[PATCH 1/2] tty_io: add an API to get device corresponding to tty_struct

[Dmitry Eremin-Solenikov]

Some device drivers (mostly tty line disciplines) would like to have way
to get a struct device instancve corresponding to passed tty_struct. Add
respective API call.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@xxxxxxxxx>
---
 drivers/char/tty_io.c |   21 +++++++++++++++++++++
 include/linux/tty.h   |    1 +
 2 files changed, 22 insertions(+), 0 deletions(-)

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index d71f0fc..dcdc8fc 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -3017,6 +3017,27 @@ dev_t tty_devnum(struct tty_struct *tty)
 }
 EXPORT_SYMBOL(tty_devnum);
 
+static int dev_match_devt(struct device *dev, void *data)
+{
+	dev_t *devt = data;
+	return dev->devt == *devt;
+}
+
+/**
+ * 	tty_get_device - get a device corresponding to tty
+ * 	@tty: the struct that describes the tty device
+ *
+ * 	Returns a pointer to the struct device for this tty device
+ * 	(or NULL in case of error). Returned device has it's refcount
+ * 	incremented by 1, so you should call put_device() after usage.
+ */
+struct device *tty_get_device(struct tty_struct *tty)
+{
+	dev_t devt = tty_devnum(tty);
+	return class_find_device(tty_class, NULL, &devt, dev_match_devt);
+}
+EXPORT_SYMBOL(tty_get_device);
+
 void proc_clear_tty(struct task_struct *p)
 {
 	unsigned long flags;
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 931078b..5038433 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -451,6 +451,7 @@ extern int tty_mode_ioctl(struct tty_struct *tty, struct file *file,
 			unsigned int cmd, unsigned long arg);
 extern int tty_perform_flush(struct tty_struct *tty, unsigned long arg);
 extern dev_t tty_devnum(struct tty_struct *tty);
+struct device *tty_get_device(struct tty_struct *tty);
 extern void proc_clear_tty(struct task_struct *p);
 extern struct tty_struct *get_current_tty(void);
 extern void tty_default_fops(struct file_operations *fops);
-- 
1.7.1

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