linux-kernel - Re: [PATCH V2] usb: typec: Add sysfs node to show connector orientation

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Message-ID: <CAGCq0LZcZUD6jUhcnRTQqtoO2MzCuv8hUndkv5Ekcq=sX7oT4w@mail.gmail.com>
Date:   Fri, 25 Oct 2019 14:46:54 +0800
From:   Puma Hsu <pumahsu@...gle.com>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Greg KH <gregkh@...uxfoundation.org>,
        Badhri Jagan Sridharan <badhri@...gle.com>,
        Kyle Tso <kyletso@...gle.com>,
        Albert Wang <albertccwang@...gle.com>,
        Chien Kun Niu <rickyniu@...gle.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] usb: typec: Add sysfs node to show connector orientation

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@...ux.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 “unknown” and the condition
> > “don’t know the orientation”, what about adding additional return value?
> >   1. For original “unknown”, it is a generic unknown state 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 “unavailable”, it can be used to
> > specifically explicate that
> >       driver can not know the orientation.
> > Take UCSI as example, it can use generic “unknown” or “unavailable” if
> > it wants.
> > But if it exposes “unavailable”, then application in user space can
> > know that this attribute is not useful.
> >
> > I summarize the proposal definition below:
> >  - unknown (generic unknown. driver don’t or can’t 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