<s>
In	O
computing	O
,	O
the	O
Windows	B-Application
Driver	I-Application
Model	I-Application
(	O
WDM	O
)	O
also	O
known	O
at	O
one	O
point	O
as	O
the	O
Win32	B-Application
Driver	I-Application
Model	I-Application
is	O
a	O
framework	O
for	O
device	B-Application
drivers	I-Application
that	O
was	O
introduced	O
with	O
Windows	B-Device
98	I-Device
and	O
Windows	B-Application
2000	I-Application
to	O
replace	O
VxD	B-Application
,	O
which	O
was	O
used	O
on	O
older	O
versions	O
of	O
Windows	O
such	O
as	O
Windows	B-Application
95	I-Application
and	O
Windows	B-Application
3.1	I-Application
,	O
as	O
well	O
as	O
the	O
Windows	O
NT	O
Driver	O
Model	O
.	O
</s>
<s>
WDM	O
drivers	O
are	O
layered	O
in	O
a	O
stack	O
and	O
communicate	O
with	O
each	O
other	O
via	O
I/O	B-Device
request	I-Device
packets	I-Device
(	O
IRPs	O
)	O
.	O
</s>
<s>
The	O
Microsoft	B-Application
Windows	I-Application
Driver	O
Model	O
unified	O
driver	O
models	O
for	O
the	O
Windows	O
9x	O
and	O
Windows	O
NT	O
product	O
lines	O
by	O
standardizing	O
requirements	O
and	O
reducing	O
the	O
amount	O
of	O
code	O
that	O
needed	O
to	O
be	O
written	O
.	O
</s>
<s>
WDM	O
drivers	O
will	O
not	O
run	O
on	O
operating	O
systems	O
earlier	O
than	O
Windows	B-Device
98	I-Device
or	O
Windows	B-Application
2000	I-Application
,	O
such	O
as	O
Windows	B-Application
95	I-Application
(	O
before	O
the	O
OSR2	O
update	O
that	O
sideloads	O
the	O
WDM	O
model	O
)	O
,	O
Windows	O
NT	O
4.0	O
and	O
Windows	B-Application
3.1	I-Application
.	O
</s>
<s>
By	O
conforming	O
to	O
WDM	O
,	O
drivers	O
can	O
be	O
binary	B-General_Concept
compatible	I-General_Concept
and	O
source-compatible	B-General_Concept
across	O
Windows	B-Device
98	I-Device
,	O
Windows	B-Device
98	I-Device
Second	O
Edition	O
,	O
Windows	B-Device
Me	I-Device
,	O
Windows	B-Application
2000	I-Application
,	O
Windows	B-Application
XP	I-Application
,	O
Windows	B-Application
Server	I-Application
2003	I-Application
and	O
Windows	B-Application
Vista	I-Application
(	O
for	O
backwards	B-General_Concept
compatibility	I-General_Concept
)	O
on	O
x86-based	O
computers	O
.	O
</s>
<s>
WDM	O
drivers	O
are	O
designed	O
to	O
be	O
forward-compatible	B-General_Concept
so	O
that	O
a	O
WDM	O
driver	O
can	O
run	O
on	O
a	O
version	O
of	O
Windows	O
newer	O
than	O
what	O
the	O
driver	O
was	O
initially	O
written	O
for	O
,	O
but	O
doing	O
that	O
would	O
mean	O
that	O
the	O
driver	O
cannot	O
take	O
advantage	O
of	O
any	O
new	O
features	O
introduced	O
with	O
the	O
new	O
version	O
.	O
</s>
<s>
WDM	O
is	O
generally	O
not	O
backward-compatible	B-General_Concept
,	O
that	O
is	O
,	O
a	O
WDM	O
driver	O
is	O
not	O
guaranteed	O
to	O
run	O
on	O
any	O
older	O
version	O
of	O
Windows	O
.	O
</s>
<s>
For	O
example	O
,	O
Windows	B-Application
XP	I-Application
can	O
use	O
a	O
driver	O
written	O
for	O
Windows	B-Application
2000	I-Application
but	O
will	O
not	O
make	O
use	O
of	O
