Operation
=========

Software
--------

.. note:: Make sure you have installed the control software as described in
  :ref:`Software Commissioning<software-commissioning>`.

Using multiple USB-SD-Muxes on a single host is considered a common use case.
Thus, it is a good practice to access a USB-SD-Mux via the
``/dev/usb-sd-mux/id*`` symlinks created by the provided udev-rule.
The following examples are based on a USB-SD-Mux with the ID 000000000101.

If you have set up the ``udev`` rule to grant access to the USB-SD-Mux control
interface to your current user, you should be able to use it as shown below.
Otherwise you may need to use the ``sudo`` command.

* To multiplex the Micro-SD-Card to the :term:`DUT`

  .. code-block:: bash

    $ usbsdmux /dev/usb-sd-mux/id-000000000101 DUT

.. important::

  The *card insertion detection* signal on the DUT's SD card controller is not
  toggled, when you switch into DUT-mode on the USB-SD-Mux.
  Therefore, you either need to signal this to the DUT externally or simply
  power-cycle the DUT.

* To multiplex the Micro-SD-Card to the host:

  .. code-block:: bash

    $ usbsdmux /dev/usb-sd-mux/id-000000000101 host

* To disconnect the micro SD card from :term:`DUT` and Host:

  .. code-block:: bash

    $ usbsdmux /dev/usb-sd-mux/id-000000000101 off

* To get the current status of the USB-SD-Mux:

  .. code-block:: bash

    $ usbsdmux /dev/usb-sd-mux/id-000000000101 get
    off

.. note::
  The default state of USB-SD-Mux is off.

The block device of an USB-SD-Mux is symbolically linked as

   ``/dev/disk/by-id/usb-LinuxAut_sdmux_HS-SD_MMC_*-0:0``

Tool Integration
----------------

The `labgrid <https://github.com/labgrid-project/labgrid>`_ project has support
for the USB-SD-Mux.
See labgrid's
`documentation <https://labgrid.readthedocs.io/en/latest/configuration.html?highlight=usb-sd-mux#usbsdmuxdevice>`_
for more details.