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.

The last entry in the list of devices is the active device, analog to the console= kernel command line option.

The attribute supports poll(), which is raised when the virtual console is changed or /dev/console is reconfigured.

Signed-off-by: Kay Sievers <kay....@vrfy.org>

diff --git a/Documentation/ABI/testing/sysfs-tty
b/Documentation/ABI/testing/sysfs-tty new file mode 100644 index 0000000..b138b66 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-tty @@ -0,0 +1,19 @@ +What: /sys/class/tty/console/active +Date: Nov 2010 +Contact: Kay Sievers <kay....@vrfy.org> +Description: + Shows the list of currently configured + console devices, like 'tty1 ttyS0'. + The last entry in the file is the active + device connected to /dev/console. + The file supports poll() to detect virtual + console switches. + +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. diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index c05c5af..be5ab4a 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -3232,9 +3232,45 @@ static int __init tty_class_init(void) postcore_initcall(tty_class_init);

/* 3/2004 jmc: why do these devices exist? */ - static struct cdev tty_cdev, console_cdev;

+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); + +static struct device *consdev; + +void console_sysfs_notify(void) +{ + if (consdev) + sysfs_notify(&consdev->kobj, NULL, "active"); +} + /* * Ok, now we can initialize the rest of the tty devices and can count * on memory allocations, interrupts etc.. @@ -3245,15 +3281,18 @@ int __init tty_init(void) if (cdev_add(&tty_cdev, MKDEV(TTYAUX_MAJOR, 0), 1) || register_chrdev_region(MKDEV(TTYAUX_MAJOR, 0), 1, "/dev/tty") < 0) panic("Couldn't register /dev/tty driver\n"); - device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 0), NULL, - "tty"); + device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 0), NULL, "tty");

cdev_init(&console_cdev, &console_fops); if (cdev_add(&console_cdev, MKDEV(TTYAUX_MAJOR, 1), 1) || register_chrdev_region(MKDEV(TTYAUX_MAJOR, 1), 1, "/dev/console") < 0) panic("Couldn't register /dev/console driver\n"); - device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 1), NULL, + consdev = device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 1), NULL, "console"); + if (IS_ERR(consdev)) + consdev = NULL; + else + device_create_file(consdev, &dev_attr_active);

#ifdef CONFIG_VT vty_init(&console_fops); diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index a8ec48e..76407ec 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -236,6 +236,14 @@ enum { };

/* + * /sys/class/tty/tty0/ + * + * the attribute 'active' contains the name of the current vc + * console and it supports poll() to detect vc switches + */ +static struct device *tty0dev; + +/* * Notifier list for console events. */ 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"); } else { hide_cursor(vc); redraw = 1; @@ -2967,13 +2977,24 @@ static const struct tty_operations con_ops = {

static struct cdev vc0_cdev;

+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); + int __init vty_init(const struct file_operations *console_fops) { cdev_init(&vc0_cdev, console_fops); if (cdev_add(&vc0_cdev, MKDEV(TTY_MAJOR, 0), 1) || register_chrdev_region(MKDEV(TTY_MAJOR, 0), 1, "/dev/vc/0") < 0) panic("Couldn't register /dev/tty0 driver\n"); - device_create(tty_class, NULL, MKDEV(TTY_MAJOR, 0), NULL, "tty0"); + tty0dev = device_create(tty_class, NULL, MKDEV(TTY_MAJOR, 0), NULL, "tty0"); + if (IS_ERR(tty0dev)) + tty0dev = NULL; + else + device_create_file(tty0dev, &dev_attr_active);

vcs_init();

diff --git a/include/linux/console.h b/include/linux/console.h index 95cf6f0..0752d92 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -145,7 +145,7 @@ extern int is_console_locked(void); extern int braille_register_console(struct console *, int index, char *console_options, char *braille_options); extern int braille_unregister_console(struct console *); - +extern void console_sysfs_notify(void); extern int console_suspend_enabled;

/* Suspend and resume console messages over PM events */ diff --git a/kernel/printk.c b/kernel/printk.c index 9a2264f..16f2084 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -1357,6 +1357,7 @@ void register_console(struct console *newcon) spin_unlock_irqrestore(&logbuf_lock, flags); } release_console_sem(); + console_sysfs_notify();

/* * By unregistering the bootconsoles after we enable the real console @@ -1415,6 +1416,7 @@ int unregister_console(struct console *console) console_drivers->flags |= CON_CONSDEV;

release_console_sem(); + console_sysfs_notify(); return res; } EXPORT_SYMBOL(unregister_console);