any	O
of	O
the	O
new	O
WDM	O
features	O
that	O
were	O
introduced	O
in	O
Windows	B-Application
XP	I-Application
.	O
</s>
<s>
However	O
,	O
a	O
driver	O
written	O
for	O
Windows	B-Application
XP	I-Application
may	O
or	O
may	O
not	O
load	O
on	O
Windows	B-Application
2000	I-Application
.	O
</s>
<s>
WDM	O
exists	O
in	O
the	O
intermediary	O
layer	O
of	O
Windows	B-Application
2000	I-Application
kernel-mode	B-Operating_System
drivers	O
and	O
was	O
introduced	O
to	O
increase	O
the	O
functionality	O
and	O
ease	O
of	O
writing	O
drivers	O
for	O
Windows	O
.	O
</s>
<s>
Although	O
WDM	O
was	O
mainly	O
designed	O
to	O
be	O
binary	O
and	O
source	B-General_Concept
compatible	I-General_Concept
between	O
Windows	B-Device
98	I-Device
and	O
Windows	B-Application
2000	I-Application
,	O
this	O
may	O
not	O
always	O
be	O
desired	O
and	O
so	O
specific	O
drivers	O
can	O
be	O
developed	O
for	O
either	O
operating	O
system	O
.	O
</s>
<s>
With	O
the	O
Windows	O
Drivers	O
Model	O
(	O
WDM	O
)	O
for	O
devices	O
Microsoft	O
implements	O
an	O
approach	O
to	O
kernel	O
mode	O
drivers	O
that	O
is	O
unique	O
to	O
Windows	B-Application
operating	I-Application
systems	I-Application
.	O
</s>
<s>
WDM	O
implements	O
a	O
layered	O
architecture	O
for	O
device	B-Application
drivers	I-Application
,	O
and	O
every	O
device	O
of	O
a	O
computer	O
is	O
served	O
by	O
a	O
stack	O
of	O
drivers	O
.	O
</s>
<s>
WDM	O
defines	O
architecture	O
and	O
device	O
procedures	O
for	O
a	O
range	O
of	O
devices	O
,	O
such	O
as	O
display	O
and	O
the	O
network	B-Protocol
card	I-Protocol
,	O
known	O
as	O
Network	B-Application
Driver	I-Application
Interface	I-Application
Specification	I-Application
(	O
NDIS	O
)	O
.	O
</s>
<s>
In	O
the	O
NDIS	O
architecture	O
the	O
layered	O
network	O
drivers	O
include	O
lower-level	O
drivers	O
that	O
manage	O
the	O
hardware	O
and	O
upper-level	O
drivers	O
that	O
implement	O
network	O
data	O
transport	O
,	O
such	O
as	O
the	O
Transmission	B-Protocol
Control	I-Protocol
Protocol	I-Protocol
(	O
TCP	O
)	O
.	O
</s>
<s>
While	O
WDM	O
defines	O
three	O
types	O
of	O
device	B-Application
drivers	I-Application
,	O
not	O
all	O
driver	O
stacks	O
for	O
a	O
given	O
device	O
contain	O
all	O
types	O
of	O
device	B-Application
drivers	I-Application
.	O
</s>
<s>
The	O
three	O
WDM	O
device	B-Application
driver	I-Application
types	O
are	O
:	O
</s>
<s>
Bus	B-General_Concept
driver	O
:	O
For	O
every	O
bus	B-General_Concept
on	O
the	O
mainboard	O
there	O
is	O
a	O
one	O
bus	B-General_Concept
driver	O
,	O
with	O
the	O
primary	O
responsibility	O
for	O
the	O
identification	O
of	O
all	O
devices	O
connected	O
to	O
that	O
bus	B-General_Concept
and	O
responding	O
to	O
plug	B-Device
and	I-Device
play	I-Device
events	O
.	O
</s>
<s>
Microsoft	O
will	O
provide	O
bus	B-General_Concept
drivers	O
as	O
part	O
of	O
the	O
operating	O
system	O
,	O
such	O
as	O
PCI	B-Protocol
,	O
PnPISA	B-Device
,	O
