int ieee1284_negotiate (struct parport *port, int mode);
void ieee1284_terminate (struct parport *port);
DESCRIPTION
These functions are for negotiating to and terminating from IEEE 1284 data transfer modes. The default mode is called compatibility mode, or in other words normal printer protocol. It is a host-to-peripheral mode only. There are special modes that allow peripheral-to-host transfer as well, which may be negotiated to using ieee1284_negotiate. IEEE 1284 negotiation is a process by which the host requests a transfer mode and the peripheral accepts or rejects it. An IEEE 1284-compliant device will require a successful negotiation to a particular mode before it is used for data transfer (but simpler devices may not if they only speak one transfer mode).
To terminate the special mode and go back to compatilibity mode use ieee1284_terminate.
These functions act on the parallel port associated with port, which must be claimed.
With a device strictly complying to IEEE 1284 you will need to call ieee1284_terminate in between any two calls to ieee1284_negotiate for modes other than M1284_COMPAT.
AVAILABLE MODES
Uni-directional modes
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M1284_COMPAT: Compatibility mode. Normal printer protocol. This is not a negotiated mode, but is the default mode in absence of negotiation. ieee1284_negotiate(port, M1284_COMPAT) is equivalent to ieee1284_terminate(port). This host-to-peripheral mode is used for sending data to printers, and is historically the mode that has been used for that before IEEE 1284.
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M1284_NIBBLE: Nibble mode. This peripheral-to-host mode uses the status lines to read data from the peripheral four bits at a time.
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M1284_BYTE: Byte mode. This peripheral-to-host mode uses the data lines in reverse mode to read data from the peripheral a byte at a time.
Bi-directional modes
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M1284_ECP: ECP mode. On entry to ECP mode it is a host-to-peripheral (i.e. forward) mode, but it may be set to reverse mode using ieee1284_ecp_fwd_to_rev(3). It is common for PC hardware to provide assistance with this mode by the use of a FIFO which the host (or, in reverse mode, the peripheral) may fill, so that the hardware can do the handshaking itself.
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M1284_EPP: EPP mode. In this bi-directional mode the direction of data transfer is signalled at each byte.
Mode variations
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M1284_FLAG_DEVICEID: Device ID retrieval. This flag may be combined with a nibble, byte, or ECP mode to notify the device that it should send its IEEE 1284 Device ID when asked for data.
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M1284_BECP: Bounded ECP is a modification to ECP that makes it more robust at the point that the direction is changed. (Unfortunately it is not yet implemented in the Linux kernel driver.)
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M1284_ECPRLE: ECP with run length encoding. In this mode, consecutive data bytes of the same value may be transferred in only a few cycles.
RETURN VALUE
E1284_OK
The negotiation was successful.
E1284_NOTAVAIL
Negotiation is not available with this port type.
E1284_REJECTED
Negotiation was rejected by the peripheral.
E1284_NEGFAILED
Negotiation failed for some reason. Perhaps the device is not IEEE 1284 compliant.
E1284_SYS
A system error occured during negotiation.
E1284_INVALIDPORT
The port parameter is invalid (for instance, perhaps the port is not claimed).
