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Support VT switching for fbdev backend #89

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Merged
merged 1 commit into from
Jan 21, 2025
Merged

Support VT switching for fbdev backend #89

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71 changes: 53 additions & 18 deletions backend/fbdev.c
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,8 @@ typedef struct {

/* Linux virtual terminal (VT) */
int vt_fd;
bool vt_active;
struct vt_mode old_vtm;

/* Linux framebuffer */
int fb_fd;
Expand Down Expand Up @@ -86,22 +88,6 @@ static void twin_fbdev_get_screen_size(twin_fbdev_t *tx,
*height = info.yres;
}

static void twin_fbdev_damage(twin_screen_t *screen, twin_fbdev_t *tx)
{
int width, height;
twin_fbdev_get_screen_size(tx, &width, &height);
twin_screen_damage(tx->screen, 0, 0, width, height);
}

static bool twin_fbdev_work(void *closure)
{
twin_screen_t *screen = SCREEN(closure);

if (twin_screen_damaged(screen))
twin_screen_update(screen);
return true;
}

static inline bool twin_fbdev_is_rgb565(twin_fbdev_t *tx)
{
return tx->fb_var.red.offset == 11 && tx->fb_var.red.length == 5 &&
Expand Down Expand Up @@ -192,6 +178,50 @@ static bool twin_fbdev_apply_config(twin_fbdev_t *tx)
return true;
}

static void twin_fbdev_damage(twin_fbdev_t *tx)
{
int width, height;
twin_fbdev_get_screen_size(tx, &width, &height);
twin_screen_damage(tx->screen, 0, 0, width, height);
}

static bool twin_fbdev_update_damage(void *closure)
{
twin_fbdev_t *tx = PRIV(closure);
twin_screen_t *screen = SCREEN(closure);

if (!tx->vt_active && twin_screen_damaged(screen))
twin_screen_update(screen);

return true;
}

static bool twin_fbdev_work(void *closure)
{
twin_fbdev_t *tx = PRIV(closure);
twin_screen_t *screen = SCREEN(closure);

if (tx->vt_active && (tx->fb_base != MAP_FAILED)) {
/* Unmap the fbdev */
munmap(tx->fb_base, tx->fb_len);
tx->fb_base = MAP_FAILED;
}

if (!tx->vt_active && (tx->fb_base == MAP_FAILED)) {
/* Restore the fbdev settings */
if (!twin_fbdev_apply_config(tx))
log_error("Failed to apply configurations to the fbdev");

/* Mark entire screen for refresh */
twin_screen_damage(screen, 0, 0, screen->width, screen->height);
}

if (!tx->vt_active && twin_screen_damaged(screen))
twin_screen_update(screen);

return true;
}

twin_context_t *twin_fbdev_init(int width, int height)
{
char *fbdev_path = getenv(FBDEV_NAME);
Expand All @@ -218,10 +248,13 @@ twin_context_t *twin_fbdev_init(int width, int height)
}

/* Set up virtual terminal environment */
if (!twin_vt_setup(&tx->vt_fd)) {
if (!twin_vt_setup(&tx->vt_fd, &tx->old_vtm, &tx->vt_active)) {
goto bail_fb_fd;
}

/* Set up signal handlers for switching TTYs */
twin_vt_setup_signal_handler();

/* Apply configurations to the framebuffer device */
if (!twin_fbdev_apply_config(tx)) {
log_error("Failed to apply configurations to the framebuffer device");
Expand Down Expand Up @@ -254,6 +287,9 @@ twin_context_t *twin_fbdev_init(int width, int height)
/* Setup file handler and work functions */
twin_set_work(twin_fbdev_work, TWIN_WORK_REDISPLAY, ctx);

/* Register a callback function to handle damaged rendering */
twin_screen_register_damaged(ctx->screen, twin_fbdev_update_damage, ctx);

return ctx;

bail_screen:
Expand Down Expand Up @@ -292,7 +328,6 @@ static void twin_fbdev_exit(twin_context_t *ctx)
}

