Write Protection Model
Takaharu Ai
aiai at dsd.mei.co.jp
Tue Dec 21 18:00:45 PST 1999
* From the T10 Reflector (t10 at t10.org), posted by:
* Takaharu Ai <aiai at dsd.mei.co.jp>
*
Hi Katata-san and folks
I am sorry but the last message I sent was not completed. Please ignore it.
This is the correct message from me.
---Start of the original message ------------------------------------
>From: keiji_katata at post.pioneer.co.jp
>Date: Mon, 20 Dec 1999 14:02:08 +0900
>To: aiai at dsd.mei.co.jp
>Cc: mtfuji2 at dt.wdc.com, mmc at dt.wdc.com, t10 at t10.org
>Subject: Re: Write Protection Model
>
>
> Takaharu Ai, <aiai at dsd.mei.co.jp> wrote:-------------------
>
> Dear Kohda-san,
>
> I ams sorry for late responce but we have some comments regarding
> Pioneer's write protection proposals.
>
> Here are Matsushita's comments and counter proposal regarding Write
> Protection Model.
>
> 1) MECHANISM STATUS command
> - In the Mt.Fuji3 specification, no information regarding a type and
> other property of a medium in each slot is in the Slot Table Response
> format. The purpose of this command is to obtain an information of the
> current situation of a "Slot" not a disc. It means that a property of a
> medium shall be maintained by Host not Logical Unit. So we think the
> extension in your proposal is not needed.
>
> 2) Event Reporting
> - According to you proposal, Logical Unit shall generate Class 1 Event
> when the Write Protection status is changed. But my understanding is that
> the Class 1 Event is generated when the Logical Unit's behavior is
> changed by for example changing its microcode. But the Write Protection
> status is based on the disc not the Logical Unit. Even if the PWP bit is
> changed to one by a command, no Feature is added and no Microcode is
> changed. So we think the Class 1 is not appropriate.
> - Our counter proposal is to generate Class 4 Event instead of Class 1
> Event. Because the changing of PWP is very similar to change medium.
>
> 3) Write Protection Feature
> - The meaning that Feature which is returned by GET CONFIGURATION command
> is that the function which is specified by the Feature is "supported" by
> the Logical Unit regardless of the function is currently executable or
> not. In your proposals, the Feature indicates that the Logical Unit can
> report the write protection status.
> It means if the READ DVD STRUCTURE command with Format code C0h is
> "supported" by a Logical Unit, this Feature shall be reported regardless
> of the command is executable or not.
> - The Current bit shall be set to one when the functionality indicated by
> the Feature is currently executable. According to Pioneer's proposal, the
> Write Protection Feature indicates to support the functionality to report
> the Write Protection status of the medium though READ DVD STRUCTURE
> command with Format code C0h. When a media is inserted, this command is
> executable I think. So the Current bit is set to one when a writable
> medium is mounted.
> - This is to clarify, but does the SWPW bit is set to one if the Logical
> Unit "support" the READ DVD STRUCTURE command with Format code C0h even
> when the mounted medium is write protected by the write protect tab on
> the cartridge?
>
> Best Regards,
>
> Takaharu Ai
> SDBD/AVC/MEI
> Osaka, Japan
> ------------------------------
> About "1) MECHANISM STATUS command", so I remove PWP from the Slot Table
> Response format. The CWP in the Slot Table Response format provides
> "Partial Medium Load for MAM Access" like functionality. Some device can
> read CWP status without loading the cartridge into its play position.
I understand the intention of your proposal. I agree with you.
>
> About "2) Event Reporting", I disagree completely. 1st reason is this is
> class 1 event, not class 4 event. 2nd reason is reporting class 4 event
> may confuse the system. Usually the system which supports writing on the
> media by particular file system shall supports reading the media and the
> used file system. There is no advantage useing class 4.
My understanding is that the Write Protection Status change Event is same as
Formatting.
When an unformatted DVD-RAM medium is mounted in the Logical Unit, the Random
Readable and Random Writable Features with Current bit set to zero are returned. If
the medium is formatted, these Features become Current.
This is the same situation as the Write Protection status change. When a Persistent
Write Protected 4.7GB DVD-RAM medium is mounted in the Logical Unit, the Random
Writable and Formattable Features with Current bit set to zero are returned. If the
medium is write permitted through SEND DVD STRUCTURE command, these Features become
Current.
According to the Mt.Fuji3 document, the Class 1 event is applied to inform that
medium has been formatted. But the Class 1 Event itself is not mandatory for
Formattable Feature. I think some of devices does not implement Class 1 Event and
it is still Mt.Fuji3 Compliant device. Changing of Write Protection status should
be the same as Formatting. Generation of Class 1 Event shall not be mandatory.
So I would like to change my proposal to as follows,
8.4 Event Reporting
When Write Protection status of mounted medium and/or Logical Unit is changed
(e.g. all of Write protections are cleared or one of them is set to active), any
Features that allows erasing/formatting/writing on media are changed, the Logical
Unit may generate Class 1 Events.
