Re: Lock drive

[Joerg Schilling <Joerg Schilling fokus fraunhofer de>]

Thomas Schmitt <scdbackup gmx net> wrote:

> Hi,
>
> Lelouch the Kid:
> > > If you guys could explain to me how the lock drive works and how can I do
> > > that, I would be eternally grateful.
>
> Joerg Schilling:
> > Just call 
> >         cdrecord -lock
>
> This is not enough didactical effort to gain eternal gratitude.

Well, this iw not correct, as cdrecord offers the -V option

> At the lowest level which is in reach for us, the tray locking is
> done by SCSI command 0x1E PREVENT ALLOW MEDIUM REMOVAL. It is
> documented in volume SPC of the SCSI specs. E.g. SPC-3.
> Lock:    1E 00 00 00 01 00
> Unlock:  1E 00 00 00 00 00
>
> Afaik, this has no effect on laptop drives with no tray motor.

You are wrong.

> On e.g. Linux we transport this command to the drive by ioctl(SG_IO).
> See struct sg_io_hdr in /usr/include/scsi/sg.h.

Why using something non-portable when there is a highly portable libscg that is 
part of cdrtools?

Jörg

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