[PATCH v5 0/4] USB Type-C alternate mode priorities

[PATCH v5 0/4] USB Type-C alternate mode priorities

[Andrei Kuchynski]

This patch series introduces a mechanism for setting USB Type-C alternate
mode priorities. It allows the user to specify their preferred order for
mode selection, such as USB4, Thunderbolt, or DisplayPort.

A new sysfs attribute named 'priority' is exposed to provide user-space
control over the mode selection process.

This series was tested on a Android OS device running kernel 6.18.0-rc6.

Changes in v5:
- Patches 3 and 4 (v4) have been consolidated into a singular patch,
keeping the mode priority implementation within drivers/usb/typec/class.c.

Andrei Kuchynski (4):
  usb: typec: Add mode_control field to port property
  platform/chrome: cros_ec_typec: Set no_mode_control flag
  usb: typec: ucsi: Set no_mode_control flag
  usb: typec: Expose alternate mode priority via sysfs

 Documentation/ABI/testing/sysfs-class-typec | 11 +++
 drivers/platform/chrome/cros_ec_typec.c     |  1 +
 drivers/usb/typec/class.c                   | 99 ++++++++++++++++++++-
 drivers/usb/typec/class.h                   |  1 +
 drivers/usb/typec/ucsi/ucsi.c               |  1 +
 include/linux/usb/typec.h                   |  2 +
 include/linux/usb/typec_altmode.h           |  1 +
 7 files changed, 112 insertions(+), 4 deletions(-)

-- 
2.52.0.rc2.455.g230fcf2819-goog

[PATCH v5 1/4] usb: typec: Add mode_control field to port property

[Andrei Kuchynski]

This new field in the port properties dictates whether the Platform Policy
Manager (PPM) allows the OS Policy Manager (OPM) to change the currently
active, negotiated alternate mode.

Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
---
 drivers/usb/typec/class.c | 9 ++++++---
 drivers/usb/typec/class.h | 1 +
 include/linux/usb/typec.h | 2 ++
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
index 9b2647cb199b..a5327e444265 100644
--- a/drivers/usb/typec/class.c
+++ b/drivers/usb/typec/class.c
@@ -457,11 +457,13 @@ static umode_t typec_altmode_attr_is_visible(struct kobject *kobj,
 					     struct attribute *attr, int n)
 {
 	struct typec_altmode *adev = to_typec_altmode(kobj_to_dev(kobj));
+	struct typec_port *port = typec_altmode2port(adev);
 
 	if (attr == &dev_attr_active.attr)
-		if (!is_typec_port(adev->dev.parent) &&
-		    (!adev->ops || !adev->ops->activate))
-			return 0444;
+		if (!is_typec_port(adev->dev.parent)) {
+			if (!port->mode_control || !adev->ops || !adev->ops->activate)
+				return 0444;
+		}
 
 	return attr->mode;
 }
@@ -2694,6 +2696,7 @@ struct typec_port *typec_register_port(struct device *parent,
 	}
 
 	port->pd = cap->pd;
+	port->mode_control = !cap->no_mode_control;
 
 	ret = device_add(&port->dev);
 	if (ret) {
diff --git a/drivers/usb/typec/class.h b/drivers/usb/typec/class.h
index db2fe96c48ff..2e89a83c2eb7 100644
--- a/drivers/usb/typec/class.h
+++ b/drivers/usb/typec/class.h
@@ -62,6 +62,7 @@ struct typec_port {
 	struct mutex			partner_link_lock;
 
