[PATCH v2 0/5] USB Type-C alternate mode priorities

[PATCH v2 0/5] 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 6.16.

Changes in v2:
- The priority variable is now a member of the typec_altmode struct
- typec_altmode2port is used to obtain the typec_port struct pointer
- Default priorities are now set based on the order of registration
- The mode_control capability is enabled by default
- The mode_selection_state struct will be introduced in a separate series
- svid will be used instead of the typec_mode_type enum

Andrei Kuchynski (5):
  usb: typec: Add alt_mode_override field to port property
  platform/chrome: cros_ec_typec: Set alt_mode_override flag
  usb: typec: ucsi: Set alt_mode_override flag
  usb: typec: Implement alternate mode priority handling
  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/Makefile                  |  2 +-
 drivers/usb/typec/class.c                   | 41 +++++++++++++++++++--
 drivers/usb/typec/class.h                   |  2 +
 drivers/usb/typec/mode_selection.c          | 38 +++++++++++++++++++
 drivers/usb/typec/mode_selection.h          |  6 +++
 drivers/usb/typec/ucsi/ucsi.c               |  2 +
 include/linux/usb/typec.h                   |  1 +
 include/linux/usb/typec_altmode.h           |  1 +
 10 files changed, 100 insertions(+), 5 deletions(-)
 create mode 100644 drivers/usb/typec/mode_selection.c
 create mode 100644 drivers/usb/typec/mode_selection.h

-- 
2.51.0.rc2.233.g662b1ed5c5-goog

[PATCH v2 1/5] usb: typec: Add alt_mode_override 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>
---
 drivers/usb/typec/class.c | 9 ++++++---
 drivers/usb/typec/class.h | 2 ++
 include/linux/usb/typec.h | 1 +
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
index 67a533e35150..9f86605ce125 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;
 }
@@ -2681,6 +2683,7 @@ 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..c53a04b9dc75 100644
--- a/drivers/usb/typec/class.h
+++ b/drivers/usb/typec/class.h
@@ -80,6 +80,8 @@ struct typec_port {
 	 */
 	struct device			*usb2_dev;
 	struct device			*usb3_dev;
+
+	bool				mode_control;
 };
 
 #define to_typec_port(_dev_) container_of(_dev_, struct typec_port, dev)
diff --git a/include/linux/usb/typec.h b/include/linux/usb/typec.h
index 252af3f77039..cbc94282e45e 100644
--- a/include/linux/usb/typec.h
+++ b/include/linux/usb/typec.h
@@ -304,6 +304,7 @@ 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;
-- 
2.51.0.rc2.233.g662b1ed5c5-goog

Re: [PATCH v2 1/5] usb: typec: Add alt_mode_override field to port property

[Heikki Krogerus]

On Mon, Aug 25, 2025 at 02:57:46PM +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>
> ---
>  drivers/usb/typec/class.c | 9 ++++++---
>  drivers/usb/typec/class.h | 2 ++
>  include/linux/usb/typec.h | 1 +
>  3 files changed, 9 insertions(+), 3 deletions(-)

This is okay by me, but you forgot to document the file.

thanks,

> diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
> index 67a533e35150..9f86605ce125 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;
>  }
> @@ -2681,6 +2683,7 @@ 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..c53a04b9dc75 100644
> --- a/drivers/usb/typec/class.h
> +++ b/drivers/usb/typec/class.h
> @@ -80,6 +80,8 @@ struct typec_port {
>  	 */
>  	struct device			*usb2_dev;
>  	struct device			*usb3_dev;
> +
> +	bool				mode_control;
>  };
>  
>  #define to_typec_port(_dev_) container_of(_dev_, struct typec_port, dev)
> diff --git a/include/linux/usb/typec.h b/include/linux/usb/typec.h
> index 252af3f77039..cbc94282e45e 100644
> --- a/include/linux/usb/typec.h
> +++ b/include/linux/usb/typec.h
> @@ -304,6 +304,7 @@ 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;
> -- 
> 2.51.0.rc2.233.g662b1ed5c5-goog
> 

-- 
heikki

Re: [PATCH v2 1/5] usb: typec: Add alt_mode_override field to port property

[Andrei Kuchynski]

On Fri, Sep 5, 2025 at 11:57 AM Heikki Krogerus
<heikki.krogerus@linux.intel.com> wrote:
>
> On Mon, Aug 25, 2025 at 02:57:46PM +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>
> > ---
> >  drivers/usb/typec/class.c | 9 ++++++---
> >  drivers/usb/typec/class.h | 2 ++
> >  include/linux/usb/typec.h | 1 +
> >  3 files changed, 9 insertions(+), 3 deletions(-)
>
> This is okay by me, but you forgot to document the file.
>
> thanks,

Hi Heikki,

I missed it.
Thanks!


