table of contents
IEEE1284_TRANSFER(3) | Functions | IEEE1284_TRANSFER(3) |
NAME¶
ieee1284_nibble_read, ieee1284_compat_write, ieee1284_byte_read, ieee1284_epp_read_data, ieee1284_epp_write_data, ieee1284_epp_read_addr, ieee1284_epp_write_addr, ieee1284_ecp_read_data, ieee1284_ecp_write_data, ieee1284_ecp_read_addr, ieee1284_ecp_write_addr - data transfer functionsSYNOPSIS¶
#include <ieee1284.h>
ssize_t
ieee1284_nibble_read(struct parport *port,
int flags, char *buffer,
size_t len);
ssize_t
ieee1284_compat_write(struct parport *port,
int flags,
const char *buffer,
size_t len);
ssize_t
ieee1284_byte_read(struct parport *port,
int flags, char *buffer,
size_t len);
ssize_t
ieee1284_epp_read_data(struct parport *port,
int flags, char *buffer,
size_t len);
ssize_t
ieee1284_epp_write_data(struct parport *port,
int flags,
const char *buffer,
size_t len);
ssize_t
ieee1284_epp_read_addr(struct parport *port,
int flags, char *buffer,
size_t len);
ssize_t
ieee1284_epp_write_addr(struct parport *port,
int flags,
const char *buffer,
size_t len);
ssize_t
ieee1284_ecp_read_data(struct parport *port,
int flags, char *buffer,
size_t len);
ssize_t
ieee1284_ecp_write_data(struct parport *port,
int flags,
const char *buffer,
size_t len);
ssize_t
ieee1284_ecp_read_addr(struct parport *port,
int flags, char *buffer,
size_t len);
ssize_t
ieee1284_ecp_write_addr(struct parport *port,
int flags,
const char *buffer,
size_t len);
DESCRIPTION¶
This set of functions is for tranferring bytes in the relevant transfer mode. For ECP and EPP modes two types of transfer are possible: data and address (usually referred to as channel in ECP). The supplied port must be a claimed port. The supplied buffer must be at least len bytes long. When reading, the transferred data is stored in the buffer; when writing the data to be transferred is taken from the buffer. For reads (peripheral to host): if no data is available and F1284_NONBLOCK is not in effect, the inactivity timer is started. If data becomes available before the inactivity time-out elapses it is read; otherwise the return value will be E1284_TIMEDOUT. For writes (host to peripheral): if the peripheral is not willing to accept data and F1284_NONBLOCK is not in effect, the inactivity timer is started. If the peripheral indicates that it is willing to accept data before the inactivity time-out elapses it is sent; otherwise the return value will be E1284_TIMEDOUT The flags may alter the behaviour slightly: F1284_NONBLOCKFor reads (peripheral to host): if no data is available,
return immediately (with E1284_TIMEDOUT).
For writes (host to peripheral): if the peripheral is not willing to accept
data, return immediately (with E1284_TIMEDOUT).
F1284_SWE
Don't use hardware assistance for the transfer, but
instead set the parallel port pins according to the wire protocol.
F1284_RLE (for ECP only)
Use run length encoding. If the peripheral is in ECP mode
with RLE, calls to ieee1284_ecp_read_data must set this flag in
order for the RLE from the peripheral to be interpreted correctly, and calls
to ieee1284_ecp_write_data may set this flag in order to take
advantage of RLE.
F1284_FASTEPP (for EPP only)
Use multi-byte transfers. Several bytes at a time are
transferred using hardware assistance, if supporting hardware is present. The
price of this increased speed is that the return value will be less reliable
when this flag is used.
For ECP mode, a given direction is in force at any particular time, and it is up
to the application to ensure that it is only writing when in forward mode, and
reading when in reverse mode.
RETURN VALUE¶
The return value is the number of bytes successfully transferred or, if negative, one of: E1284_NOTIMPLThis transfer mode and flags combination is not yet
implemented in libieee1284.
E1284_TIMEDOUT
Timed out waiting for peripheral to handshake.
E1284_NOMEM
Not enough memory is available.
E1284_SYS
There was a problem at the operating system level. The
global variable errno has been set appropriately.
E1284_INVALIDPORT
The port parameter is invalid (for instance,
perhaps the port is not claimed).
If any bytes are successfully transferred, that number is returned. An error is
returned only if no bytes are transferred.
For host-to-peripheral transfers, all data is at the peripheral by the time the
call returns.
SEE ALSO¶
ieee1284_ecp_fwd_to_rev(3)AUTHOR¶
Tim Waugh <twaugh@redhat.com>- Author.
COPYRIGHT¶
Copyright © 2001-2003 Tim Waugh09/18/2007 |