vcons(9) - NetBSD Manual Pages

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VCONS(9)               NetBSD 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 con- soles 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() implementa- tions. 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 orig- inal 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 mem- ber, 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 driv- ers: 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 stat- ically 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) NetBSD 9.99 February 12, 2006 NetBSD 9.99
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