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

[Heikki Krogerus <heikki.krogerus@linux.intel.com>]

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