 	enum typec_orientation		orientation;
+	bool				mode_control;
 	struct typec_switch		*sw;
 	struct typec_mux		*mux;
 	struct typec_retimer		*retimer;
diff --git a/include/linux/usb/typec.h b/include/linux/usb/typec.h
index 309251572e2e..59d5fd7e4ff4 100644
--- a/include/linux/usb/typec.h
+++ b/include/linux/usb/typec.h
@@ -287,6 +287,7 @@ enum usb_pd_svdm_ver {
  * @prefer_role: Initial role preference (DRP ports).
  * @accessory: Supported Accessory Modes
  * @usb_capability: Supported USB Modes
+ * @no_mode_control: Ability to manage Alternate Modes
  * @fwnode: Optional fwnode of the port
  * @driver_data: Private pointer for driver specific info
  * @pd: Optional USB Power Delivery Support
@@ -304,6 +305,7 @@ struct typec_capability {
 	enum typec_accessory	accessory[TYPEC_MAX_ACCESSORY];
 	unsigned int		orientation_aware:1;
 	u8			usb_capability;
+	bool			no_mode_control;
 
 	struct fwnode_handle	*fwnode;
 	void			*driver_data;
-- 
2.52.0.rc2.455.g230fcf2819-goog

Re: [PATCH v5 1/4] usb: typec: Add mode_control field to port property

[Benson Leung]

[-- Attachment #1: Type: text/plain, Size: 2997 bytes --]

Hi Andrei,

On Mon, Nov 24, 2025 at 12:46:36PM +0000, Andrei Kuchynski wrote:
> This new field in the port properties dictates whether the Platform Policy
> Manager (PPM) allows the OS Policy Manager (OPM) to change the currently
> active, negotiated alternate mode.
> 
> Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

Reviewed-by: Benson Leung <bleung@chromium.org>

> ---
>  drivers/usb/typec/class.c | 9 ++++++---
>  drivers/usb/typec/class.h | 1 +
>  include/linux/usb/typec.h | 2 ++
>  3 files changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
> index 9b2647cb199b..a5327e444265 100644
> --- a/drivers/usb/typec/class.c
> +++ b/drivers/usb/typec/class.c
> @@ -457,11 +457,13 @@ static umode_t typec_altmode_attr_is_visible(struct kobject *kobj,
>  					     struct attribute *attr, int n)
>  {
>  	struct typec_altmode *adev = to_typec_altmode(kobj_to_dev(kobj));
> +	struct typec_port *port = typec_altmode2port(adev);
>  
>  	if (attr == &dev_attr_active.attr)
> -		if (!is_typec_port(adev->dev.parent) &&
> -		    (!adev->ops || !adev->ops->activate))
> -			return 0444;
> +		if (!is_typec_port(adev->dev.parent)) {
> +			if (!port->mode_control || !adev->ops || !adev->ops->activate)
> +				return 0444;
> +		}
>  
>  	return attr->mode;
>  }
> @@ -2694,6 +2696,7 @@ struct typec_port *typec_register_port(struct device *parent,
>  	}
>  
>  	port->pd = cap->pd;
> +	port->mode_control = !cap->no_mode_control;
>  
>  	ret = device_add(&port->dev);
>  	if (ret) {
> diff --git a/drivers/usb/typec/class.h b/drivers/usb/typec/class.h
> index db2fe96c48ff..2e89a83c2eb7 100644
> --- a/drivers/usb/typec/class.h
> +++ b/drivers/usb/typec/class.h
> @@ -62,6 +62,7 @@ struct typec_port {
>  	struct mutex			partner_link_lock;
>  
>  	enum typec_orientation		orientation;
> +	bool				mode_control;
>  	struct typec_switch		*sw;
>  	struct typec_mux		*mux;
>  	struct typec_retimer		*retimer;
> diff --git a/include/linux/usb/typec.h b/include/linux/usb/typec.h
> index 309251572e2e..59d5fd7e4ff4 100644
> --- a/include/linux/usb/typec.h
> +++ b/include/linux/usb/typec.h
> @@ -287,6 +287,7 @@ enum usb_pd_svdm_ver {
>   * @prefer_role: Initial role preference (DRP ports).
>   * @accessory: Supported Accessory Modes
>   * @usb_capability: Supported USB Modes
> + * @no_mode_control: Ability to manage Alternate Modes
>   * @fwnode: Optional fwnode of the port
>   * @driver_data: Private pointer for driver specific info
>   * @pd: Optional USB Power Delivery Support
> @@ -304,6 +305,7 @@ struct typec_capability {
>  	enum typec_accessory	accessory[TYPEC_MAX_ACCESSORY];
>  	unsigned int		orientation_aware:1;
>  	u8			usb_capability;
> +	bool			no_mode_control;
>  
>  	struct fwnode_handle	*fwnode;
>  	void			*driver_data;
> -- 
> 2.52.0.rc2.455.g230fcf2819-goog
> 

