VCONS(9)

💖 NAME 💖

okay so bestie, meet vcons — the generic virtual console framework. This is the VCONS(9) page from the Kernel Developer's Manual, and it's here to explain the setup-and-control functions for virtual consoles. periodt 💅

🎀 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. No cap, that's the whole vibe.

• vcons_init() — initializes the framework; it needs to be called for each driver that's going to use vcons. It's the main-character init moment ✨.
• vcons_init_screen() — adds a virtual screen to a display. slay.
• vcons_redraw_screen() — redraws a screen. A driver should call it when returning to terminal emulation mode, for instance when X exits. iykyk.

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. Here are the args, bestie:

• 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. no cap, that first param matters.

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. It's giving invisible-screen protection 💅.

To add a virtual screen the driver 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. obsessed with the organization.

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. Don't forget this, bestie.

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 statically 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)

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mwah 💋 — source/version: Debian, date: February 12, 2006. byeee bestie, go be iconic with your virtual consoles 🫶💖