linux-kernel - Re: [PATCH v5 5/7] usb: typec: Introduce mode

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Message-ID: <aW-eY8JCKNpgwa2I@kuha>
Date: Tue, 20 Jan 2026 17:25:23 +0200
From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To: Andrei Kuchynski <akuchynski@...omium.org>
Cc: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>,
	Benson Leung <bleung@...omium.org>,
	Jameson Thies <jthies@...gle.com>, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, chrome-platform@...ts.linux.dev,
	Tzung-Bi Shih <tzungbi@...nel.org>,
	Guenter Roeck <groeck@...omium.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
	Łukasz Bartosik <ukaszb@...omium.org>,
	Pooja Katiyar <pooja.katiyar@...el.com>,
	Johan Hovold <johan@...nel.org>,
	Hsin-Te Yuan <yuanhsinte@...omium.org>, Madhu M <madhu.m@...el.com>,
	Venkat Jayaraman <venkat.jayaraman@...el.com>
Subject: Re: [PATCH v5 5/7] usb: typec: Introduce mode_selection bit

Mon, Jan 19, 2026 at 01:18:22PM +0000, Andrei Kuchynski kirjoitti:
> The port driver sets this bit for an alternate mode description to indicate
> support for the mode selection feature. Once set, individual Alt Mode
> drivers will no longer attempt to activate their respective modes within
> their probe functions. This prevents race conditions and non-prioritized
> activation.
> The bit is not set by default. If left unset, the system retains the
> current behavior where Alt Mode drivers manage their own activation logic.
> 
> Signed-off-by: Andrei Kuchynski <akuchynski@...omium.org>

Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>

> ---
>  drivers/usb/typec/altmodes/displayport.c | 6 ++++--
>  drivers/usb/typec/altmodes/thunderbolt.c | 2 +-
>  drivers/usb/typec/class.c                | 1 +
>  include/linux/usb/typec.h                | 1 +
>  include/linux/usb/typec_altmode.h        | 1 +
>  5 files changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
> index d96ab106a980b..d185688a16b13 100644
> --- a/drivers/usb/typec/altmodes/displayport.c
> +++ b/drivers/usb/typec/altmodes/displayport.c
> @@ -804,8 +804,10 @@ int dp_altmode_probe(struct typec_altmode *alt)
>  	if (plug)
>  		typec_altmode_set_drvdata(plug, dp);
>  
> -	dp->state = plug ? DP_STATE_ENTER_PRIME : DP_STATE_ENTER;
> -	schedule_work(&dp->work);
> +	if (!alt->mode_selection) {
> +		dp->state = plug ? DP_STATE_ENTER_PRIME : DP_STATE_ENTER;
> +		schedule_work(&dp->work);
> +	}
>  
>  	return 0;
>  }
> diff --git a/drivers/usb/typec/altmodes/thunderbolt.c b/drivers/usb/typec/altmodes/thunderbolt.c
> index 6eadf7835f8f6..c4c5da6154da9 100644
> --- a/drivers/usb/typec/altmodes/thunderbolt.c
> +++ b/drivers/usb/typec/altmodes/thunderbolt.c
> @@ -307,7 +307,7 @@ static int tbt_altmode_probe(struct typec_altmode *alt)
>  	typec_altmode_set_drvdata(alt, tbt);
>  	typec_altmode_set_ops(alt, &tbt_altmode_ops);
>  
> -	if (tbt_ready(alt)) {
> +	if (!alt->mode_selection && tbt_ready(alt)) {
>  		if (tbt->plug[TYPEC_PLUG_SOP_P])
>  			tbt->state = TBT_STATE_SOP_P_ENTER;
>  		else if (tbt->plug[TYPEC_PLUG_SOP_PP])
> diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
> index a48c447125184..dbba53f024977 100644
> --- a/drivers/usb/typec/class.c
> +++ b/drivers/usb/typec/class.c
> @@ -655,6 +655,7 @@ typec_register_altmode(struct device *parent,
>  	alt->adev.svid = desc->svid;
>  	alt->adev.mode = desc->mode;
>  	alt->adev.vdo = desc->vdo;
> +	alt->adev.mode_selection = desc->mode_selection;
>  	alt->roles = desc->roles;
>  	alt->id = id;
>  
> diff --git a/include/linux/usb/typec.h b/include/linux/usb/typec.h
> index dbb259d885266..d61ec38216fa9 100644
> --- a/include/linux/usb/typec.h
> +++ b/include/linux/usb/typec.h
> @@ -155,6 +155,7 @@ struct typec_altmode_desc {
>  	/* Only used with ports */
>  	enum typec_port_data	roles;
>  	bool			inactive;
> +	bool			mode_selection;
>  };
>  
>  void typec_partner_set_pd_revision(struct typec_partner *partner, u16 pd_revision);
> diff --git a/include/linux/usb/typec_altmode.h b/include/linux/usb/typec_altmode.h
> index 70026f5f8f997..0513d333b7977 100644
> --- a/include/linux/usb/typec_altmode.h
> +++ b/include/linux/usb/typec_altmode.h
> @@ -37,6 +37,7 @@ struct typec_altmode {
>  	u32				vdo;
>  	unsigned int			active:1;
>  	u8				priority;
> +	bool			mode_selection;
>  
>  	char				*desc;
>  	const struct typec_altmode_ops	*ops;
> -- 
> 2.52.0.457.g6b5491de43-goog

-- 
heikki