DeviceExtension not getting allocated by IoCreateDevice()...

NTDEV
1

When I use IoCreateDevice() to create a device object (for filtering
volumes), for some strange reason it’s not allocating my device extension.
Here’s how I’m doing it:

status = IoCreateDevice(pDriverObject,
sizeof(LOWIRQL_FILTER_EXTENION),
NULL,
FILE_DEVICE_DISK,
0,
FALSE,
&pFilterDeviceObject);

LOWIRQL_FILTER_EXTENION is defined as:

typedef struct _LOWIRQL_FILTER_EXTENION {
PDEVICE_OBJECT pThisDeviceObject;
PDEVICE_OBJECT pLowerDeviceObject;
ULONG DiskNumber;
ULONG DiskSignature;
ULONG PartitionNumber;
LONGLONG PartitionOffset;
LONGLONG PartitionLength;
BOOLEAN bDeletePending;
} LOWIRQL_FILTER_EXTENION, *PLOWIRQL_FILTER_EXTENION;

I’m writing a driver for NT4, but I’m testing it on my W2K machines, and
DriverExtension never gets allocated.

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2

On Friday, March 09, 2001 1:09 AM “Nate Bushman” wrote:

When I use IoCreateDevice() to create a device object (for filtering
volumes), for some strange reason it’s not allocating my device
extension.
Here’s how I’m doing it (…)

Hi, Nate.
Your LOWIRQL_FILTER_EXTENION ( you’ve a typing error here:
the word is …_EXTENSION… :wink: ) seems to be allright. The problem
might be that as you’re testing your NT4 driver on a W2K system, you
should provide an NT-like name string on the third parameter to
IoCreateDevice. Try this:

// Use an unicode string
//
UNICODE_STRING NTNameString;

// Create counted string version of our device name
//
RtlInitUnicodeString (&NTNameString, YOUR_DEVICE_NAME_NT);

// Create the device object
//
status = IoCreateDevice(pDriverObject,
sizeof(LOWIRQL_FILTER_EXTENION),
&NTNameString,
FILE_DEVICE_DISK,
0,
FALSE,
&pFilterDeviceObject);

YOUR_DEVICE_NAME_NT should be something like:

#define YOUR_DEVICE_NAME_NT L"\Device\your_driver_name" // NT device
name

Also, you should check if the FILE_DEVICE_DISK value is appropriate
to your device (maybe you have to define your own value here; if that is
the case, this value should be in the range 0x8000 to 0xFFFF - check the
docs).

Hope it helps, :wink:

Miguel Monteiro
xxxxx@criticalsoftware.com
www.criticalsoftware.com

«Humour and love are God’s answers
to Human weaknesses»

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3

>

I’m writing a driver for NT4, but I’m testing it on my W2K machines, and
DriverExtension never gets allocated.

Point of clarification: Your DRIVER extension doesn’t get allocated, or your
DEVICE extension doesn’t get allocated?

There are both Driver and Device extensions, so this isn’t an attempt to be
“cute”…

Peter
OSR

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