Moin Mike,

19.11.95 06:53, you wrote a message to Simeon Cran:

 MB> Simeon Cran wrote in a message to All:

 SC>> I'm interested in reading the raw sectors off CD-ROMs. I
 SC>> know that certain CD-ROM readers are capable of this and can
 SC>> be controlled using an ASPI command called something like
 SC>> "READ_RAW".

...

 MB> You can read raw sectors off of a CD-ROM by simply calling 
 MB> DosOpen() against the drive letter with the OPEN_FLAGS_DASD bit 
 MB> asserted.  However, this will fail if CDFS.IFS is loaded, since 
 MB> it claims ownership of the drive letter.

I have no problems to read a data CDROM using the code I posted here the
other day. Any switches different between your and my call to DosOpen?

 MB> If you comment out the load of CDFS.IFS in CONFIG.SYS, then no 
 MB> file system will claim the drive letter created for the CD-ROM 
 MB> drive by OS2CDROM.DMD, and you can do direct access to it.

You can't lock the device if a filesystem driver is loaded. But you don't
need a lock if you're only reading (who wants to write to a CDROM?).

 MB> If you have a file/device handle for the whole drive returned by 
 MB> DosOpen(), then you can either use DosRead() for conventional 
 MB> reads or DosDevIOCtl() in the manner expected by OS2CDROM.DMD for 
 MB> "read long."  That is, "read long" will get you
the full sector 
 MB> with ECC data appended, and you will be responsible for detecting 
 MB> any read errors and applying the ECC code manually.

Perhaps this "read long" will need a lock, DosRead will definitely not.

 MB> The chain of control is that the CD-ROM controller will be 
 MB> claimed by an ADD. OS2CDROM.DMD will issue an 
 MB> IOCC_UNIT_CONTROL/IOCM_ALLOCATE_UNIT command to the ADD at boot 
 MB> time, and this will prevent ASPI or any other device driver from 
 MB> successfully allocating the unit.  In order to prevent this, you 
 MB> must either replace OS2CDROM.DMD -- which is strongly not 
 MB> recommended -- or insert your own FLT into the chain between the 
 MB> ADD and OS2CDROM.DMD.

You may control the allocation by adding switches to you ADD commandline.
All driver I know support a commandline as documented for AHA154X.ADD
(online help).
/AM:(target,lun)	use with ASPI DMD
/SM:(target,lun)	use with SCSI DMD
/DM:(target,lun)	use with DASD DMD

The comments in the source of OS2CDROM.DMD declare a device with /!DM set
won't by allocated. But this flag is never tested. Perhaps the production
code works that way.

 MB> If you only need this kind of access for testing purposes on your 
 MB> own system, then commenting out CDFS.IFS and using OS2CDROM.DMD 
 MB> directly is probably the easiest thing to do.  If you need to 
 MB> make redistributable code, then you will have to write an FLT in 
 MB> order to hide the unit from OS2CDROM.DMD so that you can use it.  
 MB> Hiding a unit can be an involved project.

I don't think he has to do all those things. But I'm willing to test any
code which proves the contrary (how do you spell THIS?).

...

Tschuesz,
	Vitus 

PIN: 10:1000/100.20
Fido: 2:2474/100.20
Internet: vitus{at}vortex.de

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