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.
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 <[email protected]>
---
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 <[email protected]>
+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 <[email protected]>
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
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 <[email protected]>
> ---
>
> 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 <[email protected]>
> +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 <[email protected]>
> 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
Hi Heikki,
On Tue, Nov 17, 2020 at 02:41:43PM +0200, Heikki Krogerus wrote:
> 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.
>
No worries :)
Succinctly, because 0 is a valid value for "number of altmodes
supported".
If we keep the attribute hidden for 0, then there won't
be a way for userspace to determine that PD discovery is done and we
don't expect any more cable plug altmodes to be registered by the kernel
Type C port driver (it can determine this by comparing
"number_of_altmodes" against the actual number of alt modes registered
by the Type C port driver).
If we keep "number_of_altmodes" hidden even for 0, the userspace cannot
differentiate between "this cable doesn't support any altmodes" and
"it does altmodes, but the PD stack hasn't completed PD Discovery
including DiscoverIdentity yet".
For reference, here is the initial patch and mini-discussion around it
back in July for port-partner altmodes [1] (I've followed a similar
logic here).
Hope this helps the rationale a bit more.
Best regards,
-Prashant
[1]:
https://lore.kernel.org/linux-usb/[email protected]/
On Tue, Nov 17, 2020 at 09:40:16AM -0800, Prashant Malani wrote:
> Hi Heikki,
>
> On Tue, Nov 17, 2020 at 02:41:43PM +0200, Heikki Krogerus wrote:
> > 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.
> >
>
> No worries :)
>
> Succinctly, because 0 is a valid value for "number of altmodes
> supported".
>
> If we keep the attribute hidden for 0, then there won't
> be a way for userspace to determine that PD discovery is done and we
> don't expect any more cable plug altmodes to be registered by the kernel
> Type C port driver (it can determine this by comparing
> "number_of_altmodes" against the actual number of alt modes registered
> by the Type C port driver).
>
> If we keep "number_of_altmodes" hidden even for 0, the userspace cannot
> differentiate between "this cable doesn't support any altmodes" and
> "it does altmodes, but the PD stack hasn't completed PD Discovery
> including DiscoverIdentity yet".
>
> For reference, here is the initial patch and mini-discussion around it
> back in July for port-partner altmodes [1] (I've followed a similar
> logic here).
>
> Hope this helps the rationale a bit more.
Got it. Thanks for the explanation (again :-).
Reviewed-by: Heikki Krogerus <[email protected]>
> Best regards,
>
> -Prashant
>
> [1]:
> https://lore.kernel.org/linux-usb/[email protected]/
thanks,
--
heikki