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[PATCH v5 2/4] platform/chrome: cros_ec_typec: Set no_mode_control flag

[Andrei Kuchynski]

This flag specifies that the Embedded Controller (EC) must receive explicit
approval from the Application Processor (AP) before initiating Type-C
alternate modes or USB4 mode.

Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Acked-by: Tzung-Bi Shih <tzungbi@kernel.org>
---
 drivers/platform/chrome/cros_ec_typec.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
index b712bcff6fb2..c0806c562bb9 100644
--- a/drivers/platform/chrome/cros_ec_typec.c
+++ b/drivers/platform/chrome/cros_ec_typec.c
@@ -491,6 +491,7 @@ static int cros_typec_init_ports(struct cros_typec_data *typec)
 
 		cap->driver_data = cros_port;
 		cap->ops = &cros_typec_usb_mode_ops;
+		cap->no_mode_control = !typec->ap_driven_altmode;
 
 		cros_port->port = typec_register_port(dev, cap);
 		if (IS_ERR(cros_port->port)) {
-- 
2.52.0.rc2.455.g230fcf2819-goog

Re: [PATCH v5 2/4] platform/chrome: cros_ec_typec: Set no_mode_control flag

[Benson Leung]

[-- Attachment #1: Type: text/plain, Size: 1203 bytes --]

Hi Andrei,

On Mon, Nov 24, 2025 at 12:46:37PM +0000, Andrei Kuchynski wrote:
> This flag specifies that the Embedded Controller (EC) must receive explicit
> approval from the Application Processor (AP) before initiating Type-C
> alternate modes or USB4 mode.
> 
> Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> Acked-by: Tzung-Bi Shih <tzungbi@kernel.org>

Reviewed-by: Benson Leung <bleung@chromium.org>

> ---
>  drivers/platform/chrome/cros_ec_typec.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
> index b712bcff6fb2..c0806c562bb9 100644
> --- a/drivers/platform/chrome/cros_ec_typec.c
> +++ b/drivers/platform/chrome/cros_ec_typec.c
> @@ -491,6 +491,7 @@ static int cros_typec_init_ports(struct cros_typec_data *typec)
>  
>  		cap->driver_data = cros_port;
>  		cap->ops = &cros_typec_usb_mode_ops;
> +		cap->no_mode_control = !typec->ap_driven_altmode;
>  
>  		cros_port->port = typec_register_port(dev, cap);
>  		if (IS_ERR(cros_port->port)) {
> -- 
> 2.52.0.rc2.455.g230fcf2819-goog
> 

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[PATCH v5 3/4] usb: typec: ucsi: Set no_mode_control flag

[Andrei Kuchynski]

This flag indicates that the PPM allows the OPM to change the currently
negotiated alternate mode using the SET_NEW_CAM command.

Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
---
 drivers/usb/typec/ucsi/ucsi.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
index 9b3df776137a..82c3efd72639 100644
--- a/drivers/usb/typec/ucsi/ucsi.c
+++ b/drivers/usb/typec/ucsi/ucsi.c
@@ -1700,6 +1700,7 @@ static int ucsi_register_port(struct ucsi *ucsi, struct ucsi_connector *con)
 
 	cap->driver_data = con;
 	cap->ops = &ucsi_ops;
+	cap->no_mode_control = !(con->ucsi->cap.features & UCSI_CAP_ALT_MODE_OVERRIDE);
 
 	if (ucsi->version >= UCSI_VERSION_2_0)
 		con->typec_cap.orientation_aware = true;
-- 
2.52.0.rc2.455.g230fcf2819-goog

Re: [PATCH v5 3/4] usb: typec: ucsi: Set no_mode_control flag

[Benson Leung]