SCSI	B-Architecture
,	O
USB	B-Protocol
and	O
FireWire	B-Protocol
.	O
</s>
<s>
Function	O
drivers	O
are	O
written	O
by	O
the	O
device	O
vendors	O
,	O
and	O
for	O
their	O
interaction	O
with	O
the	O
hardware	O
they	O
depend	O
on	O
a	O
specific	O
bus	B-General_Concept
driver	O
being	O
present	O
in	O
the	O
Windows	B-Application
operating	I-Application
system	I-Application
.	O
</s>
<s>
Filter	O
driver	O
:	O
This	O
driver	O
is	O
optional	O
,	O
and	O
can	O
modify	O
the	O
behaviour	O
of	O
a	O
device	O
,	O
such	O
as	O
input	B-General_Concept
and	I-General_Concept
output	I-General_Concept
requests	O
.	O
</s>
<s>
Function	O
drivers	O
and	O
bus	B-General_Concept
drivers	O
are	O
often	O
implemented	O
as	O
driver/minidriver	O
pairs	O
,	O
which	O
in	O
practice	O
is	O
either	O
a	O
class	O
or	O
miniclass	O
,	O
or	O
a	O
port	O
or	O
miniport	O
pair	O
.	O
</s>
<s>
Bus	B-General_Concept
drivers	O
for	O
devices	O
attached	O
to	O
a	O
bus	B-General_Concept
are	O
implemented	O
as	O
class	O
drivers	O
and	O
are	O
hardware-agnostic	O
.	O
</s>
<s>
Windows	B-Application
operating	I-Application
systems	I-Application
include	O
a	O
number	O
of	O
class	O
drivers	O
,	O
such	O
as	O
the	O
kbdclass.sys	O
driver	O
for	O
keyboards	O
.	O
</s>
<s>
Port	O
drivers	O
support	O
general	O
input/output	B-General_Concept
(	O
I/O	B-General_Concept
)	O
operations	O
for	O
a	O
peripheral	O
hardware	O
interface	O
.	O
</s>
<s>
The	O
core	O
functionality	O
of	O
port	O
drivers	O
is	O
mandated	O
by	O
the	O
operating	O
system	O
,	O
and	O
Windows	B-Application
operating	I-Application
systems	I-Application
integrate	O
a	O
variety	O
of	O
port	O
drivers	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
i8042prt.sys	O
port	O
driver	O
for	O
the	O
8042	O
microcontroller	O
connects	O
PS/2	B-Device
keyboards	O
to	O
the	O
mainboard	O
peripheral	O
bus	B-General_Concept
.	O
</s>
<s>
Each	O
driver	O
that	O
processes	O
an	O
I/O	B-General_Concept
request	O
for	O
a	O
device	O
has	O
a	O
corresponding	O
object	O
,	O
which	O
is	O
loaded	O
into	O
main	O
memory	O
.	O
</s>
<s>
A	O
device	O
object	O
is	O
created	O
by	O
the	O
Windows	B-Application
operating	I-Application
system	I-Application
from	O
the	O
associated	O
device	O
class	O
.	O
</s>
<s>
In	O
the	O
WDM	O
driver	O
stack	O
,	O
the	O
filter	O
driver	O
device	O
object	O
,	O
known	O
as	O
the	O
upper	O
filter	O
,	O
will	O
receive	O
an	O
I/O	B-Device
request	I-Device
packet	I-Device
(	O
IRP	O
)	O
for	O
a	O
device	O
from	O
the	O
I/O	B-General_Concept
manager	O
.	O
</s>
<s>
Then	O
the	O
IRP	O
may	O
be	O
passed	O
down	O
to	O
the	O
bus	B-General_Concept
driver	O
,	O
which	O
operates	O
as	O
the	O
physical	O
device	O
object	O
.	O
</s>
<s>
The	O
bus	B-General_Concept
driver	O
object	O
is	O
at	O
the	O
bottom	O
of	O
the	O
driver	O
stack	O
,	O
and	O
interacts	O
with	O
the	O
hardware	B-Operating_System
abstraction	I-Operating_System
layer	I-Operating_System
