tty: Add a new file /proc/tty/consoles

Add a new file /proc/tty/consoles to be able to determine the registered
system console lines.  If the reading process holds /dev/console open at
the regular standard input stream the active device will be marked by an
asterisk.  Show possible operations and also decode the used flags of
the listed console lines.

Signed-off-by: Werner Fink <werner@suse.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Dr. Werner Fink 2010-09-22 12:45:40 +02:00 committed by Greg Kroah-Hartman
parent a9e2e06015
commit f4a3e0bceb
2 changed files with 190 additions and 0 deletions

View File

@ -1075,6 +1075,7 @@ Table 1-11: Files in /proc/tty
drivers list of drivers and their usage
ldiscs registered line disciplines
driver/serial usage statistic and status of single tty lines
consoles registered system console lines
..............................................................................
To see which tty's are currently in use, you can simply look into the file
@ -1093,6 +1094,37 @@ To see which tty's are currently in use, you can simply look into the file
/dev/tty /dev/tty 5 0 system:/dev/tty
unknown /dev/tty 4 1-63 console
To see which character device lines are currently used for the system console
/dev/console, you may simply look into the file /proc/tty/consoles:
> cat /proc/tty/consoles
tty0 -WU (ECp) 4:7
ttyS0 -W- (Ep) 4:64
The columns are:
device name of the device
operations R = can do read operations
W = can do write operations
U = can do unblank
flags E = it is enabled
C = it is prefered console
B = it is primary boot console
p = it is used for printk buffer
b = it is not a TTY but a Braille device
a = it is safe to use when cpu is offline
* = it is standard input of the reading process
major:minor major and minor number of the device separated by a colon
If the reading process holds /dev/console open at the regular standard input
stream the active device will be marked by an asterisk:
> cat /proc/tty/consoles < /dev/console
tty0 -WU (ECp*) 4:7
ttyS0 -W- (Ep) 4:64
> tty
/dev/pts/3
1.8 Miscellaneous kernel statistics in /proc/stat
-------------------------------------------------

View File

@ -12,7 +12,10 @@
#include <linux/proc_fs.h>
#include <linux/stat.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/console.h>
#include <linux/seq_file.h>
#include <linux/fdtable.h>
#include <linux/bitops.h>
/*
@ -136,6 +139,160 @@ static const struct file_operations proc_tty_drivers_operations = {
.release = seq_release,
};
/*
* The device ID of file descriptor 0 of the current reading
* task if a character device...
*/
static dev_t current_dev;
/*
* This is the handler for /proc/tty/consoles
*/
static int show_console_dev(struct seq_file *m, void *v)
{
const struct tty_driver *driver;
struct console *con;
int index, len;
char flags[10];
dev_t dev;
if (v == SEQ_START_TOKEN)
return 0;
con = (struct console *)v;
if (!con)
return 0;
driver = con->device(con, &index);
if (!driver)
return 0;
dev = MKDEV(driver->major, driver->minor_start) + index;
index = 0;
if (con->flags & CON_ENABLED)
flags[index++] = 'E';
if (con->flags & CON_CONSDEV)
flags[index++] = 'C';
if (con->flags & CON_BOOT)
flags[index++] = 'B';
if (con->flags & CON_PRINTBUFFER)
flags[index++] = 'p';
if (con->flags & CON_BRL)
flags[index++] = 'b';
if (con->flags & CON_ANYTIME)
flags[index++] = 'a';
if (current_dev == dev)
flags[index++] = '*';
flags[index] = 0;
seq_printf(m, "%s%d%n", con->name, con->index, &len);
len = 21 - len;
if (len < 1)
len = 1;
seq_printf(m, "%*c", len, ' ');
seq_printf(m, "%c%c%c (%s)%n", con->read ? 'R' : '-',
con->write ? 'W' : '-', con->unblank ? 'U' : '-',
flags, &len);
len = 13 - len;
if (len < 1)
len = 1;
seq_printf(m, "%*c%4d:%d\n", len, ' ', MAJOR(dev), MINOR(dev));
return 0;
}
/* iterator for consoles */
static void *c_start(struct seq_file *m, loff_t *pos)
{
struct console *con;
loff_t off = 0;
if (*pos == 0)
return SEQ_START_TOKEN;
acquire_console_sem();
for (con = console_drivers; con; con = con->next) {
if (!con->device)
continue;
if (++off == *pos)
break;
}
release_console_sem();
return con;
}
static void *c_next(struct seq_file *m, void *v, loff_t *pos)
{
struct console *con;
acquire_console_sem();
if (v == SEQ_START_TOKEN)
con = console_drivers;
else
con = ((struct console *)v)->next;
for (; con; con = con->next) {
if (!con->device)
continue;
++*pos;
break;
}
release_console_sem();
return con;
}
static void c_stop(struct seq_file *m, void *v)
{
}
static const struct seq_operations tty_consoles_op = {
.start = c_start,
.next = c_next,
.stop = c_stop,
.show = show_console_dev
};
/*
* Used for open /proc/tty/consoles. Before this detect
* the device ID of file descriptor 0 of the current
* reading task if a character device...
*/
static int tty_consoles_open(struct inode *inode, struct file *file)
{
struct files_struct *curfiles;
current_dev = 0;
curfiles = get_files_struct(current);
if (curfiles) {
const struct file *curfp;
spin_lock(&curfiles->file_lock);
curfp = fcheck_files(curfiles, 0);
if (curfp && curfp->private_data) {
const struct inode *inode;
dget(curfp->f_dentry);
inode = curfp->f_dentry->d_inode;
if (S_ISCHR(inode->i_mode)) {
struct tty_struct *tty;
tty = (struct tty_struct *)curfp->private_data;
if (tty && tty->magic == TTY_MAGIC) {
tty = tty_pair_get_tty(tty);
current_dev = tty_devnum(tty);
}
}
dput(curfp->f_dentry);
}
spin_unlock(&curfiles->file_lock);
put_files_struct(curfiles);
}
return seq_open(file, &tty_consoles_op);
}
static const struct file_operations proc_tty_consoles_operations = {
.open = tty_consoles_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release,
};
/*
* This function is called by tty_register_driver() to handle
* registering the driver's /proc handler into /proc/tty/driver/<foo>
@ -186,4 +343,5 @@ void __init proc_tty_init(void)
proc_tty_driver = proc_mkdir_mode("tty/driver", S_IRUSR|S_IXUSR, NULL);
proc_create("tty/ldiscs", 0, NULL, &tty_ldiscs_proc_fops);
proc_create("tty/drivers", 0, NULL, &proc_tty_drivers_operations);
proc_create("tty/consoles", 0, NULL, &proc_tty_consoles_operations);
}