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.\" This code is derived from software contributed to Berkeley by
.\" the Systems Programming Group of the University of Utah Computer
.\" Science Department.
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.\"     from: @(#)hil.4	8.2 (Berkeley) 11/30/93
.\"
.Dd November 30, 1993
.Dt HIL 4 hp300
.Os
.Sh NAME
.Nm hil
.Nd Human Interface Link device driver
.Sh DESCRIPTION
The Human Interface Link
.Pq Tn HIL
is the interface used by the Series
300 computers to connect devices such as keyboards, mice, control knobs,
and
.Tn ID
modules to the machine.
.Pp
Special files
.Pa /dev/hil[1-7]
refer to physical
.Tn HIL
devices 1 through 7.
.Pa /dev/hil0
refers to the ``loop'' pseudo-device and is used for the queue
allocation commands described below.
In the current implementation,
there can only be one keyboard and it must be the first device
.Pq Li hil1 .
.Pp
The device file that corresponds to a particular
.Tn HIL
device is determined
by the order of the devices on the loop.
For instance, if the
.Tn ID
module
is the second physical device on the loop, then
.Pa /dev/hil2
is the special
file that should be used for communication with the module.
.Pp
Communication with an
.Tn HIL
device is begun with an
.Em open
system call.
A process may open a device already opened by another process unless
the process is operating in
.Tn HP-UX
compatibility mode
in which case it requires exclusive use of the device, or
another process has the device open and is using
.Tn HP-UX
style
device access (see
.Dv HILIOCHPUX
below).
.Pp
Input data from a device are obtained in one of two ways.
Processes may use an
.Tn HP-UX
style interface in which the
.Xr read 2
system call is used to get fixed-size input packets,
or they can use a
.Em shared-queue
interface.
The shared-queue interface avoids the system call overhead associated with
the
.Tn HP-UX
read interface by sharing a region of memory between the system
and a user process.
This region consists of a circular list of 255 event packets,
and a header containing the size of the queue, and its head and tail indices.
The system deposits event data at the tail of the queue,
a process extracts it from the head.
Extracting an event is done by copying it from the queue and then updating
the head appropriately (i.e.
head = (head + 1) % qsize).
It is up to the process to ensure that packets are removed from the
queue quickly enough to prevent the queue from filling.
The system, when it determines that the queue is full,
will ignore future packets from the device.
Devices are
.Em mapped
to queues via an
.Xr ioctl 2 .
More than one device can be mapped to a single queue and one device can
be mapped to several queues.
Queues are implicitly unmapped by a
.Xr fork 2
and thus,
cannot be shared between processes.
.Pp
Choosing the type of interface is done on a per device basis using
an
.Xr ioctl 2 ,
but each device can only have one interface at any given time.
.Pp
.Em Select
may be used with either interface to detect when input data are present.
With the read interface, selecting indicates when there is input for a
given device.
With the shared-queue interface, selecting on the loop pseudo-device
.Pq Li hil0
indicates when data are present from any device on any queue
while selecting on an individual device indicates when data are present
for that device on any queue.
.Pp
.Em Close
shuts down the file descriptor associated with the
.Tn HIL
device.
The last close (system-wide) of any device removes that device
from all queues it was mapped to while the last close of the loop
pseudo-device unmaps all devices and deallocates all queues.
.Pp
.Xr Ioctl 2
is used to control the
.Tn HIL
device.
The ioctl commands (see
.Aq Pa hpdev/hilioctl.h )
listed below are separated into two groups.
The first are those which provide functions identical to
.Tn HP-UX .
Refer to
.Xr hil 7
in the
.Tn HP-UX
documentation for more
complete descriptions of these ioctls.
The second set of ioctls are specific to this implementation and are
primarily related to the shared-queue interface.
.Bl -tag -width HILIOCARO
.It Dv HILIOCID
Identify and Describe
.Pp
The device will return up to 11 bytes of information describing the
type and characteristics of the device.
At the very least, 2 bytes of information,
the device
.Tn ID ,
and the Describe Record Header will be returned.
Identical to the
.Tn HP-UX
.Dv HILID
ioctl.
.It Dv HILIOCSC
Report Security Code
.Pp
Request the security code record from a device.
The security code can vary from 1 byte to 15, and is only supported by some
.Tn HIL
devices.
Identical to the
.Tn HP-UX
.Dv HILSC
ioctl.
.It Dv HILIOCRN
Report Name
.Pp
An ascii string of up to 15 bytes in length that describes the device
is returned.