/* Register the Linux framebuffer backend */

const twin_backend_t g_twin_backend = {
.init = twin_fbdev_init,
.configure = twin_fbdev_configure,
Expand Down
78 changes: 76 additions & 2 deletions backend/linux_vt.h
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Original file line number Diff line number Diff line change
Expand Up @@ -10,11 +10,19 @@
#include <fcntl.h>
#include <linux/kd.h>
#include <linux/vt.h>
#include <signal.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include "twin_private.h"

#define VT_DEV_TTY_MAX 11
#define SIG_SWITCH_FROM SIGUSR1
#define SIG_SWITCH_TO SIGUSR2

static volatile sig_atomic_t *vt_fd;

static volatile sig_atomic_t *is_vt_actived;

static inline int twin_vt_open(int vt_num)
{
int fd;
Expand All @@ -35,7 +43,42 @@ static inline int twin_vt_mode(int fd, int mode)
return ioctl(fd, KDSETMODE, mode);
}

static inline bool twin_vt_setup(int *fd_ptr)
static void twin_vt_process_switch_signal(int signum)
{
if (signum == SIG_SWITCH_FROM) {
/* Notify kernel to release current virtual terminal */
ioctl(*vt_fd, VT_RELDISP, 1);

/* Set the virtual terminal display in text mode */
ioctl(*vt_fd, KDSETMODE, KD_TEXT);

*is_vt_actived = true;
} else if (signum == SIG_SWITCH_TO) {
/* Switch complete */
ioctl(*vt_fd, VT_RELDISP, VT_ACKACQ);

/* Restore the virtual terminal display in graphics mode */
ioctl(*vt_fd, KDSETMODE, KD_GRAPHICS);

*is_vt_actived = false;
}
}

static inline void twin_vt_setup_signal_handler()
{
struct sigaction tty_sig = {.sa_handler = twin_vt_process_switch_signal};
sigfillset(&tty_sig.sa_mask);

/* Set the signal handler for leaving the current TTY */
sigaction(SIG_SWITCH_FROM, &tty_sig, NULL);

/* Set the signal handler for returning to the previous TTY */
sigaction(SIG_SWITCH_TO, &tty_sig, NULL);
}

static inline bool twin_vt_setup(int *fd_ptr,
struct vt_mode *old_vtm,
bool *vt_active)
{
/* Open VT0 to inquire information */
if ((*fd_ptr = twin_vt_open(0)) < -1) {
Expand All @@ -57,12 +100,43 @@ static inline bool twin_vt_setup(int *fd_ptr)
return false;
}

/* Set VT to graphics mode to inhibit command-line text */
/* Attempt to activate the specified virtual terminal by its number */
if (ioctl(*fd_ptr, VT_ACTIVATE, vt_num) < 0) {
log_error("Failed to activate VT %d", vt_num);
return false;
}

/* Wait until the specified virtual terminal becomes the active VT */
if (ioctl(*fd_ptr, VT_WAITACTIVE, vt_num) < 0) {
log_error("Failed to activate VT %d", vt_num);
return false;
}

/* Save the virtual terminal mode */
if (ioctl(*fd_ptr, VT_GETMODE, &old_vtm) < 0) {
log_error("Failed to get VT mode");
return false;
}

/* Set the virtual terminal mode */
struct vt_mode vtm = {
.mode = VT_PROCESS, .relsig = SIGUSR1, .acqsig = SIGUSR2};

if (ioctl(*fd_ptr, VT_SETMODE, &vtm) < 0) {
log_error("Failed to set VT mode");
return false;
}

/* Set the virtual terminal display mode to graphics mode */
if (twin_vt_mode(*fd_ptr, KD_GRAPHICS) < 0) {
log_error("Failed to set KD_GRAPHICS mode");
twin_vt_mode(*fd_ptr, KD_TEXT);
return false;
}

vt_fd = fd_ptr;
is_vt_actived = vt_active;

return true;
}
#endif