NetBSD/share/man/man9/vcons.9

.\" $NetBSD: vcons.9,v 1.1 2006/02/12 23:06:43 macallan Exp $
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.Dd February 12, 2006
.Dt VCONS 9
.Os
.Sh NAME
.Nm vcons
.Nd a generic virtual console framework
.Sh SYNOPSIS
.In wscons/wsdisplay_vconsvar.h
.Ft int
.Fn vcons_init "struct vcons_data *vd" "void *cookie" \
"struct wsscreen_descr *desc" "struct wsdisplay_accessops *accops"
.Ft int	
.Fn vcons_init_screen "struct vcons_data *vd" "struct vcons_screen *scr" \
"int exists" "long *defattr"
.Ft void
.Fn vcons_redraw_screen "struct vcons_screen *scr"
.Sh DESCRIPTION
These functions are used to setup and control the generic virtual console framework
.Pp
.\"
The
.Fn vcons_init
function initializes the framework, it needs to be called for each driver that's going
to use vcons. 
.Pp
.Fn vcons_init_screen
adds a virtual screen to a display.
.Pp
.Fn vcons_redraw_screen
redraws a screen, a driver should call it when returning to terminal emulation mode,
for instance when X exits.
.Pp
.\"
.Vt struct vcons_data
contains all information needed to manage virtual consoles on a display,
usually it will be a member of the driver's softc.
.Pp
.Vt struct vcons_screen
describes a virtual screen.
.Pp
.Sh USAGE
.\"
To use vcons with a driver it needs to be initialized by calling
.Fn vcons_init
, usually in the driver's attach function. 
.Fa vd
should be a pointer to the driver's
.Vt struct vcons_data
.Pp
.Fa cookie
should be a pointer to the driver's softc.
.Pp
.Fa desc
should point to a 
.Vt struct wsscreen_descr
describing the default screen type for this display
.Pp
.Vt accops
points to the driver's 
.Vt struct wsdisplay_accessops
so
.Fn vcons_init
can fill it in with its own implementations of 
.Fn alloc_screen ,
.Fn free_screen
and
.Fn show_screen
.Pp
A driver should however provide its own 
.Fn ioctl
and
.Fn mmap
implementations. Both will receive a pointer to the driver's 
.Vt struct vcons_data
as first parameter.
.Pp
After initialization the driver needs to provide a callback function that
will be called whenever a screen is added, its purpose is to setup the
.Vt struct rasops_info
describing the screen. After that the drawing methods in
.Vt struct rasops_info
will be replaced with wrappers which call the original drawing functions (
which may or may not be provided by the driver ) only when the respective
screen is visible.
To add a virtual screen the driver should call
.Fn vcons_init_screen
which will call the callback function described above, allocate storage for
characters and attributes based on whatever the callback set up in
.Vt struct rasops_info
and add the screen to a list kept in
.Vt struct vcons_data .
.Pp
The callback needs to have this form:
.Pp
.Ft void
.Fn init_screen "void *cookie" "struct vcons_screen *scr" "int existing" \
"long *defattr"
.Pp
and should be stored in the 
.Va init_screen
member found in
.Vt struct vcons_data .
.Fa cookie 
is the cookie passed to 
.Fn vcons_init
.Pp
.Fa scr
points to the 
.Vt struct vcons_screen
being added, its
.Va scr_ri
member, a
.Vt struct rasops_info
needs to be filled in.
.Pp
.Fa existing
is non-zero if the screen already exists and is only added to the list
.Pp
.Fa defattr
points to the screen's default text attribute, it's filled in by
.Fn vcons_init_screen
by calling the 
.Fn alloc_attr
method found in 
.Vt struct rasops_info .
.Pp
When attaching a
.Xr wsdisplay 9
the
.Va accesscookie
member of the
.Vt struct wsemuldisplaydev_attach_args
passed to
.Fn config_found
needs to be a pointer to the driver's
.Vt struct vcons_data .
.Pp
The following members of
.Vt struct vcons_screen 
may be of interest to drivers:
.Pp
.Va scr_ri
contains the 
.Vt struct rasops_info
describing the screen's geometry, access methods and so on
.Pp
.Va scr_cookie
the value passed as cookie to
.Fn vcons_init .
Usually the driver's softc.
.Pp
.Va scr_vd
the driver's
.Vt struct vcons_data .
.Pp
.Va scr_flags
can be zero or any combination of:
.Pp
.Bl -tag -width XXXXXXXXXXXXXXXXXXXXXX -compact
.It Dv VCONS_NO_REDRAW
don't call
.Fn vcons_redraw_screen
when this screen becomes visible.
.It Dv VCONS_SCREEN_IS_STATIC
don't 
.Xr free 9
this screen's
.Vt struct vcons_screen
in
.Fn free_screen
- useful if the screen has been statically allocated.
.El
.Pp
.Va scr_status
currently contains only one flag,
.Dv VCONS_IS_VISIBLE
which is set when the screen is visible.
.Sh SEE ALSO
.Xr wscons 4 ,
.Xr wsdisplay 4