Plextor PowerRec for users

Plextor PowerRec for users

[Thomas Maguin]

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Please add the following entries to allow :
command opcodes for PoweRec, VariRec (0xED & 0xEB)
and further settings opcodes  0xE9 on Plextor devices
as normal user.

/usr/src/linux/scsi/scsi.h
+#define PLEXTOR_MODE                  0x39
+#define PLEXTOR_PREC_SPEEDS   0x3B
+#define PLEXTOR_MODE2                0x3D

/usr/src/linux/block/scsi/scsi_ioctl.c
+safe_for_read(PLEXTOR_MODE)
+safe_for_read(PLEXTOR_PREC_SPEEDS)
+safe_for_read(PLEXTOR_MODE2)



Thomas Maguin

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Re: Plextor PowerRec for users

[Thomas Maguin]

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Blame on me, a typo in the addresses. Changes should be this:
(patch is on the way)

/usr/src/linux/include/scsi/scsi.h
+#define PLEXTOR_MODE                  0xe9
+#define PLEXTOR_PREC_SPEEDS   0xeB
+#define PLEXTOR_MODE2                0xeD

/usr/src/linux/block/scsi/scsi_ioctl.c
+safe_for_read(PLEXTOR_MODE)
+safe_for_read(PLEXTOR_PREC_SPEEDS)
+safe_for_read(PLEXTOR_MODE2)




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Re: Plextor PowerRec for users

[Matthew Wilcox]

On Sun, Feb 12, 2006 at 05:18:04PM +0100, Thomas Maguin wrote:
> Blame on me, a typo in the addresses. Changes should be this:
> (patch is on the way)
> 
> /usr/src/linux/include/scsi/scsi.h
> +#define PLEXTOR_MODE ?? ?? ?? ?? ?? ?? ?? ?? ??0xe9
> +#define PLEXTOR_PREC_SPEEDS ?? 0xeB
> +#define PLEXTOR_MODE2 ?? ?? ?? ?? ?? ?? ?? ??0xeD
> 
> /usr/src/linux/block/scsi/scsi_ioctl.c
> +safe_for_read(PLEXTOR_MODE)
> +safe_for_read(PLEXTOR_PREC_SPEEDS)
> +safe_for_read(PLEXTOR_MODE2)

The trouble is that these are vendor-specific commands.  So they're safe
*for plextor devices*, but they may well be unsafe for other vendors.
Given the LG CD-ROM snafu [1], I'd expect people to err on the side
of caution.  Sorry.

[1] http://www.dvd-recordable.org/Article911-mode=thread-order0-threshold0.phtml

Re: Plextor PowerRec for users

[Thomas Maguin]

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This patch allows to normal users on Plextor drives:

- Hide CD-R
- SingleSession
- SpeedRead
- PowerRec
- VariRec
- GigaRec

Can be tested with new qpxtool (testing version available here):
http://de.geocities.com/linux_piewie/download/qpxtool-testing.tgz


--- linux/include/scsi/old-scsi.h       2006-02-12 16:15:40.000000000 +0100
+++ linux/include/scsi/scsi.h   2006-02-12 17:23:20.000000000 +0100
@@ -108,7 +108,11 @@
 #define SEARCH_LOW_12         0xb2
 #define READ_ELEMENT_STATUS   0xb8
 #define SEND_VOLUME_TAG       0xb6
+#define PLEXTOR_MODE          0xe9
 #define WRITE_LONG_2          0xea
+#define PLEXTOR_PREC_SPEEDS   0xeb
+#define PLEXTOR_MODE2         0xed
+
 #define READ_16               0x88
 #define WRITE_16              0x8a
 #define VERIFY_16            0x8f
--- linux/drivers/block/old-scsi_ioctl.c        2006-02-12 16:23:37.000000000 
+0100
+++ linux/drivers/block/scsi_ioctl.c    2006-02-12 16:25:31.000000000 +0100
@@ -159,7 +159,10 @@
                safe_for_read(GPCMD_GET_PERFORMANCE),
                safe_for_read(GPCMD_SEEK),
                safe_for_read(GPCMD_STOP_PLAY_SCAN),
-
+               safe_for_read(PLEXTOR_MODE),
+               safe_for_read(PLEXTOR_PREC_SPEEDS),
+               safe_for_read(PLEXTOR_MODE2),
+               
                /* Basic writing commands */
                safe_for_write(WRITE_6),
                safe_for_write(WRITE_10),

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Re: Plextor PowerRec for users

[Matthew Wilcox]

On Sun, Feb 12, 2006 at 06:35:24PM +0100, Thomas Maguin wrote:
> On Sunday 12 February 2006 17:53, you wrote:
> > The trouble is that these are vendor-specific commands.  So they're safe
> > *for plextor devices*, but they may well be unsafe for other vendors.
> >
> These are just read commands. A correct firmware should just reject the 
> commands. 

I don't think you understand the point.  A non-Plextor device could have
a HALT AND CATCH FIRE command on that opcode.  That definitely wouldn't
be safe.  If 'just a read command' were enough, we wouldn't need to
have filtering for read commands at all.

> Plextor users have been waiting a long time for the features in linux, so 
> please think about a solution which is a solution for all users.

The only solutions I can think of are big and ugly if they're in
the kernel.  Why not write a set-uid helper that checks the device
manufacturer and device type, then issues the appropriate command?
That would work on 2.4 as well as 2.6.

Re: Plextor PowerRec for users

[Matthias Andree]

Matthew Wilcox <matthew@wil.cx> writes:

> On Sun, Feb 12, 2006 at 05:18:04PM +0100, Thomas Maguin wrote:
>> Blame on me, a typo in the addresses. Changes should be this:
>> (patch is on the way)
>> 
>> /usr/src/linux/include/scsi/scsi.h
>> +#define PLEXTOR_MODE ?? ?? ?? ?? ?? ?? ?? ?? ??0xe9
>> +#define PLEXTOR_PREC_SPEEDS ?? 0xeB
>> +#define PLEXTOR_MODE2 ?? ?? ?? ?? ?? ?? ?? ??0xeD
>> 
>> /usr/src/linux/block/scsi/scsi_ioctl.c
>> +safe_for_read(PLEXTOR_MODE)
>> +safe_for_read(PLEXTOR_PREC_SPEEDS)
>> +safe_for_read(PLEXTOR_MODE2)
>
> The trouble is that these are vendor-specific commands.  So they're safe
> *for plextor devices*, but they may well be unsafe for other vendors.
> Given the LG CD-ROM snafu [1], I'd expect people to err on the side
> of caution.  Sorry.

The LG disaster is unrelated, they overloaded a *standard* command for
their own purposes. Outright stupid, but that's LG's problem, not
Linux's.

This is about vendor-specified opcodes being whitelisted. I, too,
consider this dangerous, unless someone desires to implement two tables
in the kernel:

Table 1 maps drive/model/firmware pairs to a command set table (table 2)
-- this is for compression, as many drive/model/firmware patterns can
share the same command whitelist

Table 2 implements the actual whitelists.

And if someone is going this way, perhaps the kernel should only have
the mechanism and receive the tables at boot-time from a user space
process (hotplug or whatever) so it doesn't need to keep a gazillion of
tables in core for drives the user will never have.

-- 
Matthias Andree