Persistent Write Protection

keiji_katata at keiji_katata at
Wed Oct 13 04:31:14 PDT 1999

* From the T10 Reflector (t10 at, posted by:
* keiji_katata at

  Hello all,

  I'm  Keiji  Katata  of  PIONEER.  Now Mt.Fuji4 group are discussing about
  Persistent  Write Protection as I reported. DVD Forum defines Media Write
  Protection,  "Write Inhibit Flag" for DVD-RAM, and "Write Protection Disc
  status"  for  DVD-RW.  They  are  same  functionality. The information is
  stored  on the medium surface. Currently, while Media Write Protection is
  set,  any  writing  on  sectors  is  not  allowed  except the Media Write
  Protection Status change.

  The  similar  functionality  is  defined in SCSI-3 Stream Device Commands
  (SSC).  They  use  Mode  Parameter  (MODE  SENSE/ MODE SELECT Command) to
  control PWP.
  MMC2   and  Mt.Fuji  members  discussed  about  characteristics  of  Mode
  Parameter  Data  and have reached to a conclusion. The conclusion is that
  Mode  Parameter  Data shall be stored in Device. When media is changed on
  Removal  Media device, UNIT ATTENTION of Mode Parameter Changed shall not
  be reported. This means that the current value and changeable value shall
  be  stored  in  Device  and  shall  not be changed though medium has been
  changed.  But  MMC  device  is  very  complicated.  So  to  help the host
  programmers, the default value can be changed to the vender's recommended
  value of the installed media.
  Because  of this conclusion, in October meeting, we decided that we can't
  use  Mode  Parameter  to  control  PWP.  I don't know how SSC defines the
  device behavior when PWP is changed via media change.

  Currently,  we  have  a pair of commands that can send and read the meida
  specific  data named "READ DVD STRUCTURE Command" and "SEND DVD STRUCTURE
  Command".  They  are  very  specific  commands for DVD. But we don't have
  other proper commands for this purpose. The meaning of "SEND" in its name
  is  the data sent from host may not be written at the command completion.
  It  will  be  applied at timing defined by the media specification and/or
  the Format code definition appropriately.
  I  feel  that  the command name should be changed, for example "READ DISC
  STRUCTURE". And the Format code for Write Protection Setting of installed
  media  can  be  higher number, for example 0C0h. In this case, the device
  which  supports PWP, shall support Format Code 0C0h and 0FFh. Format Code
  0FFh  reports  what  format  codes  are supported via "READ DVD STRUCTURE

  Currently, we have 3 kinds of Write Protection Setting for Device Type 5.
  1st is SWP in Mode Parameter " Time-out & Protect Page Format : 1Dh". 2nd
  is  Write  Protect  Switch  of Medium Cartridge. 3rd is PWP. All settings
  shall  be reported via this Format Code. PWP shall be changeable via this
  Format Code.

  Anyway, we don't have the intention to limit this discussion/feature into
  DVD media. We welcome to any reply for this message.

  Best Regards.

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