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Date: Tue, 7 Sep 2010 18:53:05 +0200
From: "Dr. Werner Fink" <werner@...e.de>
To: Greg KH <gregkh@...e.de>
Cc: Alan Cox <alan@...rguk.ukuu.org.uk>, linux-kernel@...r.kernel.org,
linux-api@...r.kernel.org
Subject: [PATCH] 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.
Signed-off-by: Werner Fink <werner@...e.de>
---
Documentation/filesystems/proc.txt | 16 ++++
fs/proc/proc_tty.c | 138 ++++++++++++++++++++++++++++++++++++
2 files changed, 154 insertions(+), 0 deletions(-)
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index 9fb6cbe..a5b6dd5 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -1074,6 +1074,7 @@ 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
@@ -1092,6 +1093,21 @@ 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 4:7
+ ttyS0 4:64
+
+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 4:7
+ > tty
+ /dev/pts/3
+
1.8 Miscellaneous kernel statistics in /proc/stat
-------------------------------------------------
diff --git a/fs/proc/proc_tty.c b/fs/proc/proc_tty.c
index 83adcc8..f717e84 100644
--- a/fs/proc/proc_tty.c
+++ b/fs/proc/proc_tty.c
@@ -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>
/*
@@ -137,6 +140,140 @@ static const struct file_operations proc_tty_drivers_operations = {
};
/*
+ * 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;
+ 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;
+
+ seq_printf(m, "%s%s%d%n", (current_dev == dev) ? "*" : "",
+ con->name, con->index, &len);
+ len = 19 - len;
+ if (len < 1)
+ len = 1;
+ seq_printf(m, "%*c%d:%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 (!con->write)
+ continue;
+ if ((con->flags & CON_ENABLED) == 0)
+ 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;
+ if (!con->write)
+ continue;
+ if ((con->flags & CON_ENABLED) == 0)
+ 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
+};
+
+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 +323,5 @@ 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);
}
--
1.6.0.2
--
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