commit be0d5f02c9194fe41c1aad11d7282db117bda938 Author: Kay Sievers <kay....@vrfy.org> Date: Tue Nov 9 18:53:59 2010 +0100

tty: add 'active' sysfs attribute to tty0 and console device

Userspace can query the actual virtual console, and the configured console devices behind /dev/tt0 and /dev/console.

+What: /sys/class/tty/tty0/active +Date: Nov 2010 +Contact: Kay Sievers <kay....@vrfy.org> +Description: + Shows the currently active virtual console + device, like 'tty1'. + The file supports poll() to detect virtual + console switches.

+static ssize_t show_cons_active(struct device *dev, + struct device_attribute *attr, char *buf) +{ + struct console *cs[16]; + int i = 0; + struct console *c; + ssize_t count = 0; + + acquire_console_sem(); + for (c = console_drivers; c; c = c->next) { + if (!c->device) + continue; + if (!c->write) + continue; + if ((c->flags & CON_ENABLED) == 0) + continue; + cs[i++] = c; + if (i >= ARRAY_SIZE(cs)) + break; + } + while (i--) + count += sprintf(buf + count, "%s%d%c", + cs[i]->name, cs[i]->index, i ? ' ':'\n'); + release_console_sem(); + + return count; +} +static DEVICE_ATTR(active, S_IRUGO, show_cons_active, NULL);

- device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 0), NULL, - "tty"); + device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 0), NULL, "tty");

static ATOMIC_NOTIFIER_HEAD(vt_notifier_list); @@ -688,6 +696,8 @@ void redraw_screen(struct vc_data *vc, int is_switch) save_screen(old_vc); set_origin(old_vc); } + if (tty0dev) + sysfs_notify(&tty0dev->kobj, NULL, "active");

+static ssize_t show_tty_active(struct device *dev, + struct device_attribute *attr, char *buf) +{ + return sprintf(buf, "tty%d\n", fg_console + 1); +} +static DEVICE_ATTR(active, S_IRUGO, show_tty_active, NULL);