Andrei

[PATCH v2 2/5] platform/chrome: cros_ec_typec: Set alt_mode_override 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>
---
 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)) {
-- 
2.51.0.rc2.233.g662b1ed5c5-goog

Re: [PATCH v2 2/5] platform/chrome: cros_ec_typec: Set alt_mode_override flag

[Heikki Krogerus]

On Mon, Aug 25, 2025 at 02:57:47PM +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>

> ---
>  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)) {
> -- 
> 2.51.0.rc2.233.g662b1ed5c5-goog
> 

-- 
heikki

[PATCH v2 3/5] usb: typec: ucsi: Set alt_mode_override 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 | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
index 0d6b0cf5a7cd..85a6b7fc6d93 100644
--- a/drivers/usb/typec/ucsi/ucsi.c
+++ b/drivers/usb/typec/ucsi/ucsi.c
@@ -1632,6 +1632,8 @@ 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->ops->update_connector)
 		ucsi->ops->update_connector(con);
-- 
2.51.0.rc2.233.g662b1ed5c5-goog

Re: [PATCH v2 3/5] usb: typec: ucsi: Set alt_mode_override flag

[Heikki Krogerus]

On Mon, Aug 25, 2025 at 02:57:48PM +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>
> ---
>  drivers/usb/typec/ucsi/ucsi.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
> index 0d6b0cf5a7cd..85a6b7fc6d93 100644
> --- a/drivers/usb/typec/ucsi/ucsi.c
> +++ b/drivers/usb/typec/ucsi/ucsi.c
> @@ -1632,6 +1632,8 @@ 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);

Fits to one.

thanks,

-- 
heikki

Re: [PATCH v2 3/5] usb: typec: ucsi: Set alt_mode_override flag

[Andrei Kuchynski]

On Fri, Sep 5, 2025 at 11:59 AM Heikki Krogerus
<heikki.krogerus@linux.intel.com> wrote:
>
> On Mon, Aug 25, 2025 at 02:57:48PM +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>
> > ---
> >  drivers/usb/typec/ucsi/ucsi.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
> > index 0d6b0cf5a7cd..85a6b7fc6d93 100644
> > --- a/drivers/usb/typec/ucsi/ucsi.c
> > +++ b/drivers/usb/typec/ucsi/ucsi.c
> > @@ -1632,6 +1632,8 @@ 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);
>
> Fits to one.
>
> thanks,
>
> --
> heikki

I miscalculated it. One line

Thanks,
Andrei

[PATCH v2 4/5] usb: typec: Implement alternate mode priority handling

[Andrei Kuchynski]

This patch introduces APIs to manage the priority of USB Type-C alternate
modes. These APIs allow for setting and retrieving a priority number for
each mode. 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>
---
 drivers/usb/typec/Makefile         |  2 +-
 drivers/usb/typec/mode_selection.c | 38 ++++++++++++++++++++++++++++++
 drivers/usb/typec/mode_selection.h |  6 +++++
 include/linux/usb/typec_altmode.h  |  1 +
 4 files changed, 46 insertions(+), 1 deletion(-)
 create mode 100644 drivers/usb/typec/mode_selection.c
 create mode 100644 drivers/usb/typec/mode_selection.h

