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Date: Tue, 17 Nov 2020 14:41:43 +0200
From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To: Prashant Malani <pmalani@...omium.org>
Cc: linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
gregkh@...uxfoundation.org, enric.balletbo@...labora.com
Subject: Re: [PATCH v3 03/11] usb: typec: Add plug num_altmodes sysfs attr
On Mon, Nov 16, 2020 at 12:11:42PM -0800, Prashant Malani wrote:
> Add a field to the typec_plug struct to record the number of available
> altmodes as well as the corresponding sysfs attribute to expose this to
> userspace.
>
> This allows userspace to determine whether there are any
> remaining alternate modes left to be registered by the kernel driver. It
> can begin executing any policy state machine after all available
> alternate modes have been registered with the connector class framework.
>
> This value is set to "-1" initially, signifying that a valid number of
> alternate modes haven't been set for the plug. The sysfs file remains
> hidden as long as the attribute value is -1.
Why couldn't we just keep it hidden for as long as the number of
alt modes is 0? If you already explained that, then I apologise, I've
forgotten.
> We re-use the partner attribute for number_of_alternate_modes since the
> usage and name is similar, and update the corresponding *_show() command
> to support both partner and plugs.
>
> Signed-off-by: Prashant Malani <pmalani@...omium.org>
> ---
>
> Changes in v3:
> - Re-arranged patch order and combined it with related series of
> patches.
>
> No version v2.
>
> Documentation/ABI/testing/sysfs-class-typec | 9 +++
> drivers/usb/typec/class.c | 77 ++++++++++++++++++++-
> include/linux/usb/typec.h | 1 +
> 3 files changed, 85 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-class-typec b/Documentation/ABI/testing/sysfs-class-typec
> index 73ac7b461ae5..29eccf5fb8ed 100644
> --- a/Documentation/ABI/testing/sysfs-class-typec
> +++ b/Documentation/ABI/testing/sysfs-class-typec
> @@ -204,6 +204,15 @@ Description:
> - type-c
> - captive
>
> +What: /sys/class/typec/<port>-<plug>/number_of_alternate_modes
> +Date: November 2020
> +Contact: Prashant Malani <pmalani@...omium.org>
> +Description:
> + Shows the number of alternate modes which are advertised by the plug
> + associated with a particular cable during Power Delivery discovery.
> + This file remains hidden until a value greater than or equal to 0
> + is set by Type C port driver.
> +
> What: /sys/class/typec/<port>-cable/identity/
> Date: April 2017
> Contact: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> diff --git a/drivers/usb/typec/class.c b/drivers/usb/typec/class.c
> index c7412ddbd311..e68798599ca8 100644
> --- a/drivers/usb/typec/class.c
> +++ b/drivers/usb/typec/class.c
> @@ -18,6 +18,7 @@ struct typec_plug {
> struct device dev;
> enum typec_plug_index index;
> struct ida mode_ids;
> + int num_altmodes;
> };
>
> struct typec_cable {
> @@ -536,9 +537,21 @@ static DEVICE_ATTR_RO(supports_usb_power_delivery);
> static ssize_t number_of_alternate_modes_show(struct device *dev, struct device_attribute *attr,
> char *buf)
> {
> - struct typec_partner *p = to_typec_partner(dev);
> + struct typec_partner *partner;
> + struct typec_plug *plug;
> + int num_altmodes;
> +
> + if (is_typec_partner(dev)) {
> + partner = to_typec_partner(dev);
> + num_altmodes = partner->num_altmodes;
> + } else if (is_typec_plug(dev)) {
> + plug = to_typec_plug(dev);
> + num_altmodes = plug->num_altmodes;
> + } else {
> + return 0;
> + }
>
> - return sysfs_emit(buf, "%d\n", p->num_altmodes);
> + return sysfs_emit(buf, "%d\n", num_altmodes);
> }
> static DEVICE_ATTR_RO(number_of_alternate_modes);
>
> @@ -726,11 +739,70 @@ static void typec_plug_release(struct device *dev)
> kfree(plug);
> }
>
> +static struct attribute *typec_plug_attrs[] = {
> + &dev_attr_number_of_alternate_modes.attr,
> + NULL
> +};
> +
> +static umode_t typec_plug_attr_is_visible(struct kobject *kobj, struct attribute *attr, int n)
> +{
> + struct typec_plug *plug = to_typec_plug(kobj_to_dev(kobj));
> +
> + if (attr == &dev_attr_number_of_alternate_modes.attr) {
> + if (plug->num_altmodes < 0)
> + return 0;
> + }
> +
> + return attr->mode;
> +}
> +
> +static struct attribute_group typec_plug_group = {
> + .is_visible = typec_plug_attr_is_visible,
> + .attrs = typec_plug_attrs
> +};
> +
> +static const struct attribute_group *typec_plug_groups[] = {
> + &typec_plug_group,
> + NULL
> +};
> +
> static const struct device_type typec_plug_dev_type = {
> .name = "typec_plug",
> + .groups = typec_plug_groups,
> .release = typec_plug_release,
> };
>
> +/**
> + * typec_plug_set_num_altmodes - Set the number of available plug altmodes
> + * @plug: The plug to be updated.
> + * @num_altmodes: The number of altmodes we want to specify as available.
> + *
> + * This routine is used to report the number of alternate modes supported by the
> + * plug. This value is *not* enforced in alternate mode registration routines.
> + *
> + * @plug.num_altmodes is set to -1 on plug registration, denoting that
> + * a valid value has not been set for it yet.
> + *
> + * Returns 0 on success or negative error number on failure.
> + */
> +int typec_plug_set_num_altmodes(struct typec_plug *plug, int num_altmodes)
> +{
> + int ret;
> +
> + if (num_altmodes < 0)
> + return -EINVAL;
> +
> + plug->num_altmodes = num_altmodes;
> + ret = sysfs_update_group(&plug->dev.kobj, &typec_plug_group);
> + if (ret < 0)
> + return ret;
> +
> + sysfs_notify(&plug->dev.kobj, NULL, "number_of_alternate_modes");
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(typec_plug_set_num_altmodes);
> +
> /**
> * typec_plug_register_altmode - Register USB Type-C Cable Plug Alternate Mode
> * @plug: USB Type-C Cable Plug that supports the alternate mode
> @@ -776,6 +848,7 @@ struct typec_plug *typec_register_plug(struct typec_cable *cable,
> sprintf(name, "plug%d", desc->index);
>
> ida_init(&plug->mode_ids);
> + plug->num_altmodes = -1;
> plug->index = desc->index;
> plug->dev.class = typec_class;
> plug->dev.parent = &cable->dev;
> diff --git a/include/linux/usb/typec.h b/include/linux/usb/typec.h
> index bc6b1a71cb8a..54475323f83b 100644
> --- a/include/linux/usb/typec.h
> +++ b/include/linux/usb/typec.h
> @@ -130,6 +130,7 @@ int typec_partner_set_num_altmodes(struct typec_partner *partner, int num_altmod
> struct typec_altmode
> *typec_partner_register_altmode(struct typec_partner *partner,
> const struct typec_altmode_desc *desc);
> +int typec_plug_set_num_altmodes(struct typec_plug *plug, int num_altmodes);
> struct typec_altmode
> *typec_plug_register_altmode(struct typec_plug *plug,
> const struct typec_altmode_desc *desc);
> --
> 2.29.2.299.gdc1121823c-goog
thanks,
--
heikki
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