Using the SC_DIAGNOSTIC Option

The SC_DIAGNOSTIC option causes the device driver to enter Diagnostic mode for the given device. This option directs the device driver to perform only minimal operations to open a logical path to the device.

No commands should be sent to the device in the open or close routine when the device is in Diagnostic mode. One or more ioctl operations should be provided by the device driver to allow the caller to issue commands to the attached device for diagnostic purposes.

The SC_DIAGNOSTIC option gives the caller an exclusive open to the selected device. This option requires appropriate authority to run. If the caller attempts to execute this system call without the proper authority, the device driver should return a value of -1, with the errno global variable set to a value of EPERM. The SC_DIAGNOSTIC option may be executed only if the device is not already opened for normal operation. If this ioctl operation is attempted when the device is already opened, or if an openx call with the SC_DIAGNOSTIC option is already in progress, a return value of -1 should be passed, with the errno global variable set to a value of EACCES. Once successfully opened with the SC_DIAGNOSTIC flag, the device driver is placed in Diagnostic mode for the selected device.