tty: add function to convert device name to number
The function converts strings like ttyS0 and ttyUSB0 to dev_t like
(4, 64) and (188, 0). It does this by scanning tty_drivers list for
corresponding device name and index. If the driver is not registered,
this function returns -ENODEV. It also acquires tty_mutex.
Signed-off-by: Okash Khawaja <okash.khawaja@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 49abf04..974b13d 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -325,6 +325,56 @@ static struct tty_driver *get_tty_driver(dev_t device, int *index)
return NULL;
}
+/**
+ * tty_dev_name_to_number - return dev_t for device name
+ * @name: user space name of device under /dev
+ * @number: pointer to dev_t that this function will populate
+ *
+ * This function converts device names like ttyS0 or ttyUSB1 into dev_t
+ * like (4, 64) or (188, 1). If no corresponding driver is registered then
+ * the function returns -ENODEV.
+ *
+ * Locking: this acquires tty_mutex to protect the tty_drivers list from
+ * being modified while we are traversing it, and makes sure to
+ * release it before exiting.
+ */
+int tty_dev_name_to_number(const char *name, dev_t *number)
+{
+ struct tty_driver *p;
+ int ret;
+ int index, prefix_length = 0;
+ const char *str;
+
+ for (str = name; *str && !isdigit(*str); str++)
+ ;
+
+ if (!*str)
+ return -EINVAL;
+
+ ret = kstrtoint(str, 10, &index);
+ if (ret)
+ return ret;
+
+ prefix_length = str - name;
+ mutex_lock(&tty_mutex);
+
+ list_for_each_entry(p, &tty_drivers, tty_drivers)
+ if (prefix_length == strlen(p->name) && strncmp(name,
+ p->name, prefix_length) == 0) {
+ if (index < p->num) {
+ *number = MKDEV(p->major, p->minor_start + index);
+ goto out;
+ }
+ }
+
+ /* if here then driver wasn't found */
+ ret = -ENODEV;
+out:
+ mutex_unlock(&tty_mutex);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(tty_dev_name_to_number);
+
#ifdef CONFIG_CONSOLE_POLL
/**
