[PATCH v2 0/2] serdev: fix broken lifetime assumptions

[PATCH v2 0/2] serdev: fix broken lifetime assumptions

[Johan Hovold]

This series fixes a number of issues with the new serdev code, which was
based on incorrect tty-port lifetime assumptions.

The first patch in v1 of this series disables serdev support by reverting the
patch which hooked into the tty layer in a broken way that leads to crashes and
leaks when deregistering devices. That one has now been applied to tty-linus
with a stable tag (for v4.11).

The remaining two patches again re-enables serdev (first enabled in 4.11, but
soon reverted in stable) for a subset of tty drivers by adding adding a new
interface for registering serdev devices and using that in serial core only.

More details can be found in the individual commit messages.

Johan


Changes in v2
 - rebase on tty-linus
 - drop first two patches that have already been applied
 - remove a stray newline in patch 1/2
 - add Rob's reviewed-by tag


Johan Hovold (2):
  tty/serdev: add serdev registration interface
  serial: enable serdev support

 drivers/tty/serdev/serdev-ttyport.c |  6 ++-
 drivers/tty/serial/serial_core.c    |  4 +-
 drivers/tty/tty_port.c              | 75 +++++++++++++++++++++++++++++++++++++
 include/linux/serdev.h              |  7 +++-
 include/linux/tty.h                 |  9 +++++
 5 files changed, 95 insertions(+), 6 deletions(-)

-- 
2.13.0

[PATCH v2 1/2] tty/serdev: add serdev registration interface

[Johan Hovold]

Add a new interface for registering a serdev controller and clients, and
a helper function to deregister serdev devices (or a tty device) that
were previously registered using the new interface.

Once every driver currently using the tty_port_register_device() helpers
have been vetted and converted to use the new serdev registration
interface (at least for deregistration), we can move serdev registration
to the current helpers and get rid of the serdev-specific functions.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/tty/serdev/serdev-ttyport.c |  6 ++-
 drivers/tty/tty_port.c              | 75 +++++++++++++++++++++++++++++++++++++
 include/linux/serdev.h              |  7 +++-
 include/linux/tty.h                 |  9 +++++
 4 files changed, 93 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serdev/serdev-ttyport.c b/drivers/tty/serdev/serdev-ttyport.c
index 013efffd2e82..d0a021c93986 100644
--- a/drivers/tty/serdev/serdev-ttyport.c
+++ b/drivers/tty/serdev/serdev-ttyport.c
@@ -250,16 +250,18 @@ struct device *serdev_tty_port_register(struct tty_port *port,
 	return ERR_PTR(ret);
 }
 
-void serdev_tty_port_unregister(struct tty_port *port)
+int serdev_tty_port_unregister(struct tty_port *port)
 {
 	struct serdev_controller *ctrl = port->client_data;
 	struct serport *serport = serdev_controller_get_drvdata(ctrl);
 
 	if (!serport)
-		return;
+		return -ENODEV;
 
 	serdev_controller_remove(ctrl);
 	port->client_ops = NULL;
 	port->client_data = NULL;
 	serdev_controller_put(ctrl);
+
+	return 0;
 }
diff --git a/drivers/tty/tty_port.c b/drivers/tty/tty_port.c
index 88dac3b79369..4fb3165384c4 100644
--- a/drivers/tty/tty_port.c
+++ b/drivers/tty/tty_port.c
@@ -16,6 +16,7 @@
 #include <linux/bitops.h>
 #include <linux/delay.h>
 #include <linux/module.h>
+#include <linux/serdev.h>
 
 static int tty_port_default_receive_buf(struct tty_port *port,
 					const unsigned char *p,
@@ -136,6 +137,80 @@ struct device *tty_port_register_device_attr(struct tty_port *port,
 }
 EXPORT_SYMBOL_GPL(tty_port_register_device_attr);
 
