On Sun, Dec 11, 2022 at 11:37:55AM -0800, Badhri Jagan Sridharan wrote:
> Exporsing HotPlugDetect(HPD) helps userspace to infer HPD
> state as defined by VESA DisplayPort Alt Mode on USB Type-C Standard.
> This allows userspace to notify users for self help, for instance,
> to hint user that the display port cable is probably detached (or)
> the display port sink (viz., monitors ect.,) is un-powered.
> Also helps to debug issues reported from field.
>
> This change adds an additional attribute "hpd" to the existing
> "displayport" attributes.
>
> VESA DisplayPort Alt Mode on USB Type-C Standard defines how
> HotPlugDetect(HPD) shall be supported on the USB-C connector
> when operating in DisplayPort Alt Mode. This is a read only
> node which reflects the current state of HPD.
>
> Valid values:
> - 1 when HPD’s logical state is high (HPD_High)
> - 0 when HPD’s logical state is low (HPD_Low)
>
> Signed-off-by: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
Reviewed-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> ---
> .../ABI/testing/sysfs-driver-typec-displayport | 15 +++++++++++++++
> drivers/usb/typec/altmodes/displayport.c | 10 ++++++++++
> 2 files changed, 25 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-driver-typec-displayport b/Documentation/ABI/testing/sysfs-driver-typec-displayport
> index 231471ad0d4b..256c87c5219a 100644
> --- a/Documentation/ABI/testing/sysfs-driver-typec-displayport
> +++ b/Documentation/ABI/testing/sysfs-driver-typec-displayport
> @@ -47,3 +47,18 @@ Description:
> USB SuperSpeed protocol. From user perspective pin assignments C
> and E are equal, where all channels on the connector are used
> for carrying DisplayPort protocol (allowing higher resolutions).
> +
> +What: /sys/bus/typec/devices/.../displayport/hpd
> +Date: Dec 2022
> +Contact: Badhri Jagan Sridharan <badhri@xxxxxxxxxx>
> +Description:
> + VESA DisplayPort Alt Mode on USB Type-C Standard defines how
> + HotPlugDetect(HPD) shall be supported on the USB-C connector when
> + operating in DisplayPort Alt Mode. This is a read only node which
> + reflects the current state of HPD.
> +
> + Valid values:
> + - 1: when HPD’s logical state is high (HPD_High) as defined
> + by VESA DisplayPort Alt Mode on USB Type-C Standard.
> + - 0 when HPD’s logical state is low (HPD_Low) as defined by
> + VESA DisplayPort Alt Mode on USB Type-C Standard.
> diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c
> index de66a2949e33..06fb4732f8cd 100644
> --- a/drivers/usb/typec/altmodes/displayport.c
> +++ b/drivers/usb/typec/altmodes/displayport.c
> @@ -146,6 +146,7 @@ static int dp_altmode_status_update(struct dp_altmode *dp)
> if (dp->hpd != hpd) {
> drm_connector_oob_hotplug_event(dp->connector_fwnode);
> dp->hpd = hpd;
> + sysfs_notify(&dp->alt->dev.kobj, "displayport", "hpd");
> }
> }
>
> @@ -508,9 +509,18 @@ static ssize_t pin_assignment_show(struct device *dev,
> }
> static DEVICE_ATTR_RW(pin_assignment);
>
> +static ssize_t hpd_show(struct device *dev, struct device_attribute *attr, char *buf)
> +{
> + struct dp_altmode *dp = dev_get_drvdata(dev);
> +
> + return sysfs_emit(buf, "%d\n", dp->hpd);
> +}
> +static DEVICE_ATTR_RO(hpd);
> +
> static struct attribute *dp_altmode_attrs[] = {
> &dev_attr_configuration.attr,
> &dev_attr_pin_assignment.attr,
> + &dev_attr_hpd.attr,
> NULL
> };
>
>
> base-commit: 81c25247a2a03a0f97e4805d7aff7541ccff6baa
> --
> 2.39.0.rc1.256.g54fd8350bd-goog
thanks,
--
heikki
