3 files changed, 139 insertions, 0 deletions

diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index e73df2722ff3..9471225212c4 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -1181,6 +1181,30 @@ Table 1-12: Files in /proc/fs/ext4/<devname>
  mb_groups       details of multiblock allocator buddy cache of free blocks
 ..............................................................................
 
+2.0 /proc/consoles
+------------------
+Shows registered system console lines.
+
+To see which character device lines are currently used for the system console
+/dev/console, you may simply look into the file /proc/consoles:
+
+  > cat /proc/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
+  major:minor          major and minor number of the device separated by a colon
 
 ------------------------------------------------------------------------------
 Summary
diff --git a/fs/proc/Makefile b/fs/proc/Makefile
index 2758e2afc518..288a49e098bf 100644
--- a/fs/proc/Makefile
+++ b/fs/proc/Makefile
@@ -15,6 +15,7 @@ proc-y	+= devices.o
 proc-y  += interrupts.o
 proc-y  += loadavg.o
 proc-y  += meminfo.o
+proc-y  += proc_console.o
 proc-y  += stat.o
 proc-y  += uptime.o
 proc-y  += version.o
diff --git a/fs/proc/proc_console.c b/fs/proc/proc_console.c
new file mode 100644
index 000000000000..8a707609f528
--- /dev/null
+++ b/fs/proc/proc_console.c
@@ -0,0 +1,114 @@
+/*
+ * Copyright (c) 2010 Werner Fink, Jiri Slaby
+ *
+ * Licensed under GPLv2
+ */
+
+#include <linux/console.h>
+#include <linux/kernel.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/tty_driver.h>
+
+/*
+ * This is handler for /proc/consoles
+ */
+static int show_console_dev(struct seq_file *m, void *v)
+{
+        static const struct {
+                short flag;
+                char name;
+        } con_flags[] = {
+                { CON_ENABLED,          'E' },
+                { CON_CONSDEV,          'C' },
+                { CON_BOOT,             'B' },
+                { CON_PRINTBUFFER,      'p' },
+                { CON_BRL,              'b' },
+                { CON_ANYTIME,          'a' },
+        };
+        char flags[ARRAY_SIZE(con_flags) + 1];
+        struct console *con = v;
+        unsigned int a;
+        int len;
+        dev_t dev = 0;
+
+        if (con->device) {
+                const struct tty_driver *driver;
+                int index;
+                driver = con->device(con, &index);
+                if (driver) {
+                        dev = MKDEV(driver->major, driver->minor_start);
+                        dev += index;
+                }
+        }
+
+        for (a = 0; a < ARRAY_SIZE(con_flags); a++)
+                flags[a] = (con->flags & con_flags[a].flag) ?
+                        con_flags[a].name : ' ';
+        flags[a] = 0;
+
+        seq_printf(m, "%s%d%n", con->name, con->index, &len);
+        len = 21 - len;
+        if (len < 1)
+                len = 1;
+        seq_printf(m, "%*c%c%c%c (%s)", len, ' ', con->read ? 'R' : '-',
+                        con->write ? 'W' : '-', con->unblank ? 'U' : '-',
+                        flags);
+        if (dev)
+                seq_printf(m, " %4d:%d", MAJOR(dev), MINOR(dev));
+
+        seq_printf(m, "\n");
+
+        return 0;
+}
+
+static void *c_start(struct seq_file *m, loff_t *pos)
+{
+        struct console *con;
+        loff_t off = 0;
+
+        acquire_console_sem();
+        for_each_console(con)
+                if (off++ == *pos)
+                        break;
+
+        return con;
+}
+
+static void *c_next(struct seq_file *m, void *v, loff_t *pos)
+{
+        struct console *con = v;
+        ++*pos;
+        return con->next;
+}
+
+static void c_stop(struct seq_file *m, void *v)
+{
+        release_console_sem();
+}
+
+static const struct seq_operations consoles_op = {
+        .start  = c_start,
+        .next   = c_next,
+        .stop   = c_stop,
+        .show   = show_console_dev
+};
+
+static int consoles_open(struct inode *inode, struct file *file)
+{
+        return seq_open(file, &consoles_op);
+}
+
+static const struct file_operations proc_consoles_operations = {
+        .open           = consoles_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = seq_release,
+};
+
+static int register_proc_consoles(void)
+{
+        proc_create("consoles", 0, NULL, &proc_consoles_operations);
+        return 0;
+}
+module_init(register_proc_consoles);