+/**
+ * tty_port_register_device_attr_serdev - register tty or serdev device
+ * @port: tty_port of the device
+ * @driver: tty_driver for this device
+ * @index: index of the tty
+ * @device: parent if exists, otherwise NULL
+ * @drvdata: driver data for the device
+ * @attr_grp: attribute group for the device
+ *
+ * Register a serdev or tty device depending on if the parent device has any
+ * defined serdev clients or not.
+ */
+struct device *tty_port_register_device_attr_serdev(struct tty_port *port,
+		struct tty_driver *driver, unsigned index,
+		struct device *device, void *drvdata,
+		const struct attribute_group **attr_grp)
+{
+	struct device *dev;
+
+	tty_port_link_device(port, driver, index);
+
+	dev = serdev_tty_port_register(port, device, driver, index);
+	if (PTR_ERR(dev) != -ENODEV) {
+		/* Skip creating cdev if we registered a serdev device */
+		return dev;
+	}
+
+	return tty_register_device_attr(driver, index, device, drvdata,
+			attr_grp);
+}
+EXPORT_SYMBOL_GPL(tty_port_register_device_attr_serdev);
+
+/**
+ * tty_port_register_device_serdev - register tty or serdev device
+ * @port: tty_port of the device
+ * @driver: tty_driver for this device
+ * @index: index of the tty
+ * @device: parent if exists, otherwise NULL
+ *
+ * Register a serdev or tty device depending on if the parent device has any
+ * defined serdev clients or not.
+ */
+struct device *tty_port_register_device_serdev(struct tty_port *port,
+		struct tty_driver *driver, unsigned index,
+		struct device *device)
+{
+	return tty_port_register_device_attr_serdev(port, driver, index,
+			device, NULL, NULL);
+}
+EXPORT_SYMBOL_GPL(tty_port_register_device_serdev);
+
+/**
+ * tty_port_unregister_device - deregister a tty or serdev device
+ * @port: tty_port of the device
+ * @driver: tty_driver for this device
+ * @index: index of the tty
+ *
+ * If a tty or serdev device is registered with a call to
+ * tty_port_register_device_serdev() then this function must be called when
+ * the device is gone.
+ */
+void tty_port_unregister_device(struct tty_port *port,
+		struct tty_driver *driver, unsigned index)
+{
+	int ret;
+
+	ret = serdev_tty_port_unregister(port);
+	if (ret == 0)
+		return;
+
+	tty_unregister_device(driver, index);
+}
+EXPORT_SYMBOL_GPL(tty_port_unregister_device);
+
 int tty_port_alloc_xmit_buf(struct tty_port *port)
 {
 	/* We may sleep in get_zeroed_page() */
diff --git a/include/linux/serdev.h b/include/linux/serdev.h
index e2a225bf716d..e69402d4a8ae 100644
--- a/include/linux/serdev.h
+++ b/include/linux/serdev.h
@@ -308,7 +308,7 @@ struct tty_driver;
 struct device *serdev_tty_port_register(struct tty_port *port,
 					struct device *parent,
 					struct tty_driver *drv, int idx);
-void serdev_tty_port_unregister(struct tty_port *port);
+int serdev_tty_port_unregister(struct tty_port *port);
 #else
 static inline struct device *serdev_tty_port_register(struct tty_port *port,
 					   struct device *parent,
@@ -316,7 +316,10 @@ static inline struct device *serdev_tty_port_register(struct tty_port *port,
 {
 	return ERR_PTR(-ENODEV);
 }
-static inline void serdev_tty_port_unregister(struct tty_port *port) {}
+static inline int serdev_tty_port_unregister(struct tty_port *port)
+{
+	return -ENODEV;
+}
 #endif /* CONFIG_SERIAL_DEV_CTRL_TTYPORT */
 
 #endif /*_LINUX_SERDEV_H */
diff --git a/include/linux/tty.h b/include/linux/tty.h
index d07cd2105a6c..eccb4ec30a8a 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -558,6 +558,15 @@ extern struct device *tty_port_register_device_attr(struct tty_port *port,
 		struct tty_driver *driver, unsigned index,
 		struct device *device, void *drvdata,
 		const struct attribute_group **attr_grp);
+extern struct device *tty_port_register_device_serdev(struct tty_port *port,
+		struct tty_driver *driver, unsigned index,
+		struct device *device);
+extern struct device *tty_port_register_device_attr_serdev(struct tty_port *port,
+		struct tty_driver *driver, unsigned index,
+		struct device *device, void *drvdata,
+		const struct attribute_group **attr_grp);
+extern void tty_port_unregister_device(struct tty_port *port,
+		struct tty_driver *driver, unsigned index);
 extern int tty_port_alloc_xmit_buf(struct tty_port *port);
 extern void tty_port_free_xmit_buf(struct tty_port *port);
 extern void tty_port_destroy(struct tty_port *port);
-- 
2.13.0

[PATCH v2 2/2] serial: enable serdev support

[Johan Hovold]

Enable serdev support by using the new device-registration helpers.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/tty/serial/serial_core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index bc6caea6099f..13bfd5dcffce 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2782,7 +2782,7 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
 	 * Register the port whether it's detected or not.  This allows
 	 * setserial to be used to alter this port's parameters.
 	 */
-	tty_dev = tty_port_register_device_attr(port, drv->tty_driver,
+	tty_dev = tty_port_register_device_attr_serdev(port, drv->tty_driver,
 			uport->line, uport->dev, port, uport->tty_groups);
 	if (likely(!IS_ERR(tty_dev))) {
 		device_set_wakeup_capable(tty_dev, 1);
@@ -2845,7 +2845,7 @@ int uart_remove_one_port(struct uart_driver *drv, struct uart_port *uport)
 	/*
 	 * Remove the devices from the tty layer
 	 */
-	tty_unregister_device(drv->tty_driver, uport->line);
+	tty_port_unregister_device(port, drv->tty_driver, uport->line);
 
 	tty = tty_port_tty_get(port);
 	if (tty) {
-- 
2.13.0