linux-kernel - Re: [PATCH v2] usb:typec: Add sysfs support for Type C connector's physical location

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Message-ID: <CAJZ5v0ipcdUqTEFn075NeioyHRDKy2j_pYZOBKgqnx_c1=q5Pw@mail.gmail.com>
Date:   Tue, 1 Mar 2022 20:11:06 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Won Chung <wonchung@...gle.com>
Cc:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Benson Leung <bleung@...omium.org>,
        Prashant Malani <pmalani@...omium.org>,
        "open list:ULTRA-WIDEBAND (UWB) SUBSYSTEM:" 
        <linux-usb@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] usb:typec: Add sysfs support for Type C connector's
 physical location

On Tue, Mar 1, 2022 at 7:57 PM Won Chung <wonchung@...gle.com> wrote:
>
> On Tue, Mar 1, 2022 at 1:33 AM Heikki Krogerus
> <heikki.krogerus@...ux.intel.com> wrote:
> >
> > Hi Won,
> >
> > On Tue, Mar 01, 2022 at 02:26:25AM +0000, Won Chung wrote:
> > > When ACPI table includes _PLD field for a Type C connector, share _PLD
> > > values in its sysfs. _PLD stands for physical location of device.
> > >
> > > Currently without connector's location information, when there are
> > > multiple Type C ports, it is hard to distinguish which connector
> > > corresponds to which physical port at which location. For example, when
> > > there are two Type C connectors, it is hard to find out which connector
> > > corresponds to the Type C port on the left panel versus the Type C port
> > > on the right panel. With location information provided, we can determine
> > > which specific device at which location is doing what.
> > >
> > > _PLD output includes much more fields, but only generic fields are added
> > > and exposed to sysfs, so that non-ACPI devices can also support it in
> > > the future. The minimal generic fields needed for locating a port are
> > > the following.
> > > - panel
> > > - vertical_position
> > > - horizontal_position
> > > - dock
> > > - lid
> > >
> > > Signed-off-by: Won Chung <wonchung@...gle.com>
> > > ---
> > >
> > > Changes in v2:
> > > - Use string for location.
> > > - Clarify get_pld() with naming and return type.
> > >
> > >  Documentation/ABI/testing/sysfs-class-typec |  35 ++++++
> > >  drivers/usb/typec/class.c                   | 113 ++++++++++++++++++++
> > >  drivers/usb/typec/class.h                   |   3 +
> > >  3 files changed, 151 insertions(+)
> > >
> > > diff --git a/Documentation/ABI/testing/sysfs-class-typec b/Documentation/ABI/testing/sysfs-class-typec
> > > index 75088ecad202..4497a5aeb063 100644
> > > --- a/Documentation/ABI/testing/sysfs-class-typec
> > > +++ b/Documentation/ABI/testing/sysfs-class-typec
> > > @@ -141,6 +141,41 @@ Description:
> > >               - "reverse": CC2 orientation
> > >               - "unknown": Orientation cannot be determined.
> > >
> > > +What:                /sys/class/typec/<port>/location/panel
> > > +Date:                March 2022
> > > +Contact:     Won Chung <wonchung@...gle.com>
> > > +Description:
> > > +             Describes which panel surface of the system’s housing the
> > > +             port resides on.
> > > +
> > > +What:                /sys/class/typec/<port>/location/vertical_position
> > > +Date:                March 2022
> > > +Contact:     Won Chung <wonchung@...gle.com>
> > > +Description:
> > > +             Describes vertical position of the port on the panel surface.
> > > +             Valid values: upper, center, lower
> > > +
> > > +What:                /sys/class/typec/<port>/location/horizontal_position
> > > +Date:                March 2022
> > > +Contact:     Won Chung <wonchung@...gle.com>
> > > +Description:
> > > +             Describes horizontal position of the port on the panel surface.
> > > +             Valid values: left, center, right
> > > +
> > > +What:                /sys/class/typec/<port>/location/dock
> > > +Date:                March 2022
> > > +Contact:     Won Chung <wonchung@...gle.com>
> > > +Description:
> > > +             Set as "yes" if the port resides in a docking station or a port
> > > +             replicator, otherwise set as "no".
> > > +
> > > +What:                /sys/class/typec/<port>/location/lid
> > > +Date:                March 2022
> > > +Contact:     Won Chung <wonchung@...gle.com>
> > > +Description:
> > > +             Set as "yes" if the port resides on the lid of laptop system,
> > > +             otherwise set as "no".
> > > +
> >
> > I've probable lost track of the topic during my winter break, I'm
> > sorry about that, but why are you proposing now that this should be
> > made Type-C specific?
> > This information is not Type-C specific, so it definitely does not
> > belong here.
> >
> > Br,
> >
> > --
> > heikki
>
> Hi Heikki,
>
> Thank you for the comment. Sorry that my description was not clear.
> This is follow up from "[PATCH v6] ACPI: device_sysfs: Add sysfs
> support for _PLD" in which Rafael suggested to have generic location
> in Type C connector than adding PLD specifically to ACPI device.

Well, this doesn't have to be /sys/class/typec/<port>/location/ though.

For example, the device location information can be exposed in a more
generic way is /sys/devices/.../location/ for all devices for which it
is available, somewhat in analogy to /sys/devices/.../power/.