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Subject[PATCH, RFC, BAD IDEA] /proc/tty/console
I'm not seriously proposing this. But, as far as I can tell, this
information isn't exposed to userspace anywhere, and it's a useful
thing to know. I'm certainly open for better ideas on how to expose
this (sysfs attributes? other?)

....

The attached patch adds /proc/tty/console. The contents of it are
simply a description of the current drivers attached to /dev/console.
For example, a boot with 'console=ttyS3,115200n1 console=tty0' would
yield:

# cat /proc/tty/console
unknown /dev/tty0
serial /dev/ttyS3

Bill

---
diff -ru linux-2.6.24.noarch/fs/proc/proc_tty.c linux/fs/proc/proc_tty.c
--- linux-2.6.24.noarch/fs/proc/proc_tty.c 2008-02-27 12:50:59.000000000 -0500
+++ linux/fs/proc/proc_tty.c 2008-02-27 12:25:54.000000000 -0500
@@ -6,6 +6,7 @@

#include <asm/uaccess.h>

+#include <linux/console.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/time.h>
@@ -129,6 +130,38 @@
return seq_open(file, &tty_drivers_op);
}

+static int show_tty_console(struct seq_file *m, void *v)
+{
+ int index;
+ struct console *c;
+
+ for (c = console_drivers; c ; c = c->next) {
+ struct tty_driver *t = NULL;
+ if (!c->device)
+ continue;
+ t = c->device(c, &index);
+ seq_printf(m, "%-20s", t->driver_name ? t->driver_name : "unknown");
+ seq_printf(m, "/dev/%s%d", t->name, c->index);
+ seq_printf(m, "\n");
+ }
+ return 0;
+}
+
+static void *c_start(struct seq_file *m, loff_t *pos)
+{
+ return *pos == 0 ? &c_start : NULL;
+}
+
+static void *c_next(struct seq_file *m, void *v, loff_t *pos)
+{
+ ++*pos;
+ return c_start(m, pos);
+}
+
+static void c_stop(struct seq_file *m, void *v)
+{
+}
+
static const struct file_operations proc_tty_drivers_operations = {
.open = tty_drivers_open,
.read = seq_read,
@@ -136,6 +169,25 @@
.release = seq_release,
};

+static const struct seq_operations tty_console_op = {
+ .start = c_start,
+ .next = c_next,
+ .stop = c_stop,
+ .show = show_tty_console
+};
+
+static int tty_console_open(struct inode *inode, struct file *file)
+{
+ return seq_open(file, &tty_console_op);
+}
+
+static const struct file_operations proc_tty_console_operations = {
+ .open = tty_console_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release
+};
+
/*
* This is the handler for /proc/tty/ldiscs
*/
@@ -230,4 +282,7 @@
entry = create_proc_entry("tty/drivers", 0, NULL);
if (entry)
entry->proc_fops = &proc_tty_drivers_operations;
+ entry = create_proc_entry("tty/console", 0, NULL);
+ if (entry)
+ entry->proc_fops = &proc_tty_console_operations;
}

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