Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <20191022085924.92783-1-pumahsu@google.com> <20191023083221.GB8828@kuha.fi.intel.com>
 <644d890b-86e8-f05a-cd4c-32937d971a45@roeck-us.net> <20191023142900.GA15396@kuha.fi.intel.com>
 <20191023150126.GA16612@roeck-us.net> <20191023155757.GB15396@kuha.fi.intel.com>
 <CAGCq0LZGz04JCTEJXrBqs4ENybQih6zKWTacq9T9DKPNOQAfMw@mail.gmail.com> <20191024120346.GC15396@kuha.fi.intel.com>
In-Reply-To: <20191024120346.GC15396@kuha.fi.intel.com>
From:   Puma Hsu <pumahsu@google.com>
Date:   Fri, 25 Oct 2019 14:46:54 +0800
Message-ID: <CAGCq0LZcZUD6jUhcnRTQqtoO2MzCuv8hUndkv5Ekcq=sX7oT4w@mail.gmail.com>
Subject: Re: [PATCH V2] usb: typec: Add sysfs node to show connector orientation
To:     Heikki Krogerus <heikki.krogerus@linux.intel.com>
Cc:     Guenter Roeck <linux@roeck-us.net>,
        Greg KH <gregkh@linuxfoundation.org>,
        Badhri Jagan Sridharan <badhri@google.com>,
        Kyle Tso <kyletso@google.com>,
        Albert Wang <albertccwang@google.com>,
        Chien Kun Niu <rickyniu@google.com>,
        linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hi Heikki,

Sure, I will check about this.
Thanks for advising me.

Thanks in advance.
Puma Hsu


On Thu, Oct 24, 2019 at 8:06 PM Heikki Krogerus
<heikki.krogerus@linux.intel.com> wrote:
>
> Hi,
>
> On Thu, Oct 24, 2019 at 05:02:18PM +0800, Puma Hsu wrote:
> > Yes, generally this might be purely informational or be a dynamically
> > debuggable
> > mechanism for end user as I mentioned in previous discussion
> > thread(https://lkml.org/lkml/2019/10/22/198).
> > Could I know if it is not suitable that we expose a file for
> > informational usage?
> >
> > If everyone agreed above, about the definition of =E2=80=9Cunknown=E2=
=80=9D and the condition
> > =E2=80=9Cdon=E2=80=99t know the orientation=E2=80=9D, what about adding=
 additional return value?
> >   1. For original =E2=80=9Cunknown=E2=80=9D, it is a generic unknown st=
ate which can
> > indicate no
> >       matter connector is disconnected, cannot specify which cc side
> > is configured(such as Ra-Ra),
> >       or even driver can not know the orientation.
> >   2. New additional value =E2=80=9Cunavailable=E2=80=9D, it can be used=
 to
> > specifically explicate that
> >       driver can not know the orientation.
> > Take UCSI as example, it can use generic =E2=80=9Cunknown=E2=80=9D or =
=E2=80=9Cunavailable=E2=80=9D if
> > it wants.
> > But if it exposes =E2=80=9Cunavailable=E2=80=9D, then application in us=
er space can
> > know that this attribute is not useful.
> >
> > I summarize the proposal definition below:
> >  - unknown (generic unknown. driver don=E2=80=99t or can=E2=80=99t know=
 the polarity,
> >                       e.g. disconnected, both cc1 and cc2 are the same,=
 )
> >  - normal (configured in cc1 side)
> >  - reversed (configured in cc2 side)
> >  - unavailable (not support the polarity detection)
>
> Now the attribute would be supplying two types of information:
>
>         1) Does the driver know the orientation
>         2) The current orientation
>
> Let's not do that! If you really need this, then just implement the
> ".is_visible" callback with it. You just need to add a flag to the
> struct typec_capability that tells does the driver know the
> orientation or not. Something like:
>
>         unsigned int orientation_aware:1;
>
> We already "hide" the identity information if the underlying driver
> is unable to supply it. By making this attribute optional as well (by
> hiding it when it's not known), the style of exposing the information
> is kept the same throughout the class.
>
> thanks,
>
> --
> heikki