diff --git a/drivers/usb/typec/Makefile b/drivers/usb/typec/Makefile
index 7a368fea61bc..8a6a1c663eb6 100644
--- a/drivers/usb/typec/Makefile
+++ b/drivers/usb/typec/Makefile
@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_TYPEC)		+= typec.o
-typec-y				:= class.o mux.o bus.o pd.o retimer.o
+typec-y				:= class.o mux.o bus.o pd.o retimer.o mode_selection.o
 typec-$(CONFIG_ACPI)		+= port-mapper.o
 obj-$(CONFIG_TYPEC)		+= altmodes/
 obj-$(CONFIG_TYPEC_TCPM)	+= tcpm/
diff --git a/drivers/usb/typec/mode_selection.c b/drivers/usb/typec/mode_selection.c
new file mode 100644
index 000000000000..2179bf25f5d4
--- /dev/null
+++ b/drivers/usb/typec/mode_selection.c
@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2025 Google LLC.
+ */
+
+#include "mode_selection.h"
+#include "class.h"
+#include "bus.h"
+
+static int increment_duplicated_priority(struct device *dev, void *data)
+{
+	struct typec_altmode **alt_target = (struct typec_altmode **)data;
+
+	if (is_typec_altmode(dev)) {
+		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;
+}
+
+void typec_mode_set_priority(struct typec_altmode *alt,
+		const unsigned int priority)
+{
+	struct typec_port *port = to_typec_port(alt->dev.parent);
+	int res = 1;
+
+	alt->priority = priority;
+
+	while (res)
+		res = device_for_each_child(&port->dev, &alt,
+				increment_duplicated_priority);
+}
diff --git a/drivers/usb/typec/mode_selection.h b/drivers/usb/typec/mode_selection.h
new file mode 100644
index 000000000000..cbf5a37e6404
--- /dev/null
+++ b/drivers/usb/typec/mode_selection.h
@@ -0,0 +1,6 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <linux/usb/typec_altmode.h>
+
+void typec_mode_set_priority(struct typec_altmode *alt,
+		const unsigned int priority);
diff --git a/include/linux/usb/typec_altmode.h b/include/linux/usb/typec_altmode.h
index b3c0866ea70f..571c6e00b54f 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;
+	unsigned int			priority;
 
 	char				*desc;
 	const struct typec_altmode_ops	*ops;
-- 
2.51.0.rc2.233.g662b1ed5c5-goog

Re: [PATCH v2 4/5] usb: typec: Implement alternate mode priority handling

[Heikki Krogerus]

On Mon, Aug 25, 2025 at 02:57:49PM +0000, Andrei Kuchynski wrote:
> This patch introduces APIs to manage the priority of USB Type-C alternate
> modes. These APIs allow for setting and retrieving a priority number for
> each mode. 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>
> ---
>  drivers/usb/typec/Makefile         |  2 +-
>  drivers/usb/typec/mode_selection.c | 38 ++++++++++++++++++++++++++++++
>  drivers/usb/typec/mode_selection.h |  6 +++++
>  include/linux/usb/typec_altmode.h  |  1 +
>  4 files changed, 46 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/usb/typec/mode_selection.c
>  create mode 100644 drivers/usb/typec/mode_selection.h
> 
> diff --git a/drivers/usb/typec/Makefile b/drivers/usb/typec/Makefile
> index 7a368fea61bc..8a6a1c663eb6 100644
> --- a/drivers/usb/typec/Makefile
> +++ b/drivers/usb/typec/Makefile
> @@ -1,6 +1,6 @@
>  # SPDX-License-Identifier: GPL-2.0
>  obj-$(CONFIG_TYPEC)		+= typec.o
> -typec-y				:= class.o mux.o bus.o pd.o retimer.o
> +typec-y				:= class.o mux.o bus.o pd.o retimer.o mode_selection.o
>  typec-$(CONFIG_ACPI)		+= port-mapper.o
>  obj-$(CONFIG_TYPEC)		+= altmodes/
>  obj-$(CONFIG_TYPEC_TCPM)	+= tcpm/
> diff --git a/drivers/usb/typec/mode_selection.c b/drivers/usb/typec/mode_selection.c
> new file mode 100644
> index 000000000000..2179bf25f5d4
> --- /dev/null
> +++ b/drivers/usb/typec/mode_selection.c
> @@ -0,0 +1,38 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright 2025 Google LLC.
> + */
> +
> +#include "mode_selection.h"
> +#include "class.h"
> +#include "bus.h"
> +
> +static int increment_duplicated_priority(struct device *dev, void *data)
> +{
> +	struct typec_altmode **alt_target = (struct typec_altmode **)data;
> +
> +	if (is_typec_altmode(dev)) {
> +		struct typec_altmode *alt = to_typec_altmode(dev);
> +
> +		if (alt != *alt_target && alt->priority == (*alt_target)->priority) {
> +			alt->priority++;
> +			*alt_target = alt;
> +			return 1;

Couldn't you just always return 0?

> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +void typec_mode_set_priority(struct typec_altmode *alt,
> +		const unsigned int priority)
> +{
> +	struct typec_port *port = to_typec_port(alt->dev.parent);
> +	int res = 1;
> +
> +	alt->priority = priority;
> +
> +	while (res)
> +		res = device_for_each_child(&port->dev, &alt,
> +				increment_duplicated_priority);

Then this could be:

        device_for_each_child(&port->dev, &alt, increment_duplicated_priority);

right?

