VCONS(9)						   BSD Kernel Developer's Manual						  VCONS(9)

NAME

     vcons -- generic virtual console framework

SYNOPSIS

     #include <wscons/wsdisplay_vconsvar.h>

     int
     vcons_init(struct vcons_data *vd, void *cookie, struct wsscreen_descr *desc, struct wsdisplay_accessops *accops);

     int
     vcons_init_screen(struct vcons_data *vd, struct vcons_screen *scr, int exists, long *defattr);

     void
     vcons_redraw_screen(struct vcons_screen *scr);

DESCRIPTION

     These functions are used to setup and control the generic virtual console framework.

     The vcons_init() function initializes the framework, it needs to be called for each driver that's going to use vcons.

     vcons_init_screen() adds a virtual screen to a display.

     vcons_redraw_screen() redraws a screen.  A driver should call it when returning to terminal emulation mode, for instance when X exits.

     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.

     struct vcons_screen describes a virtual screen.

USAGE

     To use vcons with a driver it needs to be initialized by calling vcons_init(), usually in the driver's attach function.

     vd        should be a pointer to the driver's struct vcons_data.

     cookie    should be a pointer to the driver's softc.

     desc      should point to a struct wsscreen_descr describing the default screen type for this display.

     accops    points to the driver's struct wsdisplay_accessops so vcons_init() can fill it in with its own implementations of alloc_screen(),
	       free_screen(), and show_screen().

     A driver should however provide its own ioctl() and mmap() implementations.  Both will receive a pointer to the driver's struct vcons_data as
     first parameter.

     After initialization the driver needs to provide a callback function that will be called whenever a screen is added.  Its purpose is to set
     up the struct rasops_info describing the screen.  After that the drawing methods in 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 one should call 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 struct rasops_info, and add the screen to a list kept in struct
     vcons_data.

     The callback needs to have this form:

     void init_screen(void *cookie, struct vcons_screen *scr, int existing, long *defattr)

     and should be stored in the init_screen member found in struct vcons_data.  The arguments are:

     cookie    is the cookie passed to vcons_init()

     scr       points to the struct vcons_screen being added, its scr_ri member, a struct rasops_info, needs to be filled in.

     existing  is non-zero if the screen already exists and is only added to the list.

     defattr   points to the screen's default text attribute.  It's filled in by vcons_init_screen() by calling the alloc_attr() method found in
	       struct rasops_info.

     When attaching a wsdisplay(9) the accesscookie member of the struct wsemuldisplaydev_attach_args passed to config_found() needs to be a
     pointer to the driver's struct vcons_data.

     The following members of struct vcons_screen may be of interest to drivers:

     scr_ri	   contains the struct rasops_info describing the screen's geometry, access methods and so on.

     scr_cookie    the value passed as cookie to vcons_init().	Usually the driver's softc.

     scr_vd	   the driver's struct vcons_data.

     scr_flags	   can be zero or any combination of:
		   VCONS_NO_REDRAW	   don't call vcons_redraw_screen() when this screen becomes visible.
		   VCONS_SCREEN_IS_STATIC  don't free(9) this screen's struct vcons_screen in free_screen() - useful if the screen has been stati-
					   cally allocated.

     scr_status    currently contains only one flag, VCONS_IS_VISIBLE, which is set when the screen is visible.

SEE ALSO

     wscons(4), wsdisplay(4)

BSD
								 February 12, 2006							       BSD