,	O
which	O
is	O
part	O
of	O
the	O
Windows	B-Application
operating	I-Application
system	I-Application
kernel	O
and	O
allows	O
Windows	B-Application
operating	I-Application
systems	I-Application
to	O
run	O
on	O
a	O
variety	O
of	O
processors	O
,	O
different	O
memory	B-General_Concept
management	I-General_Concept
unit	I-General_Concept
architectures	O
,	O
and	O
a	O
variety	O
of	O
computer	O
systems	O
with	O
different	O
I/O	B-General_Concept
bus	I-General_Concept
architectures	O
.	O
</s>
<s>
The	O
execution	O
of	O
an	O
IRP	O
is	O
finished	O
when	O
any	O
of	O
the	O
driver	O
objects	O
in	O
the	O
stack	O
returns	O
the	O
request	O
back	O
to	O
the	O
I/O	B-General_Concept
manager	O
,	O
with	O
the	O
result	O
and	O
a	O
status	O
flag	O
.	O
</s>
<s>
In	O
Windows	B-Application
operating	I-Application
systems	I-Application
,	O
drivers	O
are	O
implemented	O
as	O
Dynamic	O
Link	O
Libraries	O
.DLL	O
or	O
.SYS	O
files	O
.	O
</s>
<s>
WDM	O
compliant	O
drivers	O
must	O
follow	O
rules	O
of	O
design	O
,	O
initialisation	O
,	O
plug-and-play	B-Device
,	O
power	O
management	O
and	O
memory	O
allocation	O
.	O
</s>
<s>
In	O
practice	O
WDM	O
driver	O
programmers	O
reuse	O
large	O
pieces	O
of	O
code	O
when	O
building	O
new	O
object-oriented	B-Language
drivers	O
.	O
</s>
<s>
A	O
device	B-Application
driver	I-Application
that	O
is	O
not	O
designed	O
for	O
a	O
specific	O
hardware	O
component	O
may	O
allow	O
another	O
device	O
to	O
function	O
.	O
</s>
<s>
However	O
,	O
installing	O
the	O
wrong	O
driver	O
for	O
a	O
device	O
will	O
mean	O
that	O
the	O
full	O
functionality	O
of	O
the	O
device	O
can	O
not	O
be	O
used	O
,	O
and	O
may	O
result	O
in	O
poor	O
performance	O
and	O
the	O
destabilization	O
of	O
the	O
Windows	B-Application
operating	I-Application
system	I-Application
.	O
</s>
<s>
Hardware	O
device	O
vendors	O
may	O
release	O
updated	O
device	B-Application
drivers	I-Application
for	O
particular	O
Windows	B-Application
operating	I-Application
systems	I-Application
,	O
to	O
improve	O
performance	O
,	O
add	O
functionality	O
or	O
fix	O
bugs	B-Error_Name
.	O
</s>
<s>
If	O
a	O
device	O
is	O
not	O
working	O
as	O
expected	O
the	O
latest	O
device	B-Application
drivers	I-Application
should	O
be	O
downloaded	O
from	O
the	O
vendor	O
website	O
and	O
installed	O
.	O
</s>
<s>
Device	B-Application
drivers	I-Application
are	O
designed	O
for	O
particular	O
Windows	B-Application
operating	I-Application
system	I-Application
versions	O
,	O
and	O
device	B-Application
drivers	I-Application
for	O
a	O
previous	O
version	O
of	O
Windows	O
may	O
not	O
work	O
correctly	O
or	O
at	O
all	O
with	O
other	O
versions	O
.	O
</s>
<s>
Because	O
many	O
device	B-Application
drivers	I-Application
run	O
in	O
kernel	O
mode	O
installing	O
drivers	O
for	O
a	O
previous	O
operating	O
system	O
version	O
may	O
destabilise	O
the	O
Windows	B-Application
operating	I-Application
