HID: add compat support

Add compat option to hid code to allow loading of all modules on
systems which don't allow autoloading because of old userspace.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

Documentation/feature-removal-schedule.txt

@@ -287,6 +287,13 @@ Who:	Glauber Costa <gcosta@redhat.com>
 
 ---------------------------
 
+What:	remove HID compat support
+When:	2.6.29
+Why:	needed only as a temporary solution until distros fix themselves up
+Who:	Jiri Slaby <jirislaby@gmail.com>
+
+---------------------------
+
 What:	/sys/o2cb symlink
 When:	January 2010
 Why:	/sys/fs/o2cb is the proper location for this information - /sys/o2cb

drivers/hid/Kconfig

@@ -70,6 +70,18 @@ source "drivers/hid/usbhid/Kconfig"
 menu "Special HID drivers"
 	depends on HID
 
+config HID_COMPAT
+	bool "Load all HID drivers on hid core load"
+	default y
+	---help---
+	Compatible option for older userspace. If you have system without udev
+	support of module loading through aliases and also old
+	module-init-tools which can't handle hid bus, choose Y here. Otherwise
+	say N. If you say N and your userspace is old enough, the only
+	functionality you loose is modules autoloading.
+
+	If unsure, say Y.
+
 config HID_APPLE
 	tristate "Apple"
 	default m

drivers/hid/Makefile

@@ -8,6 +8,10 @@ obj-$(CONFIG_HID)		+= hid.o
 hid-$(CONFIG_HID_DEBUG)		+= hid-debug.o
 hid-$(CONFIG_HIDRAW)		+= hidraw.o
 
+ifdef CONFIG_HID_COMPAT
+obj-m				+= hid-dummy.o
+endif
+
 obj-$(CONFIG_HID_APPLE)		+= hid-apple.o
 obj-$(CONFIG_HID_LOGITECH)	+= hid-logitech.o
 

drivers/hid/hid-apple.c

@@ -477,3 +477,5 @@ static void apple_exit(void)
 module_init(apple_init);
 module_exit(apple_exit);
 MODULE_LICENSE("GPL");
+
+HID_COMPAT_LOAD_DRIVER(apple);

drivers/hid/hid-core.c

@@ -1532,6 +1532,14 @@ void hid_unregister_driver(struct hid_driver *hdrv)
 }
 EXPORT_SYMBOL_GPL(hid_unregister_driver);
 
+#ifdef CONFIG_HID_COMPAT
+static void hid_compat_load(struct work_struct *ws)
+{
+	request_module("hid-dummy");
+}
+static DECLARE_WORK(hid_compat_work, hid_compat_load);
+#endif
+
 static int __init hid_init(void)
 {
 	int ret;
@@ -1546,6 +1554,10 @@ static int __init hid_init(void)
 	if (ret)
 		goto err_bus;
 
+#ifdef CONFIG_HID_COMPAT
+	schedule_work(&hid_compat_work);
+#endif
+
 	return 0;
 err_bus:
 	bus_unregister(&hid_bus_type);

drivers/hid/hid-dummy.c

@@ -0,0 +1,18 @@
+#include <linux/autoconf.h>
+#include <linux/module.h>
+#include <linux/hid.h>
+
+static int __init hid_dummy_init(void)
+{
+#ifdef CONFIG_HID_APPLE_MODULE
+	HID_COMPAT_CALL_DRIVER(apple);
+#endif
+#ifdef CONFIG_HID_LOGITECH_MODULE
+	HID_COMPAT_CALL_DRIVER(logitech);
+#endif
+
+	return -EIO;
+}
+module_init(hid_dummy_init);
+
+MODULE_LICENSE("GPL");

drivers/hid/hid-logitech.c

@@ -310,3 +310,5 @@ static void lg_exit(void)
 module_init(lg_init);
 module_exit(lg_exit);
 MODULE_LICENSE("GPL");
+
+HID_COMPAT_LOAD_DRIVER(logitech);

include/linux/hid.h

@@ -790,10 +790,23 @@ dbg_hid(const char *fmt, ...)
 	return 0;
 }
 #define dbg_hid_line dbg_hid
-#endif
+#endif /* HID_DEBUG */
 
 #define err_hid(format, arg...) printk(KERN_ERR "%s: " format "\n" , \
 		__FILE__ , ## arg)
-#endif
+#endif /* HID_FF */
+
+#ifdef CONFIG_HID_COMPAT
+#define HID_COMPAT_LOAD_DRIVER(name)	\
+void hid_compat_##name(void) { }	\
+EXPORT_SYMBOL(hid_compat_##name)
+#else
+#define HID_COMPAT_LOAD_DRIVER(name)
+#endif /* HID_COMPAT */
+#define HID_COMPAT_CALL_DRIVER(name)	do {	\
+	extern void hid_compat_##name(void);	\
+	hid_compat_##name();			\
+} while (0)
+
 #endif