Driver core: udev triggered device-<>driver binding

We get two per-bus sysfs files:
  ls-l /sys/subsystem/usb
  drwxr-xr-x 2 root root    0 2007-02-16 16:42 devices
  drwxr-xr-x 7 root root    0 2007-02-16 14:55 drivers
  -rw-r--r-- 1 root root 4096 2007-02-16 16:42 drivers_autoprobe
  --w------- 1 root root 4096 2007-02-16 16:42 drivers_probe

The flag "drivers_autoprobe" controls the behavior of the bus to bind
devices by default, or just initialize the device and leave it alone.

The command "drivers_probe" accepts a bus_id and the bus tries to bind a
driver to this device.

Systems who want to control the driver binding with udev, switch off the
bus initiated probing:
  echo 0 > /sys/subsystem/usb/drivers_autoprobe
  echo 0 > /sys/subsystem/pcmcia/drivers_autoprobe
  ...

and initiate the probing with udev rules like:
  ACTION=="add", SUBSYSTEM=="usb", ATTR{subsystem/drivers_probe}="$kernel"
  ACTION=="add", SUBSYSTEM=="pcmcia", ATTR{subsystem/drivers_probe}="$kernel"
  ...

Custom driver binding can happen in earlier rules by something like:
  ACTION=="add", SUBSYSTEM=="usb", \
  ATTRS{idVendor}=="1234", ATTRS{idProduct}=="5678" \
  ATTR{subsystem/drivers/<custom-driver>/bind}="$kernel"

This is intended to solve the modprobe.conf mess with "install-rules", custom
bind/unbind-scripts and all the weird things people invented over the years.
It should also provide the functionality "libusual" was supposed to do.

With udev, one can just write a udev rule to drive all USB-disks at the
third port of USB-hub by the "ub" driver, and everything else by
usb-storage. One can also instruct udev to bind different wireless
drivers to identical cards - just selected by the pcmcia slot-number, and
whatever ...

To use the mentioned rules, it needs udev version 106, to be able to
write ATTR{}="$kernel" to sysfs files.

Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 97 insertions, 21 deletions

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index 253868e03c70..9df2e6dff519 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -27,6 +27,9 @@
 #define to_driver(obj) container_of(obj, struct device_driver, kobj)
 
 
+static int __must_check bus_rescan_devices_helper(struct device *dev,
+                                                void *data);
+
 static ssize_t
 drv_attr_show(struct kobject * kobj, struct attribute * attr, char * buf)
 {
@@ -133,7 +136,6 @@ static decl_subsys(bus, &ktype_bus, NULL);
 
 
 #ifdef CONFIG_HOTPLUG
-
 /* Manually detach a device from its associated driver. */
 static int driver_helper(struct device *dev, void *data)
 {
@@ -199,6 +201,33 @@ static ssize_t driver_bind(struct device_driver *drv,
 }
 static DRIVER_ATTR(bind, S_IWUSR, NULL, driver_bind);
 
+static ssize_t show_drivers_autoprobe(struct bus_type *bus, char *buf)
+{
+        return sprintf(buf, "%d\n", bus->drivers_autoprobe);
+}
+
+static ssize_t store_drivers_autoprobe(struct bus_type *bus,
+                                       const char *buf, size_t count)
+{
+        if (buf[0] == '0')
+                bus->drivers_autoprobe = 0;
+        else
+                bus->drivers_autoprobe = 1;
+        return count;
+}
+
+static ssize_t store_drivers_probe(struct bus_type *bus,
+                                   const char *buf, size_t count)
+{
+        struct device *dev;
+
+        dev = bus_find_device(bus, NULL, (void *)buf, driver_helper);
+        if (!dev)
+                return -ENODEV;
+        if (bus_rescan_devices_helper(dev, NULL) != 0)
+                return -EINVAL;
+        return count;
+}
 #endif
 
 static struct device * next_device(struct klist_iter * i)
@@ -425,7 +454,8 @@ int bus_attach_device(struct device * dev)
 
         if (bus) {
                 dev->is_registered = 1;
-                ret = device_attach(dev);
+                if (bus->drivers_autoprobe)
+                        ret = device_attach(dev);
                 if (ret >= 0) {
                         klist_add_tail(&dev->knode_bus, &bus->klist_devices);
                         ret = 0;
@@ -515,9 +545,41 @@ static void remove_bind_files(struct device_driver *drv)
         driver_remove_file(drv, &driver_attr_bind);
         driver_remove_file(drv, &driver_attr_unbind);
 }
+
+static int add_probe_files(struct bus_type *bus)
+{
+        int retval;
+
+        bus->drivers_probe_attr.attr.name = "drivers_probe";
+        bus->drivers_probe_attr.attr.mode = S_IWUSR;
+        bus->drivers_probe_attr.attr.owner = bus->owner;
+        bus->drivers_probe_attr.store = store_drivers_probe;
+        retval = bus_create_file(bus, &bus->drivers_probe_attr);
+        if (retval)
+                goto out;
+
+        bus->drivers_autoprobe_attr.attr.name = "drivers_autoprobe";
+        bus->drivers_autoprobe_attr.attr.mode = S_IWUSR | S_IRUGO;
+        bus->drivers_autoprobe_attr.attr.owner = bus->owner;
+        bus->drivers_autoprobe_attr.show = show_drivers_autoprobe;
+        bus->drivers_autoprobe_attr.store = store_drivers_autoprobe;
+        retval = bus_create_file(bus, &bus->drivers_autoprobe_attr);
+        if (retval)
+                bus_remove_file(bus, &bus->drivers_probe_attr);
+out:
+        return retval;
+}
+
+static void remove_probe_files(struct bus_type *bus)
+{
+        bus_remove_file(bus, &bus->drivers_autoprobe_attr);
+        bus_remove_file(bus, &bus->drivers_probe_attr);
+}
 #else
 static inline int add_bind_files(struct device_driver *drv) { return 0; }
 static inline void remove_bind_files(struct device_driver *drv) {}
+static inline int add_probe_files(struct bus_type *bus) { return 0; }
+static inline void remove_probe_files(struct bus_type *bus) {}
 #endif
 
