* on error.
*
* When 'op' == SCAN_OP_OPEN_DEVICE the function opens the supported USB
* device with index 'open_device_index' and returns the correspondent
* am7xxx_device in the 'dev' parameter; the function returns the value from
* on error.
*
* When 'op' == SCAN_OP_OPEN_DEVICE the function opens the supported USB
* device with index 'open_device_index' and returns the correspondent
* am7xxx_device in the 'dev' parameter; the function returns the value from