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Subject[PATCH v4 1/3] tty: rename tty_kopen() and add new function tty_kopen_shared()
Date
Introduce a new function tty_kopen_shared() that yields a struct
tty_struct. The semantic difference to tty_kopen() is that the tty is
expected to be used already. So rename tty_kopen() to
tty_kopen_exclusive() for clearness, adapt the single user and put the
common code in a new static helper function.

tty_kopen_shared is to be used to implement an LED trigger for tty
devices in one of the next patches.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
drivers/staging/speakup/spk_ttyio.c | 2 +-
drivers/tty/tty_io.c | 58 ++++++++++++++++++++---------
include/linux/tty.h | 5 ++-
3 files changed, 44 insertions(+), 21 deletions(-)

diff --git a/drivers/staging/speakup/spk_ttyio.c b/drivers/staging/speakup/spk_ttyio.c
index 5a9eff08cb96..e9db06eae875 100644
--- a/drivers/staging/speakup/spk_ttyio.c
+++ b/drivers/staging/speakup/spk_ttyio.c
@@ -147,7 +147,7 @@ static int spk_ttyio_initialise_ldisc(struct spk_synth *synth)
if (ret)
return ret;

- tty = tty_kopen(dev);
+ tty = tty_kopen_exclusive(dev);
if (IS_ERR(tty))
return PTR_ERR(tty);

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index a1453fe10862..b718666ce73c 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -1875,22 +1875,7 @@ static struct tty_driver *tty_lookup_driver(dev_t device, struct file *filp,
return driver;
}

-/**
- * tty_kopen - open a tty device for kernel
- * @device: dev_t of device to open
- *
- * Opens tty exclusively for kernel. Performs the driver lookup,
- * makes sure it's not already opened and performs the first-time
- * tty initialization.
- *
- * Returns the locked initialized &tty_struct
- *
- * Claims the global tty_mutex to serialize:
- * - concurrent first-time tty initialization
- * - concurrent tty driver removal w/ lookup
- * - concurrent tty removal from driver table
- */
-struct tty_struct *tty_kopen(dev_t device)
+static struct tty_struct *tty_kopen(dev_t device, int shared)
{
struct tty_struct *tty;
struct tty_driver *driver;
@@ -1905,7 +1890,7 @@ struct tty_struct *tty_kopen(dev_t device)

/* check whether we're reopening an existing tty */
tty = tty_driver_lookup_tty(driver, NULL, index);
- if (IS_ERR(tty))
+ if (IS_ERR(tty) || shared)
goto out;

if (tty) {
@@ -1923,7 +1908,44 @@ struct tty_struct *tty_kopen(dev_t device)
tty_driver_kref_put(driver);
return tty;
}
-EXPORT_SYMBOL_GPL(tty_kopen);
+
+/**
+ * tty_kopen_exclusive - open a tty device for kernel
+ * @device: dev_t of device to open
+ *
+ * Opens tty exclusively for kernel. Performs the driver lookup,
+ * makes sure it's not already opened and performs the first-time
+ * tty initialization.
+ *
+ * Returns the locked initialized &tty_struct
+ *
+ * Claims the global tty_mutex to serialize:
+ * - concurrent first-time tty initialization
+ * - concurrent tty driver removal w/ lookup
+ * - concurrent tty removal from driver table
+ */
+struct tty_struct *tty_kopen_exclusive(dev_t device)
+{
+ return tty_kopen(device, 0);
+}
+EXPORT_SYMBOL_GPL(tty_kopen_exclusive);
+
+/**
+ * tty_kopen_shared - open a tty device for shared in-kernel use
+ * @device: dev_t of device to open
+ *
+ * Opens an already existing tty
+ * rnel. Performs the driver lookup,
+ * makes sure it's not already opened and performs the first-time
+ * tty initialization.
+ *
+ * Locking is identical to tty_kopen() above.
+ */
+struct tty_struct *tty_kopen_shared(dev_t device)
+{
+ return tty_kopen(device, 1);
+}
+EXPORT_SYMBOL_GPL(tty_kopen_shared);

/**
* tty_open_by_driver - open a tty device
diff --git a/include/linux/tty.h b/include/linux/tty.h
index bfa4e2ee94a9..d0bcf3226fb2 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -411,7 +411,8 @@ extern struct tty_struct *get_current_tty(void);
/* tty_io.c */
extern int __init tty_init(void);
extern const char *tty_name(const struct tty_struct *tty);
-extern struct tty_struct *tty_kopen(dev_t device);
+extern struct tty_struct *tty_kopen_exclusive(dev_t device);
+extern struct tty_struct *tty_kopen_shared(dev_t device);
extern void tty_kclose(struct tty_struct *tty);
extern int tty_dev_name_to_number(const char *name, dev_t *number);
extern int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout);
@@ -436,7 +437,7 @@ static inline int __init tty_init(void)
{ return 0; }
static inline const char *tty_name(const struct tty_struct *tty)
{ return "(none)"; }
-static inline struct tty_struct *tty_kopen(dev_t device)
+static inline struct tty_struct *tty_kopen_exclusive(dev_t device)
{ return ERR_PTR(-ENODEV); }
static inline void tty_kclose(struct tty_struct *tty)
{ }
--
2.24.0
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