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@xxxxxxxxx>
---
drivers/tty/tty_io.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/tty.h | 3 +++
2 files changed, 53 insertions(+)
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -325,6 +325,56 @@ static struct tty_driver *get_tty_driver
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
/**
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -401,6 +401,7 @@ extern int __init tty_init(void);
extern const char *tty_name(const struct tty_struct *tty);
extern struct tty_struct *tty_open_by_driver(dev_t device, struct inode *inode,
struct file *filp);
+extern int tty_dev_name_to_number(const char *name, dev_t *number);
#else
static inline void tty_kref_put(struct tty_struct *tty)
{ }
@@ -424,6 +425,8 @@ static inline const char *tty_name(const
static inline struct tty_struct *tty_open_by_driver(dev_t device,
struct inode *inode, struct file *filp)
{ return NULL; }
+static inline int tty_dev_name_to_number(const char *name, dev_t *number)
+{ return -ENOTSUPP; }
#endif
extern struct ktermios tty_std_termios;
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