What:  Raise a uevent when a USB charger is inserted or removed
Date:  2020-01-14
KernelVersion: 5.6
Contact: linux-usb@vger.kernel.org
Description: There are two USB charger states:

  - USB_CHARGER_ABSENT
  - USB_CHARGER_PRESENT

  There are five USB charger types:

  ========================  ==========================
  USB_CHARGER_UNKNOWN_TYPE  Charger type is unknown
  USB_CHARGER_SDP_TYPE      Standard Downstream Port
  USB_CHARGER_CDP_TYPE      Charging Downstream Port
  USB_CHARGER_DCP_TYPE      Dedicated Charging Port
  USB_CHARGER_ACA_TYPE      Accessory Charging Adapter
  ========================  ==========================

  https://www.usb.org/document-library/battery-charging-v12-spec-and-adopters-agreement

  Here are two examples taken using ``udevadm monitor -p`` when
  USB charger is online::

      UDEV  change   /devices/soc0/usbphynop1 (platform)
      ACTION=change
      DEVPATH=/devices/soc0/usbphynop1
      DRIVER=usb_phy_generic
      MODALIAS=of:Nusbphynop1T(null)Cusb-nop-xceiv
      OF_COMPATIBLE_0=usb-nop-xceiv
      OF_COMPATIBLE_N=1
      OF_FULLNAME=/usbphynop1
      OF_NAME=usbphynop1
      SEQNUM=2493
      SUBSYSTEM=platform
      USB_CHARGER_STATE=USB_CHARGER_PRESENT
      USB_CHARGER_TYPE=USB_CHARGER_SDP_TYPE
      USEC_INITIALIZED=227422826

  USB charger is offline::

      KERNEL change   /devices/soc0/usbphynop1 (platform)
      ACTION=change
      DEVPATH=/devices/soc0/usbphynop1
      DRIVER=usb_phy_generic
      MODALIAS=of:Nusbphynop1T(null)Cusb-nop-xceiv
      OF_COMPATIBLE_0=usb-nop-xceiv
      OF_COMPATIBLE_N=1
      OF_FULLNAME=/usbphynop1
      OF_NAME=usbphynop1
      SEQNUM=2494
      SUBSYSTEM=platform
      USB_CHARGER_STATE=USB_CHARGER_ABSENT
      USB_CHARGER_TYPE=USB_CHARGER_UNKNOWN_TYPE