Identical to the
.Tn HP-UX
.Dv HILRN
ioctl.
.It Dv HILIOCRS
Report Status
.Pp
An ascii string of up to 15 bytes in length that describes the current
status of the device is returned.
Identical to the
.Tn HP-UX
.Dv HILRS
ioctl.
.It Dv HILIOCED
Extended Describe
.Pp
Additional information of up to 15 bytes is returned describing the device.
This ioctl is similar to
.Tn HILIOCID ,
which must be used first
to determine if the device supports extended describe.
Identical to the
.Tn HP-UX
.Dv HILED
ioctl.
.It Dv HILIOCAROFF
Disable Auto Repeat
.Pp
Turn off auto repeat on the keyboard while it is in cooked mode.
Identical to the
.Tn HP-UX
.Dv HILDKR
ioctl.
.It Dv HILIOCAR1
Enable Auto Repeat
.Pp
Turn on auto repeat on the keyboard while it is in raw mode.
The repeat rate is set to 1/30th of a second.
Identical to the
.Tn HP-UX
.Dv HILER1
ioctl.
.It Dv HILIOCAR2
Enable Auto Repeat
.Pp
Turn on auto repeat on the keyboard while it is in raw mode.
The repeat rate is set to 1/60th of a second.
Identical to the
.Tn HP-UX
.Dv HILER2
ioctl.
.Pp
The following ioctls are specific to this implementation:
.It Dv HILIOCBEEP
Beep
.Pp
Generate a keyboard beep as defined by
.Ar arg .
.Ar Arg
is a pointer to two bytes of information,
the first is the duration of the beep (microseconds),
the second is the frequency of the beep.
.It Dv HILIOCALLOCQ
Allocate Queue
.Pp
Allocate and map into user space,
an
.Tn HILQ
structure as defined in
.Aq Pa hpdev/hilioctl.h .
.Ar Arg
is a pointer to a
.Ar hilqinfo
structure (also described in
.Aq Pa hpdev/hilioctl.h )
consisting of a
.Pa qid
and an
.Pa addr .
If
.Pa addr
is non-zero it specifies where in the address space to map the queue.
If zero, the system will select a convenient location and fill in
.Pa addr .
.Pa Qid
is filled in by the system and
is a small integer used to uniquely identify this queue.
This ioctl can only be issued to the loop pseudo-device.
.It Dv HILIOCFREEQ
Free Queue
.Pp
Release a previously allocated
.Tn HIL
event queue,
unmapping it from the user's address space.
.Ar Arg
should point to a
.Ar hilqinfo
structure which contains the
.Ar qid
of the queue to be released.
All devices that are currently mapped to the queue are unmapped.
This ioctl can only be issued to the loop pseudo-device.
.It Dv HILIOCMAPQ
Map Device to Queue
.Pp
Maps this device to a previously allocated
.Tn HIL
event queue.
.Ar Arg
is a pointer to an integer containing the
.Ar qid
of the queue.
Once a device is mapped to a queue,
all event information generated by the device will be placed
into the event queue at the tail.
.It Dv HILIOCUNMAPQ
Unmap Device from Queue
.Pp
Unmap this device from a previously allocated
.Tn HIL
event queue.
.Ar Arg
is a pointer to an integer containing the
.Ar qid
for the queue.
Future events from the device are no longer placed on the event queue.
.It Dv HILIOCHPUX
Use HP-UX Read Interface
.Pp
Use
.Tn HP-UX
semantics for gathering data from this device.
Instead of placing input events for the device on a queue,
they are placed, in
.Tn HP-UX
format, into a buffer from which they
can be obtained via
.Xr read 2 .
This interface is provided for backwards compatibility.
Refer to the
.Tn HP-UX
documentation for a description of the event packet.
.El
.Sh FILES
.Bl -tag -width /dev/hil[2-7] -compact
.It Pa /dev/hil0
.Tn HIL
loop pseudo device.
.It Pa /dev/hil1
.Tn HIL
keyboard device.
.It Pa /dev/hil[2-7]
Individual
.Tn HIL
loop devices.
.El
.Sh ERRORS
.Bl -tag -width [EINVAL]
.It Bq Er ENODEV
no such HIL loop device.
.It Bq Er ENXIO
HIL loop is inoperative.
.It Bq Er EBUSY
Another HP-UX process has the device open, or another
.Bx
process has the
device open, and is using it in
.Tn HP-UX
mode.
.It Bq Er EINVAL
Invalid
.Xr ioctl 2
specification.
.It Bq Er EMFILE
No more shared queues available.
.El