解析Linux下的并口编程(英文版)(2)

　　The ioctl parameter should be a pointer to an int; values for this are in incluce/linux/parport.h and include:

　　IEEE1284_MODE_COMPAT

　　IEEE1284_MODE_NIBBLE

　　IEEE1284_MODE_BYTE

　　IEEE1284_MODE_EPP

　　IEEE1284_MODE_ECP

　　The PPNEGOT ioctl actually does two things: it performs the on-the-wire negotiation, and it sets the behaviour of subsequent read/write calls so that they use that mode (but see PPSETMODE).

　　PPSETMODE

　　Sets which IEEE 1284 protocol to use for the read and write calls.

　　The ioctl parameter should be a pointer to an int.

　　PPGETMODE

　　Retrieves the current IEEE 1284 mode to use for read and write.

　　PPGETTIME

　　Retrieves the time-out value. The read and write calls will time out if the peripheral doesn't respond quickly enough. The PPGETTIME ioctl retrieves the length of time that the peripheral is allowed to have before giving up.

　　The ioctl parameter should be a pointer to a struct timeval.

　　PPSETTIME

　　Sets the time-out. The ioctl parameter should be a pointer to a struct timeval.

　　PPGETMODES

　　Retrieves the capabilities of the hardware (i.e. the modes field of the parport structure).

　　PPSETFLAGS

　　Sets flags on the ppdev device which can affect future I/O operations. Available flags are:

　　PP_FASTWRITE

　　PP_FASTREAD

　　PP_W91284PIC

　　PPWCONTROL

　　Sets the control lines. The ioctl parameter is a pointer to an unsigned char, the bitwise OR of the control line values in include/linux/parport.h.

　　PPRCONTROL

　　Returns the last value written to the control register, in the form of an unsigned char: each bit corresponds to a control line (although some are unused). The ioctl parameter should be a pointer to an unsigned char.

　　This doesn't actually touch the hardware; the last value written is remembered in software. This is because some parallel port hardware does not offer read access to the control register.

　　The control lines bits are defined in include/linux/parport.h:

　　PARPORT_CONTROL_STROBE

　　PARPORT_CONTROL_AUTOFD

　　PARPORT_CONTROL_SELECT

　　PARPORT_CONTROL_INIT

　　PPFCONTROL

　　Frobs the control lines. Since a common operation is to change one of the control signals while leaving the others alone, it would be quite inefficient for the user-land driver to have to use PPRCONTROL, make the change, and then use PPWCONTROL. Of course, ea