[-- Attachment #1: Type: text/plain, Size: 995 bytes --]

On Mon, Nov 24, 2025 at 12:46:38PM +0000, Andrei Kuchynski wrote:
> This flag indicates that the PPM allows the OPM to change the currently
> negotiated alternate mode using the SET_NEW_CAM command.
> 
> Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>

Reviewed-by: Benson Leung <bleung@chromium.org>

> ---
>  drivers/usb/typec/ucsi/ucsi.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
> index 9b3df776137a..82c3efd72639 100644
> --- a/drivers/usb/typec/ucsi/ucsi.c
> +++ b/drivers/usb/typec/ucsi/ucsi.c
> @@ -1700,6 +1700,7 @@ static int ucsi_register_port(struct ucsi *ucsi, struct ucsi_connector *con)
>  
>  	cap->driver_data = con;
>  	cap->ops = &ucsi_ops;
> +	cap->no_mode_control = !(con->ucsi->cap.features & UCSI_CAP_ALT_MODE_OVERRIDE);
>  
>  	if (ucsi->version >= UCSI_VERSION_2_0)
>  		con->typec_cap.orientation_aware = true;
> -- 
> 2.52.0.rc2.455.g230fcf2819-goog
> 

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[PATCH v5 4/4] usb: typec: Expose alternate mode priority via sysfs

[Andrei Kuchynski]

This patch introduces a priority sysfs attribute to the USB Type-C
alternate mode port interface. This new attribute allows user-space to
configure the numeric priority of alternate modes managing their preferred
order of operation. If a new priority value conflicts with an existing
mode's priority, the priorities of the conflicting mode and all subsequent
modes are automatically incremented to ensure uniqueness.

Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
---
 Documentation/ABI/testing/sysfs-class-typec | 11 +++
 drivers/usb/typec/class.c                   | 90 ++++++++++++++++++++-
 include/linux/usb/typec_altmode.h           |  1 +
 3 files changed, 101 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-class-typec b/Documentation/ABI/testing/sysfs-class-typec
index 38e101c17a00..737b76828b50 100644
--- a/Documentation/ABI/testing/sysfs-class-typec
+++ b/Documentation/ABI/testing/sysfs-class-typec
@@ -162,6 +162,17 @@ Description:	Lists the supported USB Modes. The default USB mode that is used
 		- usb3 (USB 3.2)
 		- usb4 (USB4)
 
+What:		/sys/class/typec/<port>/<alt-mode>/priority
+Date:		July 2025
+Contact:	Andrei Kuchynski <akuchynski@chromium.org>
+Description:
+		Displays and allows setting the priority for a specific alternate mode.
+		The priority is an integer in the range 0-255. A lower numerical value
+		indicates a higher priority (0 is the highest).
+		If the new value is already in use by another mode, the priority of the
+		conflicting mode and any subsequent modes will be incremented until they
+		are all unique.
+
 USB Type-C partner devices (eg. /sys/class/typec/port0-partner/)
 
 What:		/sys/class/typec/<port>-partner/accessory_mode
diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
index a5327e444265..049d1829be98 100644
--- a/drivers/usb/typec/class.c
+++ b/drivers/usb/typec/class.c
@@ -445,11 +445,88 @@ svid_show(struct device *dev, struct device_attribute *attr, char *buf)
 }
 static DEVICE_ATTR_RO(svid);
 