> +}
> diff --git a/drivers/usb/typec/mode_selection.h b/drivers/usb/typec/mode_selection.h
> new file mode 100644
> index 000000000000..cbf5a37e6404
> --- /dev/null
> +++ b/drivers/usb/typec/mode_selection.h
> @@ -0,0 +1,6 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#include <linux/usb/typec_altmode.h>
> +
> +void typec_mode_set_priority(struct typec_altmode *alt,
> +		const unsigned int priority);
> diff --git a/include/linux/usb/typec_altmode.h b/include/linux/usb/typec_altmode.h
> index b3c0866ea70f..571c6e00b54f 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;
> +	unsigned int			priority;
>  
>  	char				*desc;
>  	const struct typec_altmode_ops	*ops;
> -- 
> 2.51.0.rc2.233.g662b1ed5c5-goog
> 

-- 
heikki

Re: [PATCH v2 4/5] usb: typec: Implement alternate mode priority handling

[Andrei Kuchynski]

On Fri, Sep 5, 2025 at 12:25 PM Heikki Krogerus
<heikki.krogerus@linux.intel.com> wrote:
>
> On Mon, Aug 25, 2025 at 02:57:49PM +0000, Andrei Kuchynski wrote:
> > This patch introduces APIs to manage the priority of USB Type-C alternate
> > modes. These APIs allow for setting and retrieving a priority number for
> > each mode. 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>
> > ---
> >  drivers/usb/typec/Makefile         |  2 +-
> >  drivers/usb/typec/mode_selection.c | 38 ++++++++++++++++++++++++++++++
> >  drivers/usb/typec/mode_selection.h |  6 +++++
> >  include/linux/usb/typec_altmode.h  |  1 +
> >  4 files changed, 46 insertions(+), 1 deletion(-)
> >  create mode 100644 drivers/usb/typec/mode_selection.c
> >  create mode 100644 drivers/usb/typec/mode_selection.h
> >
> > diff --git a/drivers/usb/typec/Makefile b/drivers/usb/typec/Makefile
> > index 7a368fea61bc..8a6a1c663eb6 100644
> > --- a/drivers/usb/typec/Makefile
> > +++ b/drivers/usb/typec/Makefile
> > @@ -1,6 +1,6 @@
> >  # SPDX-License-Identifier: GPL-2.0
> >  obj-$(CONFIG_TYPEC)          += typec.o
> > -typec-y                              := class.o mux.o bus.o pd.o retimer.o
> > +typec-y                              := class.o mux.o bus.o pd.o retimer.o mode_selection.o
> >  typec-$(CONFIG_ACPI)         += port-mapper.o
> >  obj-$(CONFIG_TYPEC)          += altmodes/
> >  obj-$(CONFIG_TYPEC_TCPM)     += tcpm/
> > diff --git a/drivers/usb/typec/mode_selection.c b/drivers/usb/typec/mode_selection.c
> > new file mode 100644
> > index 000000000000..2179bf25f5d4
> > --- /dev/null
> > +++ b/drivers/usb/typec/mode_selection.c
> > @@ -0,0 +1,38 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Copyright 2025 Google LLC.
> > + */
> > +
> > +#include "mode_selection.h"
> > +#include "class.h"
> > +#include "bus.h"
> > +
> > +static int increment_duplicated_priority(struct device *dev, void *data)
> > +{
> > +     struct typec_altmode **alt_target = (struct typec_altmode **)data;
> > +
> > +     if (is_typec_altmode(dev)) {
> > +             struct typec_altmode *alt = to_typec_altmode(dev);
> > +
> > +             if (alt != *alt_target && alt->priority == (*alt_target)->priority) {
> > +                     alt->priority++;
> > +                     *alt_target = alt;
> > +                     return 1;
>
> Couldn't you just always return 0?
>

Priority values for each mode are consistently unique, eliminating the need
for further processing if a duplicate is found.

> > +             }
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> > +void typec_mode_set_priority(struct typec_altmode *alt,
> > +             const unsigned int priority)
> > +{
> > +     struct typec_port *port = to_typec_port(alt->dev.parent);
> > +     int res = 1;
> > +
> > +     alt->priority = priority;
> > +
> > +     while (res)
> > +             res = device_for_each_child(&port->dev, &alt,
> > +                             increment_duplicated_priority);
>
> Then this could be:
>
>         device_for_each_child(&port->dev, &alt, increment_duplicated_priority);
>
> right?
>

Unfortunately, the child's list is not in prioritized order. When a
duplicated value is found, the cycle should start for the whole list again.
I definitely need a loop here.