system	I-Application
.	O
</s>
<s>
Migrating	O
a	O
computer	O
to	O
a	O
higher	O
version	O
of	O
a	O
Windows	B-Application
operating	I-Application
system	I-Application
therefore	O
requires	O
that	O
new	O
device	B-Application
drivers	I-Application
are	O
installed	O
for	O
all	O
hardware	O
components	O
.	O
</s>
<s>
Finding	O
up	O
to	O
date	O
device	B-Application
drivers	I-Application
and	O
installing	O
them	O
for	O
Windows	B-Operating_System
10	I-Operating_System
has	O
introduced	O
complications	O
into	O
the	O
migration	O
process	O
.	O
</s>
<s>
Common	O
device	B-Application
driver	I-Application
compatibility	O
issues	O
include	O
:	O
a	O
32-bit	O
device	B-Application
driver	I-Application
is	O
required	O
for	O
a	O
32-bit	B-Application
Windows	B-Application
operating	I-Application
system	I-Application
,	O
and	O
a	O
64-bit	B-Device
device	B-Application
driver	I-Application
is	O
required	O
for	O
a	O
64-bit	B-Device
Windows	B-Application
operating	I-Application
system	I-Application
.	O
</s>
<s>
64-bit	B-Device
device	B-Application
drivers	I-Application
must	O
be	O
signed	O
by	O
Microsoft	O
,	O
because	O
they	O
run	O
in	O
kernel	O
mode	O
and	O
have	O
unrestricted	O
access	O
to	O
the	O
computer	O
hardware	O
.	O
</s>
<s>
For	O
operating	O
systems	O
prior	O
to	O
Windows	B-Operating_System
10	I-Operating_System
Microsoft	O
allowed	O
vendors	O
to	O
sign	O
their	O
64-bit	B-Device
drivers	O
themselves	O
,	O
assuming	O
vendors	O
had	O
undertaken	O
compatibility	O
tests	O
.	O
</s>
<s>
However	O
,	O
Windows	B-Operating_System
10	I-Operating_System
64-bit	B-Device
drivers	O
now	O
need	O
to	O
be	O
signed	O
by	O
Microsoft	O
.	O
</s>
<s>
The	O
driver	O
installation	O
package	O
includes	O
all	O
files	O
in	O
the	O
.inf	O
directory	O
,	O
and	O
all	O
files	O
in	O
the	O
package	O
need	O
to	O
be	O
installed	O
,	O
otherwise	O
the	O
installation	O
of	O
the	O
device	B-Application
driver	I-Application
may	O
fail	O
.	O
</s>
<s>
For	O
operating	O
system	O
versions	O
before	O
Windows	B-Operating_System
10	I-Operating_System
not	O
all	O
files	O
necessary	O
for	O
the	O
driver	O
installation	O
were	O
included	O
in	O
the	O
package	O
,	O
as	O
this	O
requirement	O
was	O
not	O
consistently	O
enforced	O
.	O
</s>
<s>
Some	O
device	B-Application
driver	I-Application
installers	O
have	O
a	O
user	O
interface	O
GUI	B-Application
,	O
often	O
requiring	O
user	O
configuration	O
input	O
.	O
</s>
<s>
The	O
absence	O
of	O
a	O
user	O
interface	O
does	O
not	O
mean	O
that	O
the	O
installation	O
of	O
the	O
device	B-Application
driver	I-Application
is	O
not	O
successful	O
.	O
</s>
<s>
Besides	O
,	O
Windows	B-Operating_System
10	I-Operating_System
device	B-Application
drivers	I-Application
are	O
not	O
allowed	O
to	O
include	O
a	O
user	O
interface	O
.	O
</s>
<s>
The	O
Network	B-Application
Driver	I-Application
Interface	I-Application
Specification	I-Application
(	O
NDIS	O
)	O
10.x	O
