +                     return -EINVAL;
>
> static analyzer code used to complain about overriding error codes.
> Not sure if that is still true. Either case, why not return the
> original error ?
>
Returning the original error codes is good. I just followed the return
value of other error handling in this function.
will revise it in the next version.

Thanks,
Kyle



> Thanks,
> Guenter
>
> > +     }
> > +
> >       return 0;
> >  }
> >
> >
>