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

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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.sievers@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

index 0000000..b138b66
This commit is contained in:
Kay Sievers 2010-12-01 18:51:05 +01:00 committed by Greg Kroah-Hartman
parent 35c64e5d13
commit fbc92a3455
5 changed files with 87 additions and 6 deletions
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19
Documentation/ABI/testing/sysfs-tty Normal file
View File

@ -0,0 +1,19 @@
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.

47
drivers/tty/tty_io.c
View File

@ -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);

23
drivers/tty/vt/vt.c
View File

@ -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();

2
include/linux/console.h
View File

@ -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 */

2
kernel/printk.c
View File

@ -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);