+static int increment_duplicated_priority(struct device *dev, void *data)
+{
+	if (is_typec_altmode(dev)) {
+		struct typec_altmode **alt_target = (struct typec_altmode **)data;
+		struct typec_altmode *alt = to_typec_altmode(dev);
+
+		if (alt != *alt_target && alt->priority == (*alt_target)->priority) {
+			alt->priority++;
+			*alt_target = alt;
+			return 1;
+		}
+	}
+	return 0;
+}
+
+static int find_duplicated_priority(struct device *dev, void *data)
+{
+	if (is_typec_altmode(dev)) {
+		struct typec_altmode **alt_target = (struct typec_altmode **)data;
+		struct typec_altmode *alt = to_typec_altmode(dev);
+
+		if (alt != *alt_target && alt->priority == (*alt_target)->priority)
+			return 1;
+	}
+	return 0;
+}
+
+static int typec_mode_set_priority(struct typec_altmode *alt, const u8 priority)
+{
+	struct typec_port *port = to_typec_port(alt->dev.parent);
+	const u8 old_priority = alt->priority;
+	int res = 1;
+
+	alt->priority = priority;
+	while (res) {
+		res = device_for_each_child(&port->dev, &alt, find_duplicated_priority);
+		if (res) {
+			alt->priority++;
+			if (alt->priority == 0) {
+				alt->priority = old_priority;
+				return -EOVERFLOW;
+			}
+		}
+	}
+
+	res = 1;
+	alt->priority = priority;
+	while (res)
+		res = device_for_each_child(&port->dev, &alt,
+				increment_duplicated_priority);
+
+	return 0;
+}
+
+static ssize_t priority_store(struct device *dev,
+			       struct device_attribute *attr,
+			       const char *buf, size_t size)
+{
+	u8 val;
+	int err = kstrtou8(buf, 10, &val);
+
+	if (!err)
+		err = typec_mode_set_priority(to_typec_altmode(dev), val);
+
+	if (!err)
+		return size;
+	return err;
+}
+
+static ssize_t priority_show(struct device *dev,
+			      struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%u\n", to_typec_altmode(dev)->priority);
+}
+static DEVICE_ATTR_RW(priority);
+
 static struct attribute *typec_altmode_attrs[] = {
 	&dev_attr_active.attr,
 	&dev_attr_mode.attr,
 	&dev_attr_svid.attr,
 	&dev_attr_vdo.attr,
+	&dev_attr_priority.attr,
 	NULL
 };
 
@@ -459,11 +536,15 @@ static umode_t typec_altmode_attr_is_visible(struct kobject *kobj,
 	struct typec_altmode *adev = to_typec_altmode(kobj_to_dev(kobj));
 	struct typec_port *port = typec_altmode2port(adev);
 
-	if (attr == &dev_attr_active.attr)
+	if (attr == &dev_attr_active.attr) {
 		if (!is_typec_port(adev->dev.parent)) {
 			if (!port->mode_control || !adev->ops || !adev->ops->activate)
 				return 0444;
 		}
+	} else if (attr == &dev_attr_priority.attr) {
+		if (!is_typec_port(adev->dev.parent) || !port->mode_control)
+			return 0;
+	}
 
 	return attr->mode;
 }
@@ -2484,6 +2565,7 @@ typec_port_register_altmode(struct typec_port *port,
 	struct typec_altmode *adev;
 	struct typec_mux *mux;
 	struct typec_retimer *retimer;
+	int ret;
 
 	mux = typec_mux_get(&port->dev);
 	if (IS_ERR(mux))
@@ -2502,6 +2584,12 @@ typec_port_register_altmode(struct typec_port *port,
 	} else {
 		to_altmode(adev)->mux = mux;
 		to_altmode(adev)->retimer = retimer;
+
+		ret = typec_mode_set_priority(adev, 0);
+		if (ret) {
+			typec_unregister_altmode(adev);
+			return ERR_PTR(ret);
+		}
 	}
 
 	return adev;
diff --git a/include/linux/usb/typec_altmode.h b/include/linux/usb/typec_altmode.h
index f7db3bd4c90e..2c3b6bec2eca 100644
--- a/include/linux/usb/typec_altmode.h
+++ b/include/linux/usb/typec_altmode.h
@@ -28,6 +28,7 @@ struct typec_altmode {
 	int				mode;
 	u32				vdo;
 	unsigned int			active:1;
+	u8				priority;
 
 	char				*desc;
 	const struct typec_altmode_ops	*ops;
-- 
2.52.0.rc2.455.g230fcf2819-goog

Re: [PATCH v5 4/4] usb: typec: Expose alternate mode priority via sysfs

[Abel Vesa]

On 25-11-24 12:46:39, Andrei Kuchynski wrote:
> This patch introduces a priority sysfs attribute to the USB Type-C

Please read submitting patches doc. No "This patch ..." stuff.

