platform/x86: thinkpad_acpi: Add USB-C Security (USCS) support

Newer ThinkPad systems expose a USB-C Security (Restricted Mode) feature.
When active, USB-C data connections are disabled while power delivery is
preserved. This is useful for kiosk and physically-secured deployments.

Hardware interface:

The HKEY device exposes a read-only ACPI method USCS():

  Return value bit layout:
    Bit 16 : Capability flag (1 = feature present on this SKU)
    Bit  0 : Current state  (0 = security OFF, 1 = security ON)

The sysfs attribute is read-only.

The Fn+U followed by Fn+S hotkey chord is the only way to toggle the
hardware state.

Hotkey:

Fn+U followed by Fn+S generates HKEY event 0x131e.

sysfs interface:

  /sys/devices/platform/thinkpad_acpi/usb_c_security  (read-only)
  "enabled\n"  -- data connections are currently blocked
  "disabled\n" -- data connections are currently allowed

  The attribute is hidden on SKUs where the USCS capability bit (bit 16)
  is not set, so there is no ABI impact on unsupported hardware.

Suggested-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Signed-off-by: Vishnu Sankar <vishnuocv@gmail.com>
Link: https://patch.msgid.link/20260709021504.465792-1-vishnuocv@gmail.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

0 files changed, 0 insertions, 0 deletions