Man page 9 : parport_read

parport_read - read a block of data from a parallel port

ssize_t parport_read(struct parport *  port , void *  buffer , size_t  len );

port
    port to read from

buffer
    data buffer (in kernel space)

len
    number of bytes of data to transfer

This will read up to len bytes of buffer to the port specified, using the IEEE 1284 transfer mode most recently negotiated to (using parport_negotiate), as long as that mode supports reverse transfers (peripheral to host).

It is the callerAqs responsibility to ensure that the first len bytes of buffer are available to write to.

This function returns the number of bytes transferred (if zero or positive), or else an error code.