Note: This function is supported in AIX® 5.1 and earlier only.
Provides the means for transmitting data to the Multiprotocol Quad Port (MPQP) device.
#include <sys/uio.h>
#include <sys/comio.h>
#include <sys/mpqp.h>int mpwrite (devno, uiop, chan, ext)
dev_t devno;
struct uio *uiop;
int chan, ext;| Item | Description |
|---|---|
| devno | Specifies major and minor device numbers. |
| uiop | Points to a uio structure that provides variables to control the data transfer operation. The uio structure is defined in the /usr/include/sys/uio.h file. |
| chan | Specifies the channel number assigned by the mpmpx entry point. |
| ext | Specifies the address of the mp_write_extension parameter block. If the ext parameter is null, no parameter block is specified. |
The mpwrite entry point provides the means for transmitting data to the MPQP device. The kernel calls it when a user-mode process issues a write or writex subroutine. The mpwrite entry point can also be called in response to an fpwrite kernel service.
The MPQP device handler uses a fixed length buffer for transmitting and receiving data. The maximum supported buffer size is 4096 bytes.
The mpwrite entry point functions with a 4-Port Multiprotocol Interface adapter that has been correctly configured for use on a qualified network. Consult adapter specifications for more information on configuring the adapter and network qualifications.
mpwrite Parameter Block
For the mpwrite operation, the ext parameter points to the mp_write_extension structure. This structure is defined in the /usr/include/sys/comio.h file. The mp_write_extension structure contains the following fields:
| Field | Description |
|---|---|
| status | Identifies the status of the port. The possible values for
the returned status field are:
|
| write_id | Contains
a user-supplied correlator. The write_id field
is returned to the caller by the CIO_GET_STAT operation
if the CIO_ACK_TX_DONE flag
is selected in the asynchronous status block. For a kernel user, this field is returned to the caller with the stat_fn function which was provided at open time. |
In addition to the common parameters, the mp_write_extension structure contains a field for selecting Transparent mode for binary synchronous communication (BSC). Any nonzero value for this field causes Transparent mode to be selected. Selecting Transparent mode causes the adapter to insert data link escape (DLE) characters before all appropriate control characters. Text sent in Transparent mode is unaltered. Transparent mode is normally used for sending binary files.
The mpwrite entry point can be called from the process environment only.
The common return codes for the mpwrite entry point are the following:
| Return Code | Description |
|---|---|
| EAGAIN | Indicates that the number of
direct memory accesses (DMAs)
has reached the maximum allowed or that the device handler cannot
get memory for internal control structures. Note: The MPQP device
handler does not currently support the tx_fn function.
If a value of EAGAIN is returned by an mpwrite entry
point, the application is responsible for retrying the write.
|
| ECHRNG | Indicates that the channel number is too high. |
| EINVAL | Indicates one
of the following:
|
| ENOMEM | Indicates that no mbuf structure or clusters are available or the total data length is more than a page. |
| ENXIO | Indicates one
of the following:
|