[RFC] userconf(4) modification

[tlaronde%kergis.com@localhost]

As stated in a message before, disabling, via userconf(4), all the
drmkms drivers can not rely on a pattern matching since, for historical
reasons (several versions of DRM), the namespace of the drivers is not
"ruled".

So I want to add a "group" member to the cfdata structure, with
modifications to config(1) to set it, in order to allow to disable
devices by a group name.

Additionnaly, because I had already implemented it, there is a pattern
matching feature too.

You will find attached the man page in order to be able to comment
about the proposed new syntax---supplementary syntax: it does not
replace the "legacy" one.
-- 
        Thierry Laronde <tlaronde +AT+ kergis +dot+ com>
                     http://www.kergis.com/
                    http://kertex.kergis.com/
Key fingerprint = 0FF7 E906 FBAF FE95 FD89  250D 52B1 AE95 6006 F40C

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.Dd November 1, 2023
.Dt USERCONF 4
.Os
.Sh NAME
.Nm userconf
.Nd in-kernel device configuration manager
.Sh SYNOPSIS
.Cd options USERCONF
.Sh DESCRIPTION
.Nm
is the in-kernel device configuration manager.
It is used to alter the kernel autoconfiguration framework at runtime.
.Nm
is activated from the boot loader by passing the
.Fl c
option to the kernel.
.Sh COMMAND SYNTAX
There is a subset of meta-commands described immediately below and
action commands, described after in separated sections, in two syntaxes: 
legacy and new, the new syntax extending the possibilities offered by
the legacy one.
.Pp
.Nm
has a
.Xr more 1 Ns -like
functionality; if a number of lines in a command's output exceeds the
number defined in the lines variable, then
.Nm
displays
.Dq "-- more --"
and waits for a response, which may be one of:
.Bl -tag -offset indent -width "<return>"
.It <return>
one more line.
.It <space>
one more page.
.It Ic q
abort the current command, and return to the command input mode.
.El
.Pp
The common meta-commands are the following:
.Bl -tag -width 5n
.It Ic lines Ar count
Specify the number of lines before more. A negative number suppresses
the paging.
.It Ic base Ar 8 | 10 | 16
Base for displaying large numbers.
.It Ic exit
A synonym for
.Ic quit .
.It Ic help
Display online help, including ranges of device number, list of
device names and groups.
.It Ic quit
Leave userconf.
.It Ic \&?
A synonym for
.Ic help .
.El
.Sh LEGACY SYNTAX AND COMMANDS
.Nm
supports the legacy syntax:
.Bd -ragged -offset indent
.Ic command Op Ar option
.Ed
.Pp
and offers the following commands:
.Bl -tag -width 5n
.It Ic change Ar devno | dev
Change devices.
.It Ic disable Ar devno | dev
Disable devices.
.It Ic enable Ar devno | dev
Enable devices.
.It Ic find Ar devno | dev
Find devices.
.It Ic list
List current configuration.
.El
.Sh NEW SYNTAX AND COMMANDS
.Nm
supports the new syntax:
.Bd -ragged -offset indent
.Ic command Ar property Li \&= Ar expression
.Ed
.Pp
The
.Li \&=
has to be interpreted as meaning: defines the collection of devices on
which to apply the command with devices whose stated property matches
the expression.
.Pp
The commands are the following (same as with legacy syntax):
.Bl -tag -width 7n
.It Ic change
Change devices.
.It Ic disable
Disable devices.
.It Ic enable
Enable devices.
.It Ic find
Find devices.
.It Ic list
List devices
.El
.Pp
A
.Ar property
is one of the literals
.Bl -tag -width 5n
.It Li devno
the index number of the device in the cfdata vector. The expression
shall be a positive or nul integer value, less than the cardinal of
devices in the cfdata vector.
.It Li name
the driver name. The expression shall be a string one (see below).
.It Li group
the group the device belongs to. The expression shall be a string one
(see below).
.El
.Ss STRING EXPRESSION
A string expression is whether a literal string enclosed between double
quotes
.Li \&"
or a pattern enclosed between slashes
.Li \&/ .
.Pp
With a pattern, the string is searched as a fixed substring (there is
neither a wildcard special character, nor ranges or counts etc.), that
can be anchored at the beginning of the string to match against with a
caret
.Li \&^
and/or at the end of the string to match against with a dollar
.Li \&$ .
.Pp
Hence the literal string:
.Li \&"foo\&"
will have the same effect as the anchored pattern:
.Li /^foo$/ .
.Pp
A string expression can be suffixed with a
.Li \&*
meaning to select devices matching the string only if they are STARred
ones. Examples:
.Li \&"foobar\&"*
or
.Li /^foo/*
(the pattern in this example will eventually match more than the
literal string).
.Sh EXAMPLES
Disabling all the devices belonging to the
.Li \&"drmkms\&"
group:
.Pp
.Dl disable group = \&"drmkms\&"
.Pp
Listing all the devices whose name matches
.Li usb
at the beginning of the name:
.Pp
.Dl list name = /^usb/
.Sh FILES
.Bl -item
.It
.Pa sys/sys/devices.h
.It
.Pa sys/sys/userconf.h
.It
.Pa sys/kern/subr_userconf.c
.El
.Sh HISTORY
The
.Nm
framework first appeared in
.Ox 2.0 ,
and was then integrated into
.Nx 1.6 .
.Sh AUTHORS
The
.Nm
framework was written by
.An Mats O Jansson
.Aq Mt moj%stacken.kth.se@localhost .
.Pp
The new syntax and the groups handling were added by
.An Thierry Laronde
.Aq tlaronde%kergis.com@localhost .