The rest of the patch looks OK.

> alternate mode port interface. This new attribute allows user-space to
> configure the numeric priority of alternate modes managing their preferred
> order of operation. If a new priority value conflicts with an existing
> mode's priority, the priorities of the conflicting mode and all subsequent
> modes are automatically incremented to ensure uniqueness.
> 
> Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>

Re: [PATCH v5 4/4] usb: typec: Expose alternate mode priority via sysfs

[Benson Leung]

[-- Attachment #1: Type: text/plain, Size: 6268 bytes --]

On Mon, Nov 24, 2025 at 12:46:39PM +0000, Andrei Kuchynski wrote:
> This patch introduces a priority sysfs attribute to the USB Type-C
> alternate mode port interface. This new attribute allows user-space to
> configure the numeric priority of alternate modes managing their preferred
> order of operation. If a new priority value conflicts with an existing
> mode's priority, the priorities of the conflicting mode and all subsequent
> modes are automatically incremented to ensure uniqueness.
> 
> Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>

Reviewed-by: Benson Leung <bleung@chromium.org>

> ---
>  Documentation/ABI/testing/sysfs-class-typec | 11 +++
>  drivers/usb/typec/class.c                   | 90 ++++++++++++++++++++-
>  include/linux/usb/typec_altmode.h           |  1 +
>  3 files changed, 101 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-typec b/Documentation/ABI/testing/sysfs-class-typec
> index 38e101c17a00..737b76828b50 100644
> --- a/Documentation/ABI/testing/sysfs-class-typec
> +++ b/Documentation/ABI/testing/sysfs-class-typec
> @@ -162,6 +162,17 @@ Description:	Lists the supported USB Modes. The default USB mode that is used
>  		- usb3 (USB 3.2)
>  		- usb4 (USB4)
>  
> +What:		/sys/class/typec/<port>/<alt-mode>/priority
> +Date:		July 2025
> +Contact:	Andrei Kuchynski <akuchynski@chromium.org>
> +Description:
> +		Displays and allows setting the priority for a specific alternate mode.
> +		The priority is an integer in the range 0-255. A lower numerical value
> +		indicates a higher priority (0 is the highest).
> +		If the new value is already in use by another mode, the priority of the
> +		conflicting mode and any subsequent modes will be incremented until they
> +		are all unique.
> +
>  USB Type-C partner devices (eg. /sys/class/typec/port0-partner/)
>  
>  What:		/sys/class/typec/<port>-partner/accessory_mode
> diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
> index a5327e444265..049d1829be98 100644
> --- a/drivers/usb/typec/class.c
> +++ b/drivers/usb/typec/class.c
> @@ -445,11 +445,88 @@ svid_show(struct device *dev, struct device_attribute *attr, char *buf)
>  }
>  static DEVICE_ATTR_RO(svid);
>  
> +static int increment_duplicated_priority(struct device *dev, void *data)
> +{
> +	if (is_typec_altmode(dev)) {
> +		struct typec_altmode **alt_target = (struct typec_altmode **)data;
> +		struct typec_altmode *alt = to_typec_altmode(dev);
> +
> +		if (alt != *alt_target && alt->priority == (*alt_target)->priority) {
> +			alt->priority++;
> +			*alt_target = alt;
> +			return 1;
> +		}
> +	}
> +	return 0;
> +}
> +
> +static int find_duplicated_priority(struct device *dev, void *data)
> +{
> +	if (is_typec_altmode(dev)) {
