Loopback Device Driver. More...

Functions
devcall	loopbackClose (device *devptr)

devcall	loopbackControl (device *devptr, int func, long arg1, long arg2)

devcall	loopbackGetc (device *devptr)

devcall	loopbackInit (device *devptr)

devcall	loopbackOpen (device *devptr)

devcall	loopbackPutc (device *devptr, char ch)

devcall	loopbackRead (device devptr, void buf, uint len)

devcall	loopbackWrite (device devptr, const void buf, uint len)

Detailed Description

Loopback Device Driver.

This module implements a loopback device. Data written to a loopback device is placed into an internal buffer and then provided to later reads from the device.

Function Documentation

devcall loopbackClose ( device * devptr )

Close a loopback device.

Parameters

devptr loopback device table entry

Returns: OK if loopback is closed properly, otherwise SYSERR

devcall loopbackControl	(	device *	devptr,
		int	func,
		long	arg1,
		long	arg2
	)

Control function for loopback devices.

Parameters

devptr	device table entry
func	control function to execute
arg1	first argument for the control function
arg2	second argument for the control function

Returns: the result of the control function

devcall loopbackGetc ( device * devptr )

Get a character from the loopback buffer, possibly blocking.

Parameters

devptr Pointer to the loopback device.

Returns: The resulting ch as an unsigned char cast to an int on success; EOF if there is no data available and the device is in nonblocking mode.

devcall loopbackInit ( device * devptr )

Initialize loopback device

Parameters

devptr

Returns: OK on open

devcall loopbackOpen ( device * devptr )

Open a loopback device.

Parameters

devptr loopback device table entry

Returns: OK if loopback is opened properly, otherwise SYSERR

devcall loopbackPutc	(	device *	devptr,
		char	ch
	)

Put a character onto the loopback buffer

Parameters

devptr	Loopback device
ch	character to output

Returns: ch as an unsigned char cast to an int on success; SYSERR if there is no room in the buffer.

devcall loopbackRead	(	device *	devptr,
		void *	buf,
		uint	len
	)

Read up to the specified number of characters from a loopback.

Parameters

devptr	Loopback device to read from.
buf	Buffer into which to place the read data.
len	Maximum number of characters to read.

Returns: Returns the number of characters read, which may be less than len if EOF or a read error occurs. Alternatively, if the loopback device is not open, returns SYSERR.

devcall loopbackWrite	(	device *	devptr,
		const void *	buf,
		uint	len
	)

Write data to the loopbock device.

Parameters

devptr	Pointer to the loopback device to write to.
buf	Buffer of data to write.
len	Number of bytes of data to write.

Returns: On success, returns the number of bytes written, which may be less than len in the event of a write error. Alternatively, SYSERR is returned if the loopback device is not open or if a write error occurred before any data at all was successfully written.

Functions

Detailed Description

Function Documentation