> About "3) Write Protection Feature", I may not understand the all meaning
> of this comment. But it may be as follows. Reading write protection
> status and Setting write protection status shall be separated same as
> "Random Readable Feature" & "Random Writeable Feature". But it is
> redundant, it is too much for such a write protection issue, I think. If
> no media status or ROM media in the device is defined as write protected
> status because any write shall be failed, reading write protection status
> can be "Persistent". But in December meeting, we decided that without
> media, Read DVD Structure command with format code C0h shall be
> terminated with Check Condition. Then it is not Persistent.
> However, there is no need to use current bit to show "you can see the
> write protection status now". Because if media is installed, you can see
> the write protection status that is defined by the media specification
> always.
I am sorry for my unclear explanation.
I meant your proposal had an inconsistency about the definition of the Feature and
the Current bit.
<<from the definition of the Feature>>
According to your proposal, the Write Protect Feature indicates a Logical Unit has
an ability to report the write protect status by READ DVD STRUCTURE command with
Format code C0h. This means that the Current bit of this feature shall be set to
one when the ability to report the write protect status is active, i.e. when the
READ DVD STRUCTURE command with Format code C0h can be executed normally, this
Feature shall be Current.
<<from the definition of the Current bit>>
According to your proposal, the definition of the Current bit is that the bit shall
be set to zero if the Logical Unit can not set/release the PWP status on the
mounted media surface. This means the Write Protect Feature shall indicate a
Logical Unit has an ability to change PWP status of the media.
The meaning of my original proposal was that the definition of the Current bit
should be changed to as follows,
Current bit shall be defined as in Table 109-Feature Descriptor generic format on
page 228. This bit shall be set to one if the Logical Unit can report write
protect status on the mounted medium surface through READ DVD STRUCTURE command
with Format code C0h.
But Tokumitsu-san sent another comment about this issue as follows.
According to his comment, he pointed out the same inconsistency with mine. But the
solution is different. He said the definition of the Feature should be change to
indicate a Logical Unit is capable of changing the PWP status.
The weak point of my proposal is that Host can not know the function of changing
PWP status is currently active or not.
According to Tokumitsu-san's proposal, Host can know it. The important point of
this Feature is to report the changing of PWP status is supported or not and it is
currently executable or not. His proposal can do that. So I agree with
Tokumitsu-san.
---Start of the original message ------------------------------------
>From: tokumitsu at cm.tookai.hitachi.co.jp
>Date: Tue, 21 Dec 99 22:30:06 +0900
>To: <aiai at dsd.mei.co.jp>, <keiji_katata at post.pioneer.co.jp>
>Cc: <mtfuji2 at dt.wdc.com>, <mmc at dt.wdc.com>, <t10 at t10.org>
>Subject: Re[2]: Write Protection Model
>
>* From the T10 Reflector (t10 at t10.org), posted by:
>* tokumitsu at cm.tookai.hitachi.co.jp
>*
>
> Dear Katata-san,
>
> I am Kenji Tokumitsu of Hitachi.
> I cannot understand the commnet from Ai-san of MEI and your response about
> the Write Protect Feature.
>
> So, I am sending my comment about the Write Protect Feature.
>
> The definition of the Write Protect Feature proposed by Pioneer looks
> strange.
>
> The definition is "This Feature shall indicates that the Logical Unit can
> report the write protect status.".
> According to this definition, I think that the Current bit shall be set to
> one when the Logical Unit can report write protect status, even if the
> Logical Unit cannot change the PWP status for mounted medium.
> But, there is a description that "the Current bit shall bet to zero if the
> Logical Unit can not set/release the PWP status on the mounted media
> surface.", in the proposal.
>
> In case of DVD-RAM drive, the drive will support both 2.6GB DVD-RAM media
> and 4.7GB DVD-RAM media. The Write Inhibit Flag is not exist on 2.6GB DVD-
> RAM media. However, the drive can report write protect status for 2.6GB
> DVD-RAM media. So, the Current bit shall be set to one for 2.6GB DVD-RAM
> media. But, according to the proposal of Pioneer, the Current bit shall
> be set to zero for 2.6GB DVD-RAM media, because the PWP status of 2.6GB
> DVD-RAM media is not changeable.
> It looks strange.
>
> So, I think that the definition of the Write Protect Feature should be
> changed as follows.
>
> ----
> This Feature shall indicate that the Logical Unit is capable of changing
> the PWP status. This Feature shall be applied to Random writable or
> Overwritable Logical Unit only.
>
> The READ DVD STRUCTURE Command with Format code C0h and FFh and the SEND
> DVD STRUCTURE Command with Format Code C0h shall be supported.
> ----
>
> And the SPWP bit in Table 118 and the following descriptions are not
> necessary.
>
> ----
> The Supports PWP(SPWP) bit indicates that the Logical Unit supports set/
> release PWP status. If SPWP bit is set to one, the SEND DVD STRUCTURE
> Command with Format=C0h shall be supported.
> ----
>
> Best Regards,
>
> Kenji Tokumitsu
Best Regards,
Takaharu Ai
SDBD/AVC/MEI
Osaka, Japan
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