FILES

/dev/lp*

AUTHORS

The printer driver was originally written by Jim Weigand and Linus Torvalds. It was further improved by Michael K. Johnson. The interrupt code was written by Nigel Gamble. Alan Cox modularized it. LPCAREFUL, LPABORT, LPGETSTATUS were added by Chris Metcalf.

SEE ALSO

mknod(1), chown(1), chmod(1), tunelp(8), lpcntl(8)

15 January 1995

mem, kmem, port

mem, kmem, port—System memory, kernel memory, and system ports

DESCRIPTION

mem is a character device file that is an image of the main memory of the computer. It can be used, for example, to examine (and even patch) the system.

Byte addresses in mem are interpreted as physical memory addresses. References to non-existent locations cause errors to be returned.

Examining and patching is likely to lead to unexpected results when read-only or write-only bits are present.

It is typically created by

mknod -m 660 /dev/mem c 1 1

chown root.mem /dev/mem

The file kmem is the same as mem, except that the kernel virtual memory rather than physical memory is accessed.

It is typically created by

mknod -m 640 /dev/kmem c 1 2

chown root.mem /dev/kmem

port is similar to mem, but the IO ports are accessed.

It is typically created by

mknod -m 660 /dev/port c 1 4

chown root.mem /dev/port

FILES

/dev/mem

/dev/kmem

/dev/port

SEE ALSO

mknod(1), chown(1), ioperm(2)

Linux, 21 November 1992

mouse

mouse—Serial mouse interface.

CONFIG

Serial mice are connected to a serial RS232/V24 dialout line; see cua(4) for a description.

DESCRIPTION

The pinout of the usual 9 pin plug as used for serial mice is

This is the specification; in fact, 9 V suffices with most mice.

The mouse driver can recognize a mouse by dropping RTS to low. About 14ms later, the mouse will send 0x4D on the data line. After a further 63ms, Microsoft-compatible mice will send 0x33. Other mice send different values.

The relative mouse movement is sent as dx (positive means right) and dy (positive means down). Various mice can operate at different speeds. To select speeds, cycle through the speeds 9600, 4800, 2400, and 1200 bits/sec, each time writing the two characters from the table below and waiting 0.1 seconds. The following table shows available speeds and the strings that select them:

The first byte of a data packet can be used to synchronization purposes.

MICROSOFT PROTOCOL

The Microsoft protocol uses 1 start bit, 7 data bits, no parity, and 1 stop bit at the speed of 1200 bits/sec. Data is sent to RxD in 3-byte packets. The dx and dy movements are sent as two's-complement, lb (rb) is set when the left (right) button is pressed:

Original Microsoft mice have only two buttons. However, there are some three-button mice that also use the Microsoft protocol. Pressing the third button is reported by sending a packet with zero movement and no buttons pressed.

MOUSESYSTEMS PROTOCOL

The MouseSystems protocol uses 1 start bit, 8 data bits, no parity, and 2 stop bits at the speed of 1200 bits/sec. Data is sent to RxD in 5-byte packets. dx is sent as the sum of the two two's-complement values, dy is send as negated sum of the two two's-complement values. lb (mb, rb) is cleared when the left (middle, right) button is pressed:

SUN PROTOCOL

The Sun protocol uses 1 start bit, 8 data bits, no parity, and 2 stop bits at the speed of 1200 bits/sec. Data is sent to RxD in 3-byte packets. dx is sent as single two's-complement value, dy as negated two's-complement value. lb (mb, rb) is cleared when the left (middle, right) button is pressed: