Re: [PATCH v3 5/5] usb: typec: Expose alternate mode priority via sysfs

Greg Kroah-Hartman
2025-09-10T13:28:01Z

On Fri, Sep 05, 2025 at 02:22:06PM +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>
> Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> ---
> 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.

What is the units here? 0 is highest, what is the lowest? What is the
range here? I can't determine this from the text, sorry.

> +
> 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);

For new sysfs files, please use sysfs_emit(), otherwise someone will
come along with a janitorial patch to fix it up after it lands in the
tree :)

thanks,

greg k-h