Re: [PATCH 2/4] usb: typec: hd3ss3220: use typec_get_fw_cap() to fill typec_cap

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

On Thu, Nov 07, 2024 at 03:24:44PM +0000, Facklam, Olivér wrote:
> Hello Heikki,
> 
> > -----Original Message-----
> > From: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> > Sent: Thursday, November 7, 2024 3:21 PM
> > To: Facklam, Olivér <oliver.facklam@zuehlke.com>
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>; linux-
> > usb@vger.kernel.org; linux-kernel@vger.kernel.org; von Heyl, Benedict
> > <benedict.vonheyl@zuehlke.com>; Först, Mathis
> > <mathis.foerst@zuehlke.com>; Glettig, Michael
> > <Michael.Glettig@zuehlke.com>
> > Subject: Re: [PATCH 2/4] usb: typec: hd3ss3220: use typec_get_fw_cap() to fill
> > typec_cap
> > 
> > Hi Oliver,
> > 
> > On Thu, Nov 07, 2024 at 12:43:28PM +0100, Oliver Facklam via B4 Relay
> > wrote:
> > > From: Oliver Facklam <oliver.facklam@zuehlke.com>
> > >
> > > The type, data, and prefer_role properties were previously hard-coded
> > > when creating the struct typec_capability.
> > >
> > > Use typec_get_fw_cap() to populate these fields based on the
> > > respective fwnode properties.
> > >
> > > Signed-off-by: Oliver Facklam <oliver.facklam@zuehlke.com>
> > > ---
> > >  drivers/usb/typec/hd3ss3220.c | 8 ++++----
> > >  1 file changed, 4 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/usb/typec/hd3ss3220.c
> > > b/drivers/usb/typec/hd3ss3220.c index
> > >
> > 56f74bf70895ca701083bde44a5bbe0b691551e1..e6e4b1871b5d805f8c3671
> > 31509f
> > > 4e6ec0d2b5f0 100644
> > > --- a/drivers/usb/typec/hd3ss3220.c
> > > +++ b/drivers/usb/typec/hd3ss3220.c
> > > @@ -259,12 +259,12 @@ static int hd3ss3220_probe(struct i2c_client
> > *client)
> > >  		goto err_put_fwnode;
> > >  	}
> > >
> > > -	typec_cap.prefer_role = TYPEC_NO_PREFERRED_ROLE;
> > > +	ret = typec_get_fw_cap(&typec_cap, connector);
> > > +	if (ret)
> > > +		goto err_put_role;
> > 
> > You are not leaving any fallback here. Are you sure all the existing systems
> > supply those properties?
> > 
> > There is another problem. At least "data-role" property is optional, but that
> > will in practice make it a requirement.
> 
> I missed that typec_get_fw_cap() was not setting a default if the property is absent.
> 
> > 
> > I think it would be safer to use the values from the device properties only if
> > they are available. Otherwise simply use default values.
> 
> I'll add back the previous values as defaults before calling typec_get_fw_cap().
> That will make data-role and try-power-role optional again, as intended.
> 
> However, "power-role" seems to be required by the function. Is this expected?

Yes.

> Or should I write my own fwnode parsing logic?

No, don't do that.

You can check the return value. If it's -EINVAL or -ENXIO, the
properties are not there, and you can safely use the defaults.
Otherwise, consider the failure as critical.

thanks,

-- 
heikki