 /**
@@ -541,9 +603,11 @@ int bus_add_driver(struct device_driver *drv)
         if ((error = kobject_register(&drv->kobj)))
                 goto out_put_bus;
 
-        error = driver_attach(drv);
-        if (error)
-                goto out_unregister;
+        if (drv->bus->drivers_autoprobe) {
+                error = driver_attach(drv);
+                if (error)
+                        goto out_unregister;
+        }
         klist_add_tail(&drv->knode_bus, &bus->klist_drivers);
         module_add_driver(drv->owner, drv);
 
@@ -762,6 +826,12 @@ int bus_register(struct bus_type * bus)
 
         klist_init(&bus->klist_devices, klist_devices_get, klist_devices_put);
         klist_init(&bus->klist_drivers, NULL, NULL);
+
+        bus->drivers_autoprobe = 1;
+        retval = add_probe_files(bus);
+        if (retval)
+                goto bus_probe_files_fail;
+
         retval = bus_add_attrs(bus);
         if (retval)
                 goto bus_attrs_fail;
@@ -770,6 +840,8 @@ int bus_register(struct bus_type * bus)
         return 0;
 
 bus_attrs_fail:
+        remove_probe_files(bus);
+bus_probe_files_fail:
         kset_unregister(&bus->drivers);
 bus_drivers_fail:
         kset_unregister(&bus->devices);
@@ -779,7 +851,6 @@ out:
         return retval;
 }
 
-
 /**
  *      bus_unregister - remove a bus from the system
  *      @bus:   bus.
@@ -791,6 +862,7 @@ void bus_unregister(struct bus_type * bus)
 {
         pr_debug("bus %s: unregistering\n", bus->name);
         bus_remove_attrs(bus);
+        remove_probe_files(bus);
         kset_unregister(&bus->drivers);
         kset_unregister(&bus->devices);
         subsystem_unregister(&bus->subsys);
diff --git a/include/linux/device.h b/include/linux/device.h
index de0e73eae6bc..9d54fe13eb2e 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -34,9 +34,24 @@ struct device;
 struct device_driver;
 struct class;
 struct class_device;
+struct bus_type;
+
+struct bus_attribute {
+        struct attribute        attr;
+        ssize_t (*show)(struct bus_type *, char * buf);
+        ssize_t (*store)(struct bus_type *, const char * buf, size_t count);
+};
+
+#define BUS_ATTR(_name,_mode,_show,_store)      \
+struct bus_attribute bus_attr_##_name = __ATTR(_name,_mode,_show,_store)
+
+extern int __must_check bus_create_file(struct bus_type *,
+                                        struct bus_attribute *);
+extern void bus_remove_file(struct bus_type *, struct bus_attribute *);
 
 struct bus_type {
         const char              * name;
+        struct module           * owner;
 
         struct subsystem        subsys;
         struct kset             drivers;
@@ -49,6 +64,8 @@ struct bus_type {
         struct bus_attribute    * bus_attrs;
         struct device_attribute * dev_attrs;
         struct driver_attribute * drv_attrs;
+        struct bus_attribute drivers_autoprobe_attr;
+        struct bus_attribute drivers_probe_attr;
 
         int             (*match)(struct device * dev, struct device_driver * drv);
         int             (*uevent)(struct device *dev, char **envp,
@@ -61,6 +78,8 @@ struct bus_type {
         int (*suspend_late)(struct device * dev, pm_message_t state);
         int (*resume_early)(struct device * dev);
         int (*resume)(struct device * dev);
+
+        unsigned int drivers_autoprobe:1;
 };
 
 extern int __must_check bus_register(struct bus_type * bus);
@@ -102,21 +121,6 @@ extern int bus_unregister_notifier(struct bus_type *bus,
 #define BUS_NOTIFY_UNBIND_DRIVER        0x00000004 /* driver about to be
                                                       unbound */
 
-/* sysfs interface for exporting bus attributes */
-
-struct bus_attribute {
-        struct attribute        attr;
-        ssize_t (*show)(struct bus_type *, char * buf);
-        ssize_t (*store)(struct bus_type *, const char * buf, size_t count);
-};
-
-#define BUS_ATTR(_name,_mode,_show,_store)      \
-struct bus_attribute bus_attr_##_name = __ATTR(_name,_mode,_show,_store)
-
-extern int __must_check bus_create_file(struct bus_type *,
-                                        struct bus_attribute *);
-extern void bus_remove_file(struct bus_type *, struct bus_attribute *);
-
 struct device_driver {
         const char              * name;
         struct bus_type         * bus;