Everhart,Glenn
From: Jeffrey S. Goldner [goldner@pathlight.com]
Sent: Wednesday, April 01, 1998 9:16 AM
To: 'Sampath Kawiratne'; ntdev@atria.com
Subject: RE: [ntdev] Problems on SCSI optical disk
In order to use SCSI Passthrough (SPTI), you need to obtain a handle to the
actual physical device if a device is "claimed" by a class driver (disk,
scsitape, cdrom, etc.) This is the case for your device, so... you must
scan for yourself to find the device you want. You can do a
IOCTL_SCSI_GET_INQUIRY_DATA on a handle to a bus (\\.\Scsi%d) to obtain
(some of) the inquiry data for all devices on the bus, but you won't be
able to talk to the device itself.
Your options are:
1) using SPTI, open each PhysicalDrive, then create a SCSI Inquiry CDB,
check the appropriate fields (which for you would probably involve device
type, and maybe manufacturer and model). If it's your device, you can use
Read and Write CDBs pretty easily (make sure your buffers are aligned
properly - you can tell what the alignment requirement is by asking the bus
driver using IOCTL_SCSI_GET_CAPABILITIES on a handle to Scsi%d). The
problem with SPTI is low performance, single threaded, etc. That may not
bother you.
2) You could use ASPI, but it isn't a standard part of NT. You need to
obtain the aspi32 driver (you can try the Adaptec web site), but the latest
version checks for adaptec controllers or previous ASPI installation. You
also need to obtain the header and import library (or use LoadLibrary) and
arrange to distribute it with your application. The advantages are: it's
transportable, the same code will run on Win9X, which does have ASPI as a
standard component, and other systems as well; it has much higher
performance; it's a little easier to build the CDBs and code in general. It
doesn't support timeouts however. Also, if you know the bus, target, lun
you can get right to your device. In any case, you don't need to mess with
the physicaldrive scanning, just scan by target.
SPTI is documented in the DDK (and src\storage\class\spti has sample code).
SPTI will support any arbitrary CDB that the device supports, but it
doesn't handle any IOCTL codes. It only enters the SCSI miniports using
SRB_FUNCTION_EXECUTE_SCSI. There is no support for symbolic links, which I
don't see as appropriate here anyway.
Your best bet is to write a DLL using either SPTI or ASPI and expose
routines that are important to you. User programs then call into the DLL. A
device driver would have to be a class driver and you'd have to attach to
the device first before disk.sys gets there.
Jeff Goldner
Pathlight Technology
-----Original Message-----
From: Sampath Kawiratne [SMTP:dssk@sri.lanka.net]
Sent: Monday, March 30, 1998 9:15 AM
To: ntdev@atria.com
Subject: [ntdev] Problems on SCSI optical disk
Hello everybody,
I am new to the NT device driver field and hope that you could be good
enough to help me out with the following problems.
My requirement is to provide sector level read/write access for user level
programs to a SCSI optical disk (OD). Initially I thought that I would have
to write a device driver for this but later onwards figured out that, it
was possible to obtain a handle to the OD using something like
hDeviceHandle = CreateFile("\\\\.\\PhysicalDrive1",
GENERIC_READ|GENERIC_WRITE,
FILE_SHARE_READ|FILE_SHARE_W
RITE,
NULL,
OPEN_EXISTING,
FILE_FLAG_NO_BUFFERING,
NULL);
The main problem I have with this approach is, programmatically identifying
which physical drive the actual OD is attached to (e.g. PhysicalDrive0,
PhysicalDrive1...Etc). Initially I tried using the
IOCTL_DISK_GET_DRIVE_GEOMETRY IoCtrl but it can only tell that the device
supports removable media other than floppy disk. Next I tried
IOCTL_GET_CAPABILITIES call but this can only identify the device type as
fixed.
Could you please answer my following questions.
1. Are there any disadvantage/limitations of using DeviceIoControl rather
than developing my own device driver?
2. What is the best way to identify the OD from user level programs?
3. What is SCSI passthrough and from where can I get more information about
it. Could SCSI passthrough be used to access all the routines supported by
a driver (other than those supported by IOCTRL codes)? For example can I
use Scsi passthrough to create a symbolic link.
Thanks & Regards,
Sampath.
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