> +		struct typec_altmode **alt_target = (struct typec_altmode **)data;
> +		struct typec_altmode *alt = to_typec_altmode(dev);
> +
> +		if (alt != *alt_target && alt->priority == (*alt_target)->priority)
> +			return 1;
> +	}
> +	return 0;
> +}
> +
> +static int typec_mode_set_priority(struct typec_altmode *alt, const u8 priority)
> +{
> +	struct typec_port *port = to_typec_port(alt->dev.parent);
> +	const u8 old_priority = alt->priority;
> +	int res = 1;
> +
> +	alt->priority = priority;
> +	while (res) {
> +		res = device_for_each_child(&port->dev, &alt, find_duplicated_priority);
> +		if (res) {
> +			alt->priority++;
> +			if (alt->priority == 0) {
> +				alt->priority = old_priority;
> +				return -EOVERFLOW;
> +			}
> +		}
> +	}
> +
> +	res = 1;
> +	alt->priority = priority;
> +	while (res)
> +		res = device_for_each_child(&port->dev, &alt,
> +				increment_duplicated_priority);
> +
> +	return 0;
> +}
> +
> +static ssize_t priority_store(struct device *dev,
> +			       struct device_attribute *attr,
> +			       const char *buf, size_t size)
> +{
> +	u8 val;
> +	int err = kstrtou8(buf, 10, &val);
> +
> +	if (!err)
> +		err = typec_mode_set_priority(to_typec_altmode(dev), val);
> +
> +	if (!err)
> +		return size;
> +	return err;
> +}
> +
> +static ssize_t priority_show(struct device *dev,
> +			      struct device_attribute *attr, char *buf)
> +{
> +	return sysfs_emit(buf, "%u\n", to_typec_altmode(dev)->priority);
> +}
> +static DEVICE_ATTR_RW(priority);
> +
>  static struct attribute *typec_altmode_attrs[] = {
>  	&dev_attr_active.attr,
>  	&dev_attr_mode.attr,
>  	&dev_attr_svid.attr,
>  	&dev_attr_vdo.attr,
> +	&dev_attr_priority.attr,
>  	NULL
>  };
>  
> @@ -459,11 +536,15 @@ static umode_t typec_altmode_attr_is_visible(struct kobject *kobj,
>  	struct typec_altmode *adev = to_typec_altmode(kobj_to_dev(kobj));
>  	struct typec_port *port = typec_altmode2port(adev);
>  
> -	if (attr == &dev_attr_active.attr)
> +	if (attr == &dev_attr_active.attr) {
>  		if (!is_typec_port(adev->dev.parent)) {
>  			if (!port->mode_control || !adev->ops || !adev->ops->activate)
>  				return 0444;
>  		}
> +	} else if (attr == &dev_attr_priority.attr) {
> +		if (!is_typec_port(adev->dev.parent) || !port->mode_control)
> +			return 0;
> +	}
>  
>  	return attr->mode;
>  }
> @@ -2484,6 +2565,7 @@ typec_port_register_altmode(struct typec_port *port,
>  	struct typec_altmode *adev;
>  	struct typec_mux *mux;
>  	struct typec_retimer *retimer;
> +	int ret;
>  
>  	mux = typec_mux_get(&port->dev);
>  	if (IS_ERR(mux))
> @@ -2502,6 +2584,12 @@ typec_port_register_altmode(struct typec_port *port,
>  	} else {
>  		to_altmode(adev)->mux = mux;
>  		to_altmode(adev)->retimer = retimer;
> +
> +		ret = typec_mode_set_priority(adev, 0);
> +		if (ret) {
> +			typec_unregister_altmode(adev);
> +			return ERR_PTR(ret);
> +		}
>  	}
>  
>  	return adev;
> diff --git a/include/linux/usb/typec_altmode.h b/include/linux/usb/typec_altmode.h
> index f7db3bd4c90e..2c3b6bec2eca 100644
> --- a/include/linux/usb/typec_altmode.h
> +++ b/include/linux/usb/typec_altmode.h
> @@ -28,6 +28,7 @@ struct typec_altmode {
>  	int				mode;
>  	u32				vdo;
>  	unsigned int			active:1;
> +	u8				priority;
>  
>  	char				*desc;
>  	const struct typec_altmode_ops	*ops;
> -- 
> 2.52.0.rc2.455.g230fcf2819-goog
> 

