Re: [PATCH v3 2/4] usb: typec: Add attribute file showing the USB Modes of the partner

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Fri, Oct 11, 2024 at 03:44:00PM +0300, Heikki Krogerus wrote:
> This attribute file shows the supported USB modes (USB 2.0,
> USB 3.0 and USB4) of the partner, and the currently active
> mode.
> 
> The active mode is determined primarily by checking the
> speed of the enumerated USB device. When USB Power Delivery
> is supported, the active USB mode should be always the mode
> that was used with the Enter_USB Message, regardless of the
> result of the USB enumeration. The port drivers can
> separately assign the mode with a dedicated API.
> 
> If USB Power Delivery Identity is supplied for the partner
> device, the supported modes are extracted from it.
> 
> Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
> ---
>  Documentation/ABI/testing/sysfs-class-typec |  14 +++
>  drivers/usb/typec/class.c                   | 123 +++++++++++++++++++-
>  drivers/usb/typec/class.h                   |   2 +
>  include/linux/usb/typec.h                   |   5 +
>  4 files changed, 140 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-typec b/Documentation/ABI/testing/sysfs-class-typec
> index 7c307f02d99e..a3afe04b2688 100644
> --- a/Documentation/ABI/testing/sysfs-class-typec
> +++ b/Documentation/ABI/testing/sysfs-class-typec
> @@ -233,6 +233,20 @@ Description:
>  		directory exists, it will have an attribute file for every VDO
>  		in Discover Identity command result.
>  
> +What:		/sys/class/typec/<port>-partner/usb_mode
> +Date:		February 2024

It's later than this :)


> +Contact:	Heikki Krogerus <heikki.krogerus@linux.intel.com>
> +Description:	The USB Modes that the partner device supports. The active mode
> +		is displayed in brackets. The active USB mode can be changed by
> +		writing to this file when the port driver is able to send Data
> +		Reset Message to the partner. That requires USB Power Delivery
> +		contract between the partner and the port.
> +
> +		Valid values:
> +		- usb2 (USB 2.0)
> +		- usb3 (USB 3.2)
> +		- usb4 (USB4)

We should probably add all of this info to 'lsusb' one of these days.
I'll add it to my todo list...

> +
>  USB Type-C cable devices (eg. /sys/class/typec/port0-cable/)
>  
>  Note: Electronically Marked Cables will have a device also for one cable plug
> diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
> index ea9ee47bb246..a6fedafc9c86 100644
> --- a/drivers/usb/typec/class.c
> +++ b/drivers/usb/typec/class.c
> @@ -618,6 +618,74 @@ EXPORT_SYMBOL_GPL(typec_unregister_altmode);
>  /* ------------------------------------------------------------------------- */
>  /* Type-C Partners */
>  
> +/**
> + * typec_partner_set_usb_mode - Assign active USB Mode for the partner
> + * @partner: USB Type-C partner
> + * @mode: USB Mode (USB2, USB3 or USB4)
> + *
> + * The port drivers can use this function to assign the active USB Mode to
> + * @partner. The USB Mode can change for example due to Data Reset.
> + */
> +void typec_partner_set_usb_mode(struct typec_partner *partner, enum usb_mode mode)
> +{
> +	if (!partner || partner->usb_mode == mode)
> +		return;
> +
> +	partner->usb_capability |= BIT(mode - 1);
> +	partner->usb_mode = mode;
> +	sysfs_notify(&partner->dev.kobj, NULL, "usb_mode");

Who is listening for this and what are they going to do with the
information?

> +}
> +EXPORT_SYMBOL_GPL(typec_partner_set_usb_mode);
> +
> +static ssize_t
> +usb_mode_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	struct typec_partner *partner = to_typec_partner(dev);
> +	int len = 0;
> +	int i;
> +
> +	for (i = USB_MODE_USB2; i < USB_MODE_USB4 + 1; i++) {
> +		if (!(BIT(i - 1) & partner->usb_capability))
> +			continue;
> +
> +		if (i == partner->usb_mode)
> +			len += sysfs_emit_at(buf, len, "[%s] ", usb_modes[i]);
> +		else
> +			len += sysfs_emit_at(buf, len, "%s ", usb_modes[i]);
> +	}
> +
> +	buf[len - 1] = '\n';

Again, sysfs_emit_at()?

thanks,

greg k-h