Interference of cdrskin and cdrecord operating on different drives

[scdbackup@gmx.net]

Hi Joerg,

i found that my program cdrskin keeps your program cdrecord
from starting in a peculiar situation when both are used
simultaneously on differend drives.

Situation:
cdrskin is in the process of burning on dev=0,0,0
cdrecord shall perform -atip on dev=0,1,0 

With cdrecord of cdrtools-2.01.01a23-pre.tar.bz2
(which reports "2.01.01a22"):

  $ cdrecord dev=0,1,0 -v -atip
  Cdrecord-ProDVD-Clone 2.01.01a22 (i686-pc-linux-gnu) Copyright (C) 1995-2006 Jörg Schilling
  TOC Type: 1 = CD-ROM
  scsidev: '0,1,0'
  scsibus: 0 target: 1 lun: 0
  cdrecord: Device or resource busy. Cannot open '/dev/sg0'. Cannot open SCSI driver.
  cdrecord: For possible targets try 'cdrecord -scanbus'.
  cdrecord: For possible transport specifiers try 'cdrecord dev=help'.
  $

Note that /dev/sg0 corresponds to the drive which
cdrecord addresses as dev=0,0,0. I.e. the complaint
is not about the drive which cdrecord shall operate on.

The phenomenon is not new in cdrecord. 
It affects versions at least as old as 
  Cdrecord 2.0 (i686-pc-linux-gnu) Copyright (C) 1995-2002 Jörg Schilling
with the same failure messages.


The same -atip gesture works well if the corresponding
device file address /dev/sg1 is used

  $ cdrecord dev=/dev/sg1 -v -atip
  Cdrecord-ProDVD-Clone 2.01.01a22 (i686-pc-linux-gnu) Copyright (C) 1995-2006 Jörg Schilling
  ...
  Warning: Open by 'devname' is unintentional and not supported.
  ...
  Current: CD-RW
  ...
      Capacity  Blklen/Sparesz.  Type
         18450             2048  Formatted Media
 

I do not see much chance to influence the problem from
the side of cdrskin. At that moment /dev/sg0 is open
 O_EXCL | O_NONBLOCK | O_RDWR
which is the minimum impact cdrskin can live with.

/dev/sg1 reports 0 "opens" in /proc/scsi/sg/devices 
(field 6 according to /proc/scsi/sg/device_hdr ).

As soon as /dev/sg0 is free again, dev=0,1,0 works
fine with cdrecord for -atip, blanking and burning.


Have a nice day :)

Thomas