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Commit fbc92a34 authored by Kay Sievers's avatar Kay Sievers Committed by Greg Kroah-Hartman
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tty: add 'active' sysfs attribute to tty0 and console device 



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: default avatarKay Sievers <kay.sievers@vrfy.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>

index 0000000..b138b66
parent 35c64e5d

Documentation/ABI/testing/sysfs-tty

0 → 100644
+19 −0
Original line number Diff line number Diff line 
What:		/sys/class/tty/console/active

Date:		Nov 2010

Contact:	Kay Sievers <kay.sievers@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.sievers@vrfy.org>

Description:

		 Shows the currently active virtual console

		 device, like 'tty1'.

		 The file supports poll() to detect virtual

		 console switches.

drivers/tty/tty_io.c

+43 −4
Original line number Diff line number Diff line
@@ -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);

drivers/tty/vt/vt.c

+22 −1
Original line number Diff line number Diff line
@@ -235,6 +235,14 @@ enum { 
	blank_vesa_wait,

};



/*

 * /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.

 */
@@ -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();

include/linux/console.h

+1 −1
Original line number Diff line number Diff line
@@ -151,7 +151,7 @@ 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 */

kernel/printk.c

+2 −0
Original line number Diff line number Diff line
@@ -1332,6 +1332,7 @@ 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
@@ -1390,6 +1391,7 @@ int unregister_console(struct console *console) 
		console_drivers->flags |= CON_CONSDEV;



	release_console_sem();

	console_sysfs_notify();

	return res;

}

EXPORT_SYMBOL(unregister_console);