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Re: [PATCH v5 0/4] USB Type-C alternate mode priorities

[Heikki Krogerus]

Hi Andrei, guys,

Mon, Nov 24, 2025 at 12:46:35PM +0000, Andrei Kuchynski kirjoitti:
> This patch series introduces a mechanism for setting USB Type-C alternate
> mode priorities. It allows the user to specify their preferred order for
> mode selection, such as USB4, Thunderbolt, or DisplayPort.
> 
> A new sysfs attribute named 'priority' is exposed to provide user-space
> control over the mode selection process.
> 
> This series was tested on a Android OS device running kernel 6.18.0-rc6.
> 
> Changes in v5:
> - Patches 3 and 4 (v4) have been consolidated into a singular patch,
> keeping the mode priority implementation within drivers/usb/typec/class.c.
> 
> Andrei Kuchynski (4):
>   usb: typec: Add mode_control field to port property
>   platform/chrome: cros_ec_typec: Set no_mode_control flag
>   usb: typec: ucsi: Set no_mode_control flag
>   usb: typec: Expose alternate mode priority via sysfs
> 
>  Documentation/ABI/testing/sysfs-class-typec | 11 +++
>  drivers/platform/chrome/cros_ec_typec.c     |  1 +
>  drivers/usb/typec/class.c                   | 99 ++++++++++++++++++++-
>  drivers/usb/typec/class.h                   |  1 +
>  drivers/usb/typec/ucsi/ucsi.c               |  1 +
>  include/linux/usb/typec.h                   |  2 +
>  include/linux/usb/typec_altmode.h           |  1 +
>  7 files changed, 112 insertions(+), 4 deletions(-)

These are okay by me. I think we can move to the next step. But I'm
not sure we apply these before that, because the file has no effect
at the moment.

Br,

-- 
heikki

Re: [PATCH v5 0/4] USB Type-C alternate mode priorities

[Andrei Kuchynski]

On Wed, Nov 26, 2025 at 10:23 AM Heikki Krogerus
<heikki.krogerus@linux.intel.com> wrote:
>
> Hi Andrei, guys,
>
> Mon, Nov 24, 2025 at 12:46:35PM +0000, Andrei Kuchynski kirjoitti:
> > This patch series introduces a mechanism for setting USB Type-C alternate
> > mode priorities. It allows the user to specify their preferred order for
> > mode selection, such as USB4, Thunderbolt, or DisplayPort.
> >
> > A new sysfs attribute named 'priority' is exposed to provide user-space
> > control over the mode selection process.
> >
> > This series was tested on a Android OS device running kernel 6.18.0-rc6.
> >
> > Changes in v5:
> > - Patches 3 and 4 (v4) have been consolidated into a singular patch,
> > keeping the mode priority implementation within drivers/usb/typec/class.c.
> >
> > Andrei Kuchynski (4):
> >   usb: typec: Add mode_control field to port property
> >   platform/chrome: cros_ec_typec: Set no_mode_control flag
> >   usb: typec: ucsi: Set no_mode_control flag
> >   usb: typec: Expose alternate mode priority via sysfs
> >
> >  Documentation/ABI/testing/sysfs-class-typec | 11 +++
> >  drivers/platform/chrome/cros_ec_typec.c     |  1 +
> >  drivers/usb/typec/class.c                   | 99 ++++++++++++++++++++-
> >  drivers/usb/typec/class.h                   |  1 +
> >  drivers/usb/typec/ucsi/ucsi.c               |  1 +
> >  include/linux/usb/typec.h                   |  2 +
> >  include/linux/usb/typec_altmode.h           |  1 +
> >  7 files changed, 112 insertions(+), 4 deletions(-)
>
> These are okay by me. I think we can move to the next step. But I'm
> not sure we apply these before that, because the file has no effect
> at the moment.
>
> Br,
>
> --
> heikki

Hi Heikki, Abel, Benson,

Thank you for your review of the series.
I will send the subsequent series detailing how we are going to use
priorities in cros_ec_typec and cros_ec_ucsi drivers.

Thanks,
Andrei