is	O
used	O
for	O
network	O
devices	O
by	O
the	O
Windows	B-Operating_System
10	I-Operating_System
operating	O
system	O
.	O
</s>
<s>
Network	O
device	B-Application
drivers	I-Application
for	O
Windows	B-Application
XP	I-Application
use	O
NDIS	O
5.x	O
and	O
may	O
work	O
with	O
subsequent	O
Windows	B-Application
operating	I-Application
systems	I-Application
,	O
but	O
for	O
performance	O
reasons	O
network	O
device	B-Application
drivers	I-Application
should	O
implement	O
NDIS	O
6.0	O
or	O
higher	O
.	O
</s>
<s>
Similarly	O
,	O
WDDM	B-Device
is	O
the	O
driver	O
model	O
for	O
Windows	B-Application
Vista	I-Application
and	O
up	O
,	O
which	O
replaces	O
XPDM	O
used	O
in	O
graphics	O
drivers	O
.	O
</s>
<s>
The	O
Device	O
Manager	O
is	O
a	O
Control	O
Panel	O
applet	O
in	O
Microsoft	B-Application
Windows	I-Application
operating	I-Application
systems	I-Application
.	O
</s>
<s>
It	O
allows	O
users	O
to	O
view	O
and	O
modify	O
hardware	O
device	O
properties	O
,	O
and	O
is	O
also	O
the	O
primary	O
tool	O
to	O
manage	O
device	B-Application
drivers	I-Application
.	O
</s>
<s>
The	O
Windows	B-Application
Driver	I-Application
Model	I-Application
,	O
while	O
a	O
significant	O
improvement	O
over	O
the	O
VxD	B-Application
and	O
Windows	O
NT	O
Driver	O
Model	O
used	O
before	O
it	O
,	O
has	O
been	O
criticised	O
by	O
driver	B-Application
software	I-Application
developers	O
,	O
most	O
significantly	O
for	O
the	O
following	O
:	O
</s>
<s>
Interactions	O
with	O
power	O
management	O
events	O
and	O
plug	B-Device
and	I-Device
play	I-Device
are	O
difficult	O
.	O
</s>
<s>
This	O
can	O
lead	O
to	O
situations	O
where	O
Windows	O
machines	O
cannot	O
enter	O
or	O
exit	O
sleep	O
modes	O
correctly	O
due	O
to	O
bugs	B-Error_Name
in	O
driver	O
code	O
.	O
</s>
<s>
I/O	B-General_Concept
cancellation	O
is	O
difficult	O
to	O
get	O
right	O
.	O
</s>
<s>
There	O
is	O
no	O
support	O
for	O
writing	O
pure	O
user-mode	B-Operating_System
drivers	O
.	O
</s>
<s>
Because	O
of	O
these	O
issues	O
,	O
Microsoft	O
has	O
released	O
a	O
new	O
set	O
of	O
frameworks	O
on	O
top	O
of	O
WDM	O
,	O
called	O
the	O
Windows	B-Application
Driver	I-Application
Frameworks	I-Application
(	O
WDF	O
;	O
formerly	O
Windows	B-Application
Driver	I-Application
Foundation	I-Application
)	O
,	O
which	O
includes	O
Kernel-Mode	B-Application
Driver	I-Application
Framework	I-Application
(	O
KMDF	B-Application
)	O
and	O
User-Mode	B-Application
Driver	I-Application
Framework	I-Application
(	O
UMDF	B-Application
)	O
.	O
</s>
<s>
Windows	B-Application
Vista	I-Application
supports	O
both	O
pure	O
WDM	O
and	O
the	O
newer	O
WDF	O
.	O
</s>
<s>
KMDF	B-Application
is	O
also	O
available	O
for	O
download	O
for	O
Windows	B-Application
XP	I-Application
and	O
even	O
Windows	B-Application
2000	I-Application
,	O
while	O
UMDF	B-Application
is	O
available	O
for	O
Windows	B-Application
XP	I-Application
and	O
above	O
.	O
</s>
