IOCTL_READ_REGISTERS IOCTL (usbscan.h)
Reads from USB device registers, using the control pipe.
Major code
Input buffer
Pointer to an IO_BLOCK structure.
Input buffer length
Size of the input buffer.
Output buffer
Pointer to a buffer to receive register contents.
Output buffer length
Size of the output buffer. The value must match the contents of the uLength member of the IO_BLOCK structure.
Status block
Irp->IoStatus.Status is set to STATUS_SUCCESS if the request is successful. Otherwise, Status to the appropriate error condition as a NTSTATUS code.
Remarks
DeviceIoControl Parameters
When the DeviceloControl function is called with the IOCTL_READ_REGISTERS I/O control code, the caller must specify the address of an IO_BLOCK structure as the function's lpInBuffer parameter.
Using the IO_BLOCK contents, the kernel-mode driver creates a URB that contains a _URB_CONTROL_VENDOR_OR_CLASS_REQUEST structure.
The following table indicates the values assigned to _URB_CONTROL_VENDOR_OR_CLASS_REQUEST structure members.
| Structure Member | Value Assigned |
|---|---|
| TransferFlags | 1 |
| TransferBufferLength | pIoBlock->uLength |
| TransferBuffer | DeviceIoControl's lpOutBuffer argument. |
| TransferBufferMDL | NULL |
| RequestTypeReservedBits | 0xC0 |
| Request | (pIoBlock->uLength > 1) ? 0x04 : 0x0C |
| Value | (SHORT)pIoBlock->uOffset |
| Index | pIoBlock->uIndex |
For more information, see Accessing Kernel-Mode Drivers for Still Image Devices.
Requirements
| Requirement | Value |
|---|---|
| Header | usbscan.h (include Usbscan.h) |