Thanks,
Andrei

[PATCH v2 5/5] 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.

Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
---
 Documentation/ABI/testing/sysfs-class-typec | 11 +++++++
 drivers/usb/typec/class.c                   | 32 ++++++++++++++++++++-
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-class-typec b/Documentation/ABI/testing/sysfs-class-typec
index 38e101c17a00..dab3e4e727b6 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 alt-mode.
+		When read, it shows the current integer priority value. Lower numerical
+		values indicate higher priority (0 is the highest priority).
+		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 9f86605ce125..aaab2e1e98b4 100644
--- a/drivers/usb/typec/class.c
+++ b/drivers/usb/typec/class.c
@@ -19,6 +19,7 @@
 #include "bus.h"
 #include "class.h"
 #include "pd.h"
+#include "mode_selection.h"
 
 static DEFINE_IDA(typec_index_ida);
 
@@ -445,11 +446,34 @@ svid_show(struct device *dev, struct device_attribute *attr, char *buf)
 }
 static DEVICE_ATTR_RO(svid);
 
+static ssize_t priority_store(struct device *dev,
+			       struct device_attribute *attr,
+			       const char *buf, size_t size)
+{
+	unsigned int val;
+	int err = kstrtouint(buf, 10, &val);
+
+	if (!err) {
+		typec_mode_set_priority(to_typec_altmode(dev), val);
+		return size;
+	}
+
+	return err;
+}
+
+static ssize_t priority_show(struct device *dev,
+			      struct device_attribute *attr, char *buf)
+{
+	return sprintf(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 +483,15 @@ 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;
 }
@@ -2491,6 +2519,8 @@ typec_port_register_altmode(struct typec_port *port,
 		to_altmode(adev)->retimer = retimer;
 	}
 
+	typec_mode_set_priority(adev, 0);
+
 	return adev;
 }
 EXPORT_SYMBOL_GPL(typec_port_register_altmode);
-- 
2.51.0.rc2.233.g662b1ed5c5-goog

Re: [PATCH v2 5/5] usb: typec: Expose alternate mode priority via sysfs

[Heikki Krogerus]

On Mon, Aug 25, 2025 at 02:57:50PM +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.
> 
> Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
> ---
>  Documentation/ABI/testing/sysfs-class-typec | 11 +++++++
>  drivers/usb/typec/class.c                   | 32 ++++++++++++++++++++-

Maybe patch 4/5 could be squashed into this patch, and I'm wondering
would it make sense to just keep the typec_mode_set_priority() in this
file (drivers/usb/typec/class.c).

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

>  2 files changed, 42 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-typec b/Documentation/ABI/testing/sysfs-class-typec
> index 38e101c17a00..dab3e4e727b6 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 alt-mode.
> +		When read, it shows the current integer priority value. Lower numerical
> +		values indicate higher priority (0 is the highest priority).
> +		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 9f86605ce125..aaab2e1e98b4 100644
> --- a/drivers/usb/typec/class.c
> +++ b/drivers/usb/typec/class.c
> @@ -19,6 +19,7 @@
>  #include "bus.h"
>  #include "class.h"
>  #include "pd.h"
> +#include "mode_selection.h"
>  
>  static DEFINE_IDA(typec_index_ida);
>  
> @@ -445,11 +446,34 @@ svid_show(struct device *dev, struct device_attribute *attr, char *buf)
>  }
>  static DEVICE_ATTR_RO(svid);
>  
> +static ssize_t priority_store(struct device *dev,
> +			       struct device_attribute *attr,
> +			       const char *buf, size_t size)
> +{
> +	unsigned int val;
> +	int err = kstrtouint(buf, 10, &val);
> +
> +	if (!err) {
> +		typec_mode_set_priority(to_typec_altmode(dev), val);
> +		return size;
> +	}
> +
> +	return err;
> +}
> +
> +static ssize_t priority_show(struct device *dev,
> +			      struct device_attribute *attr, char *buf)
> +{
> +	return sprintf(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 +483,15 @@ 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;
>  }
> @@ -2491,6 +2519,8 @@ typec_port_register_altmode(struct typec_port *port,
>  		to_altmode(adev)->retimer = retimer;
>  	}
>  
> +	typec_mode_set_priority(adev, 0);
> +
>  	return adev;
>  }
>  EXPORT_SYMBOL_GPL(typec_port_register_altmode);
> -- 
> 2.51.0.rc2.233.g662b1ed5c5-goog
> 

