linux-kernel - Re: [PATCH v2 05/10] usb: typec: Implement automated mode selection

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Message-ID: <CAMMMRMeYG-bvYSiE7K8AutorvyoiXypHXv_1z62Rvh_JNazd9g@mail.gmail.com>
Date: Thu, 31 Jul 2025 18:09:30 +0200
From: Andrei Kuchynski <akuchynski@...omium.org>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Heikki Krogerus <heikki.krogerus@...ux.intel.com>, 
	Abhishek Pandit-Subedi <abhishekpandit@...omium.org>, Benson Leung <bleung@...omium.org>, 
	Jameson Thies <jthies@...gle.com>, Tzung-Bi Shih <tzungbi@...nel.org>, linux-usb@...r.kernel.org, 
	chrome-platform@...ts.linux.dev, Guenter Roeck <groeck@...omium.org>, 
	Dmitry Baryshkov <lumag@...nel.org>, "Christian A. Ehrhardt" <lk@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 05/10] usb: typec: Implement automated mode selection

On Thu, Jul 24, 2025 at 10:39 AM Andrei Kuchynski
<akuchynski@...omium.org> wrote:
>
> Proposed sysfs entries for V3:
>
> - portN/portN.M/priority, RW.
> This attribute assigns a unique priority to each mode. If a user
> attempts to input a value that is already in use, the existing mode at
> that priority will have its priority incremented by one to accommodate
> the new input. Users cannot disable a mode via this entry; disabling
> is handled by `active` for altmodes and `usb_capability` for USB4 mode
>
> - portN/mode_priorities, RO.
> Provides a prioritized list of all available modes for the port,
> formatted as a space-separated string (e.g., "USB4 TBT DP").
>
> - portN-partner/mode_selection, RW.
> Write: 1/0 to trigger or cancel mode selection.
> Read:  Provides a prioritized list of all available modes for the
> partner. Modes currently in progress are indicated by parentheses
> (e.g., "USB4 (TBT) DP"). Active modes are enclosed in brackets
> (e.g., "USB4 [TBT] DP").
>
> - portN-partner.M/entry_result, RO.
> Represents a mode state for this altmode, e.g. "none", "active",
> "in progress", "cable error", "timeout".
>
> - portN/usb4_priority, RW.
> - portN-partner/usb4_entry_result, RO.
> USB4 mode, not being part of `typec_altmode_group`, introduces
> additional attributes with the same meaning as alternate modes
> attributes.
>
> Please let me know if you have any questions, require further
> clarification on these proposed sysfs entries, or have objections to
> them.

Regarding the sysfs attributes, Heikki, do you have any suggestions or
disagreements? Please let me know your thoughts.

Additionally, for consistency, it would be beneficial to use names
"DisplayPort" and "Thunderbolt3" since they are already recognized
within the kernel. Using these full names rather than "DP" and "TBT"
would be preferable

Thanks,
Andrei