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NC:parallel.PPARALLEL_TRY_SELECT_ROUTINE

PPARALLEL_TRY_SELECT_ROUTINE (parallel.h)

The PPARALLEL_TRY_SELECT_ROUTINE-typed callback routine selects an IEEE 1284.3 daisy chain device or an IEEE 1284 end-of-chain device that is attached to a parallel port. The system-supplied function driver for parallel ports supplies this routine.

parports\pparallel_try_select_routine.htm

parports

02/15/2018

PPARALLEL_TRY_SELECT_ROUTINE callback

(*PPARALLEL_TRY_SELECT_ROUTINE), (*PPARALLEL_TRY_SELECT_ROUTINE) callback function [Parallel Ports], cisspd_ec7d6b68-7fbd-493e-9787-3e2f78327bdd.xml, parallel/(*PPARALLEL_TRY_SELECT_ROUTINE), parports.pparallel_try_select_routine

parallel.h

Parallel.h

Desktop

<=DISPATCH_LEVEL

Windows

RILGBATOKEN, *LPRILGBATOKEN

PPARALLEL_TRY_SELECT_ROUTINE

parallel/PPARALLEL_TRY_SELECT_ROUTINE

APIRef

kbSyntax

UserDefined

parallel.h

PPARALLEL_TRY_SELECT_ROUTINE

PPARALLEL_TRY_SELECT_ROUTINE callback

-description

The PPARALLEL_TRY_SELECT_ROUTINE-typed callback routine selects an IEEE 1284.3 daisy chain device or an IEEE 1284 end-of-chain device that is attached to a parallel port. The system-supplied function driver for parallel ports supplies this routine.

-parameters

-param TrySelectContext [in]

Pointer to the device extension of a parallel port's functional device object (FDO).

-param TrySelectCommand [in]

Pointer to a PARALLEL_1284_COMMAND structure. The caller specifies the following members:

ID

Specifies the 1284.3 device ID.

CommandFlags

Specifies a bitwise OR of zero or more of the following flags:

Value	Description
PAR_END_OF_CHAIN_DEVICE	Specifies an end-of-chain device.
PAR_HAVE_PORT_KEEP_PORT	Specifies that the caller has the port allocated and to keep the port allocated.

-returns

Return code	Description
STATUS_SUCCESS	The device was selected.
STATUS_INVALID_PARAMETER	The device ID is not valid.
STATUS_PENDING	The caller did not specify PAR_HAVE_PORT_KEEP_PORT, and the parallel port is already allocated.
STATUS_UNSUCCESSFUL	The caller has allocated the parallel port, but the system-supplied function driver for parallel ports could not select the specified parallel device.

-prototype

typedef NTSTATUS (*PPARALLEL_TRY_SELECT_ROUTINE)(
  _In_ PVOID TrySelectContext,
  _In_ PVOID TrySelectCommand
);

-remarks

To obtain a pointer to the system-supplied PPARALLEL_TRY_SELECT_ROUTINE callback, a kernel-mode driver uses an IOCTL_INTERNAL_GET_PARALLEL_PNP_INFO request, which returns a PARALLEL_PNP_INFORMATION structure. The TrySelectDevice member of the PARALLEL_PNP_INFORMATION structure is a pointer to this callback.

A kernel-mode driver can use an IOCTL_INTERNAL_SELECT_DEVICE request or the PPARALLEL_TRY_SELECT_ROUTINE callback to select a parallel device on a parallel port. The parallel port function driver queues a select request if the parallel port is already allocated. However, the PPARALLEL_TRY_SELECT_ROUTINE callback does not queue a select request, and the routine returns immediately if the port cannot be allocated.

Note If a client uses only the PPARALLEL_TRY_SELECT_ROUTINE callback to attempt to select a parallel device, and other clients are contending for the parallel port, the system-supplied function driver for parallel ports might never allocate the port to the client. To ensure success, a client must use an IOCTL_INTERNAL_SELECT_DEVICE request. (The parallel port function driver queues, and subsequently processes, port allocate requests and device select requests in the order in which select device requests are received.)