-- 
heikki

Re: [PATCH v2 5/5] usb: typec: Expose alternate mode priority via sysfs

[Andrei Kuchynski]

On Fri, Sep 5, 2025 at 12:34 PM Heikki Krogerus
<heikki.krogerus@linux.intel.com> wrote:
>
> On Mon, Aug 25, 2025 at 02:57:50PM +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.
> >
> > Signed-off-by: Andrei Kuchynski <akuchynski@chromium.org>
> > ---
> >  Documentation/ABI/testing/sysfs-class-typec | 11 +++++++
> >  drivers/usb/typec/class.c                   | 32 ++++++++++++++++++++-
>
> Maybe patch 4/5 could be squashed into this patch, and I'm wondering
> would it make sense to just keep the typec_mode_set_priority() in this
> file (drivers/usb/typec/class.c).
>
> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
>
> --
> heikki

You're right, mode_selection.c is quite empty now. However, in the next
series, it will be the only user of the priority variable. So I'd prefer to
keep it there, if you don’t mind.
I think putting it in class.c would create a mess.

Thank you for the review!

Andrei

Re: [PATCH v2 0/5] USB Type-C alternate mode priorities

[Heikki Krogerus]

Hi Andrei,

On Mon, Aug 25, 2025 at 02:57:45PM +0000, Andrei Kuchynski wrote:
> 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 6.16.
> 
> Changes in v2:
> - The priority variable is now a member of the typec_altmode struct
> - typec_altmode2port is used to obtain the typec_port struct pointer
> - Default priorities are now set based on the order of registration
> - The mode_control capability is enabled by default
> - The mode_selection_state struct will be introduced in a separate series
> - svid will be used instead of the typec_mode_type enum
> 
> Andrei Kuchynski (5):
>   usb: typec: Add alt_mode_override field to port property
>   platform/chrome: cros_ec_typec: Set alt_mode_override flag
>   usb: typec: ucsi: Set alt_mode_override flag
>   usb: typec: Implement alternate mode priority handling
>   usb: typec: Expose alternate mode priority via sysfs

I'm sorry for keeping you waiting. I think these are okay - although,
I had to put a few nitpicks :) but they are minor - but can you
include a patch where you use the priority member in a driver (maybe
cros_ec_typec.c)?

thanks,

-- 
heikki

Re: [PATCH v2 0/5] USB Type-C alternate mode priorities

[Andrei Kuchynski]

On Fri, Sep 5, 2025 at 1:57 PM Heikki Krogerus
<heikki.krogerus@linux.intel.com> wrote:
>
> Hi Andrei,
>
> On Mon, Aug 25, 2025 at 02:57:45PM +0000, Andrei Kuchynski wrote:
> > 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 6.16.
> >
> > Changes in v2:
> > - The priority variable is now a member of the typec_altmode struct
> > - typec_altmode2port is used to obtain the typec_port struct pointer
> > - Default priorities are now set based on the order of registration
> > - The mode_control capability is enabled by default
> > - The mode_selection_state struct will be introduced in a separate series
> > - svid will be used instead of the typec_mode_type enum
> >
> > Andrei Kuchynski (5):
> >   usb: typec: Add alt_mode_override field to port property
> >   platform/chrome: cros_ec_typec: Set alt_mode_override flag
> >   usb: typec: ucsi: Set alt_mode_override flag
> >   usb: typec: Implement alternate mode priority handling
> >   usb: typec: Expose alternate mode priority via sysfs
>
> I'm sorry for keeping you waiting. I think these are okay - although,
> I had to put a few nitpicks :) but they are minor - but can you
> include a patch where you use the priority member in a driver (maybe
> cros_ec_typec.c)?
>
> thanks,
>
> --
> heikki

Thank you for your review and feedback! I appreciate you taking the time to
provide these notes.

The patch using the priority member is part of a subsequent series that I
have ready. I will send it shortly. This functionality is implemented in
mode_selection.c to determine the mode order, and we plan to use it for
both the cros_ec_typec and UCSI implementations.

I will send a new v3 patch set shortly with the minor changes you suggested.

Thanks!
Andrei