2.11. WD_Transfer()


	Chapter 2. WD_xxx PCI/PCMCIA/ISA Functions

Purpose

Executes a single read/write instruction to an I/O port or to a memory address.

Prototype

DWORD WD_Transfer(
    HANDLE hWD,
    WD_TRANSFER *pTrans);

Parameters

Name	Type	Input/Output
hWD	HANDLE	Input
pTrans	WD_TRANSFER*
• cmdTrans	DWORD	Input
• dwPort	KPTR	Input
• dwBytes	DWORD	Input
• fAutoinc	DWORD	Input
• dwOptions	DWORD	Input
• Data	union
* Byte	BYTE	Input/Output
* Word	WORD	Input/Output
* Dword	UINT32	Input/Output
* Qword	UINT64	Input/Output
* pBuffer	PVOID	Input/Output

Description

Name	Description
hWD	Handle to WinDriver's kernel-mode driver as received from `WD_Open`() [5.2]
pTrans	Pointer to a transfer information structure:
• cmdTrans	A value indicating the type of transfer to perform — see definition of the `WD_TRANSFER_CMD` enumeration in windrvr.h. In calls to `WD_Transfer`() the transfer command should be a read/write transfer command that conforms to the following format: `<dir><p>_[S]<size>` Explanation: `<dir>`: `R` for read, `W` for write `<p>`: `P` for I/O, `M` for memory `<S>`: signifies a string (block) transfer, as opposed to a single transfer `<size>`: BYTE, WORD, DWORD or QWORD .
• dwPort	The memory or I/O address to access. For a memory transfer, use the kernel-mapping of the base address received from `WD_CardRegister`() [2.8] in `pCardReg->Card.Item[i]I.Mem.dwTransAddr` (where 'i' is the index of the relevant memory item) + the desired offset from the beginning of the address range. For an I/O transfer, use the base address received from `WD_CardRegister`() [2.8] in `pCardReg->Card.Item[i]I.IO.dwAddr` (where 'i' is the index of the relevant I/O item) + the desired offset from the beginning of the address range.
• dwBytes	Used in string transfers — number of bytes to transfer
• fAutoinc	Used for string transfers. If `TRUE`, I/O or memory address should be incremented for transfer. If `FALSE`, all data is transferred to the same port/address.
• dwOptions	Must be set to 0
• Data	The transfer data — input for read transfers, output for write transfers:
* Byte	Used for 8-bit transfers
* Word	Used for 16-bit transfers
* Dword	Used for 32-bit transfers
* Qword	Used for 64-bit transfers
* pBuffer	Used for string (block) transfers

Return Value

Returns WD_STATUS_SUCCESS (0) on success, or an appropriate error code otherwise [A].

Remarks

64-bit data transfers (QWORD) are available only for memory string transfers.
Such transfers require 64-bit enabled PCI device, a 64-bit PCI bus, and an x86 CPU running under any of the operating systems supported by WinDriver. (Note: 64-bit data transfers performed with WD_Transfer() do not require 64-bit operating system/CPU).
When using WD_Transfer(), it is important to align the base address according to the size of the data type, especially when issuing string transfer commands. Otherwise, the transfers are split into smaller portions. The easiest way to align data is to use basic types when defining a buffer, i.e.:
```
BYTE buf[len];    /* For BYTE transfers - not aligned */
WORD buf[len];    /* For WORD transfers - aligned on 2-byte boundary */
UINT32 buf[len];  /* For DWORD transfers - aligned on 4-byte boundary */
UINT64 buf[len];  /* For QWORD transfers - aligned on 8-byte boundary */
```

Example

WD_TRANSFER Trans;
BYTE read_data;

BZERO(Trans);
Trans.cmdTrans = RP_BYTE; /* Read Port BYTE */
Trans.dwPort = 0x210;
WD_Transfer(hWD, &Trans);
read_data = Trans.Data.Byte;


2.10. WD_CardUnregister()		2.12. WD_MultiTransfer()