shithub: 9ferno

ref: 6966e8d72ae8fb72ebf98909acbd464aff84a3cc

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.TH PNP 3
.SH NAME
pnp, pci \- Plug 'n' Play ISA and PCI Interfaces
.SH SYNOPSIS
.nf
.B bind -a '#$' /dev

.BI /dev/pci/ bus\fL.\fPdev\fL.\fPfn ctl
.BI /dev/pci/ bus\fL.\fPdev\fL.\fPfn raw

.BI /dev/pnp/ctl
.BI /dev/pnp/csn n ctl
.BI /dev/pnp/csn n raw
\&...

.fi
.SH DESCRIPTION
This device provides a limited interface to the PCI bus and
Plug 'n' Play ISA devices.
Both are present on most PC platforms; on others, only the
.B pci
interface is present (because there is no ISA bus).
.SS PCI Interface
.PP
PCI devices are addressed logically by a bus number,
a device number on that bus, and a function number
within the device.
The set of all such device functions may be enumerated
by traversing the
.B /dev/pci
directory; the driver serves two files for each function.
These are a control file
.RL ( /dev/pci/\fIbus\fP.\fIdev\fP.\fIfn\fPctl )
which may be read for a textual summary of the device function,
and a `raw' file
.RL ( /dev/pci/\fIbus\fP.\fIdev\fP.\fIfn\fPraw )
which may be read to obtain the raw contents of PCI configuration space.
.PP
The first field of a PCI control file contains the class, sub-class and
programming interface values for the device function, expressed
as 2-digit hexadecimal values, and separated by periods.
The second field yields the vendor ID and device ID, each as 4-digit
hex numbers, separated by a slash.
The third field is the associated interrupt line in decimal.
The remainder of the line enumerates any valid base address
registers for the function, using two fields for each.
In the first field, the index of the register is followed by
a colon, and then the value of the register itself.
The following field gives the associated size of the memory
(or I/O space) that is mapped by the register.
.SS Plug 'n' Play
.PP
Plug 'n' Play ISA devices are discovered by sending a fixed `unlock' sequence
over an I/O port, and then reading back data from another port.
An arbitration algorithm is used to separate out the individual
cards and enumerate them in turn.
Each card is assigned a unique number, called a CSN, in the range 1-255 as a
result of enumeration.
Cards also have a fixed 64 bit identification number, set by the
manufacturer, which is used by the arbitration algorithm to
resolve conflicts.
The first 32 bits describe the type of the card, and the second
32 bits form a serial number for the particular instance of that card type.
When formatted textually, it appears as 3 upper-case letters
(typically representing the manufacturer),
followed by 4 hex digits, then a period, then 8 hex digits.
The substring before the period is the card type, and the substring
after the period is the serial number.
.PP
The enumeration algorithm needs to be enabled by specifying the
port number to write the unlock sequence out on.
This can be configured to take place at boot time by adding a line
like the following to
.IR plan9.ini :
.IP
.EX
pnp0=port=0x203
.EE
.PP
Here
.B port
should be chosen to not conflict with any existing devices.
It must be in the range
.BR 0x203-0x3ff .
Alternatively, one can use the following command:
.IP
.EX
echo port 0x203 >/dev/pnp/ctl
.EE
.PP
Note that a side-effect of PnP enumeration is to reset the configuration
state of all such cards; any settings made by a Plug and Play BIOS will be lost.
Reading the file
.B /dev/pnp/ctl
returns one of the strings
.B "enabled\fI port\fP"
or
.BR "disabled" .
.PP
For each enumerated card, two files are served in
.BR /dev/pnp .
A control file
.RL ( /dev/pnp/csn\fIn\fPctl )
may be read to determine the ID of the card, and a raw file
.RL ( /dev/pnp/csn\fIn\fPraw )
may be read to obtain the configuration data associated with the card.
It is intended that the control file should take commands which set the
various configurable resources of the card, but this has not been
implemented yet.
.PP
A mechanism is provided for configuring cards via
.IR plan9.ini (10.6).
A line of the form
.BI pnp n = "idstring ..."
will cause the driver to look for the card named by
.I idstring
and, if found, assign it the CSN
.IR n .
The intention is that
any additional text after the idstring is interpreted as if it
was written to the card's
.B ctl
file, but this is not yet implemented.
.SH EXAMPLES
.PP
To list all PCI functions:
.IP
.EX
cat /dev/pci/*ctl
.EE
.PP
To find just the PCI video card (class 3):
.IP
.EX
grep '^03' /dev/pci/*ctl
.EE
.SH SOURCE
.B /os/pc/devpnp.c
.br
.B /os/port/devpci.c
.SH BUGS
There is currently no way to write to PCI configuration space,
or to perform reads of less than 32 bits.
Access to the I/O and memory regions of a PCI device is not provided.
.PP
The ability to set a Plug 'n' Play card's configurable settings has not been
implemented.
.PP
There should be a user program for identifying and configuring
Plug 'n' Play cards.