[RFC PATCH 1/2] serial: 8250: Add a notifier chain for driver registration.
From: David Daney <hidden>
Date: 2011-03-17 01:26:49
Also in:
linux-serial, lkml
Subsystem:
8250/16?50 (and clone uarts) serial driver, the rest, tty layer and serial drivers · Maintainers:
Greg Kroah-Hartman, Linus Torvalds, Jiri Slaby
The 8250 driver is a bit weird in that in addition to supporting platform devices, extra devices can be added by calling serial8250_register_port(). The problem is that if we call serial8250_register_port() before the driver is initialized Bad Things happen (we dereference NULL pointers). There doesn't seem to be a general way to know if a driver has been initialized, so we add a notifier chain just for this driver. When the SERIAL8250_DRIVER_ADD notifier is called, we know it is safe to call serial8250_register_port(), and we can add our devices. Signed-off-by: David Daney <redacted> --- drivers/tty/serial/8250.c | 20 ++++++++++++++++++++ include/linux/serial_8250.h | 21 +++++++++++++++++++++ 2 files changed, 41 insertions(+), 0 deletions(-)
diff --git a/drivers/tty/serial/8250.c b/drivers/tty/serial/8250.c
index 3975df6..229a1d2 100644
--- a/drivers/tty/serial/8250.c
+++ b/drivers/tty/serial/8250.c@@ -3281,6 +3281,20 @@ void serial8250_unregister_port(int line) } EXPORT_SYMBOL(serial8250_unregister_port); +static BLOCKING_NOTIFIER_HEAD(serial8250_notifier); + +int serial8250_register_notifier(struct notifier_block *nb) +{ + return blocking_notifier_chain_register(&serial8250_notifier, nb); +} +EXPORT_SYMBOL(serial8250_register_notifier); + +int serial8250_unregister_notifier(struct notifier_block *nb) +{ + return blocking_notifier_chain_unregister(&serial8250_notifier, nb); +} +EXPORT_SYMBOL(serial8250_unregister_notifier); + static int __init serial8250_init(void) { int ret;
@@ -3328,6 +3342,10 @@ unreg_uart_drv: uart_unregister_driver(&serial8250_reg); #endif out: + if (ret == 0) + blocking_notifier_call_chain(&serial8250_notifier, + SERIAL8250_DRIVER_ADD, NULL); + return ret; }
@@ -3335,6 +3353,8 @@ static void __exit serial8250_exit(void) { struct platform_device *isa_dev = serial8250_isa_devs; + blocking_notifier_call_chain(&serial8250_notifier, + SERIAL8250_DRIVER_REMOVE, NULL); /* * This tells serial8250_unregister_port() not to re-register * the ports (thereby making serial8250_isa_driver permanently
diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
index 97f5b45..2155c28 100644
--- a/include/linux/serial_8250.h
+++ b/include/linux/serial_8250.h@@ -11,6 +11,7 @@ #ifndef _LINUX_SERIAL_8250_H #define _LINUX_SERIAL_8250_H +#include <linux/notifier.h> #include <linux/serial_core.h> #include <linux/platform_device.h>
@@ -85,4 +86,24 @@ extern void serial8250_set_isa_configurator(void (*v) (int port, struct uart_port *up, unsigned short *capabilities)); +extern int serial8250_register_notifier(struct notifier_block *nb); +extern int serial8250_unregister_notifier(struct notifier_block *nb); +/* + * Notifiers get called to allow serial8250_register_port() after the + * driver is registered, and serial8250_unregister_port() to be called + * before it is unregistered. + */ +#define SERIAL8250_DRIVER_ADD 1 +#define SERIAL8250_DRIVER_REMOVE 2 + +#define serial8250_notifier(fn, pri) \ +({ \ + static struct notifier_block fn##_nb = { \ + .notifier_call = fn, \ + .priority = pri \ + }; \ + \ + serial8250_register_notifier(&fn##_nb); \ +}) + #endif
--
1.7.2.3