Removing Dependency between SCSICommand and SCSI / SCSIDevice

• Remove SCSI object from SCSICommand
  • done, we now have a scsi object that has methods to create the suported scsi commands
• Move execution from SCSICommand to SCSI object and there with a explizit call to the SCSIDevice execute method
  • done, the SCSI object get passed a SCSIDevice object the SCSI wrapper methods call the corresponding methods on the device
  • SCSICommand only provides the command related properies and methods
    • done
• With these changes it should be possible to write code even without a SCSI instance created. In the end the SCSI class is just a nice little helper that takes care of the following steps
  • create a SCSIDevice
  • create a SCSICommand
  • pass the SCSICommand to the SCSIDevice.execute method
  • call the marshall/unmarshall methods of the SCSICommand

Adding a ContextManager to SCSIDevice

• This is just a small addition to the SCSIDevice class but it enables the use of the with keyword. It also provides a teardown mechanism for closing the filedescriptor create in the init method. In the actual code we never close the file descriptor properly
• info
  • In the branch refactor_device I added context manager logic
  • There is also a refactoring for SCSIDevice, I refactored the iscsi code into a seperate module and let the SCSI class figure out if we have a iscsi device or a parallel scsi device. The device classes have context manger logic too so it could be used outside the SCSI class still.

Making unmarshall_cdb, marshall_cdb and build_cdb a classmethod of SCSICommand

• After a closer look we see that there is a DRY problem so we should refactor the methods as Baseclass methods
• One solution is to hold a _cdb_bits dict in SCSICommand and override it in the subclasses.
• For build_cdb method we can pass kwargs and build a cdb dict to pass to the marshall_cdb method