Re: [PATCH] usb: typec: Add num_altmodes partner attribute

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

On Tue, Jun 30, 2020 at 05:31:48PM -0700, Prashant Malani wrote:
> Add a user-visible attribute for the number of alt modes available in a
> partner. This allows userspace to determine whether there are any
> remaining alt modes left to be registered by the kernel driver. It can
> begin implementing any policy state machine after all available alt
> modes have been registered with the connector class framework.
> 
> This value is set to "-1" initially, which is an invalid value,
> signifying that a valid number of alt modes haven't been set for the
> partner.
> 
> Signed-off-by: Prashant Malani <pmalani@chromium.org>
> Cc: Benson Leung <bleung@chromium.org>
> ---
>  drivers/usb/typec/class.c | 34 ++++++++++++++++++++++++++++++++++
>  include/linux/usb/typec.h |  1 +
>  2 files changed, 35 insertions(+)
> 
> diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
> index c9234748537a..680cbcfbd427 100644
> --- a/drivers/usb/typec/class.c
> +++ b/drivers/usb/typec/class.c
> @@ -33,6 +33,7 @@ struct typec_partner {
>  	struct usb_pd_identity		*identity;
>  	enum typec_accessory		accessory;
>  	struct ida			mode_ids;
> +	int				num_altmodes;
>  };
>  
>  struct typec_port {
> @@ -532,9 +533,18 @@ static ssize_t supports_usb_power_delivery_show(struct device *dev,
>  }
>  static DEVICE_ATTR_RO(supports_usb_power_delivery);
>  
> +static ssize_t num_altmodes_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> +	struct typec_partner *p = to_typec_partner(dev);
> +
> +	return sprintf(buf, "%d\n", p->num_altmodes);
> +}
> +static DEVICE_ATTR_RO(num_altmodes);
> +
>  static struct attribute *typec_partner_attrs[] = {
>  	&dev_attr_accessory_mode.attr,
>  	&dev_attr_supports_usb_power_delivery.attr,
> +	&dev_attr_num_altmodes.attr,
>  	NULL
>  };
>  ATTRIBUTE_GROUPS(typec_partner);
> @@ -570,6 +580,29 @@ int typec_partner_set_identity(struct typec_partner *partner)
>  }
>  EXPORT_SYMBOL_GPL(typec_partner_set_identity);
>  
> +/**
> + * typec_partner_set_num_altmodes - Update number of available altmodes
> + * @partner: The partner to be updated
> + * @num_alt_modes: The number of altmodes we want to specify as available
> + *
> + * This routine is used to report the number of alternate modes supported by the
> + * partner. This value is *not* enforced in alt mode registration routines.
> + *
> + * @partner.num_altmodes is set to -1 on partner registration, denoting that
> + * a valid value has not been set for it yet.
> + */
> +int typec_partner_set_num_altmodes(struct typec_partner *partner, int num_altmodes)
> +{
> +	if (num_altmodes < 0)
> +		return -EINVAL;
> +
> +	partner->num_altmodes = num_altmodes;
> +	sysfs_notify(&partner->dev.kobj, NULL, "num_altmodes");
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(typec_partner_set_num_altmodes);

Who is calling this?  We need a user before we can add a newly exported
function.

thanks,

greg k-h