HID: add dynids facility

Allow adding new devices to the hid drivers on the fly without
a need of kernel recompilation.

Now, one can test a driver e.g. by:
echo 0003:045E:00F0.0003 > ../generic-usb/unbind
echo 0003 045E 00F0 > new_id
from some driver subdir.

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

2 files changed, 103 insertions, 3 deletions

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 344f8fdb2824..34cc3b0d01f6 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -1304,12 +1304,92 @@ static const struct hid_device_id hid_blacklist[] = {
         { }
 };
 
+struct hid_dynid {
+        struct list_head list;
+        struct hid_device_id id;
+};
+
+/**
+ * store_new_id - add a new HID device ID to this driver and re-probe devices
+ * @driver: target device driver
+ * @buf: buffer for scanning device ID data
+ * @count: input size
+ *
+ * Adds a new dynamic hid device ID to this driver,
+ * and causes the driver to probe for all devices again.
+ */
+static ssize_t store_new_id(struct device_driver *drv, const char *buf,
+                size_t count)
+{
+        struct hid_driver *hdrv = container_of(drv, struct hid_driver, driver);
+        struct hid_dynid *dynid;
+        __u32 bus, vendor, product;
+        unsigned long driver_data = 0;
+        int ret;
+
+        ret = sscanf(buf, "%x %x %x %lx",
+                        &bus, &vendor, &product, &driver_data);
+        if (ret < 3)
+                return -EINVAL;
+
+        dynid = kzalloc(sizeof(*dynid), GFP_KERNEL);
+        if (!dynid)
+                return -ENOMEM;
+
+        dynid->id.bus = bus;
+        dynid->id.vendor = vendor;
+        dynid->id.product = product;
+        dynid->id.driver_data = driver_data;
+
+        spin_lock(&hdrv->dyn_lock);
+        list_add_tail(&dynid->list, &hdrv->dyn_list);
+        spin_unlock(&hdrv->dyn_lock);
+
+        ret = 0;
+        if (get_driver(&hdrv->driver)) {
+                ret = driver_attach(&hdrv->driver);
+                put_driver(&hdrv->driver);
+        }
+
+        return ret ? : count;
+}
+static DRIVER_ATTR(new_id, S_IWUSR, NULL, store_new_id);
+
+static void hid_free_dynids(struct hid_driver *hdrv)
+{
+        struct hid_dynid *dynid, *n;
+
+        spin_lock(&hdrv->dyn_lock);
+        list_for_each_entry_safe(dynid, n, &hdrv->dyn_list, list) {
+                list_del(&dynid->list);
+                kfree(dynid);
+        }
+        spin_unlock(&hdrv->dyn_lock);
+}
+
+static const struct hid_device_id *hid_match_device(struct hid_device *hdev,
+                struct hid_driver *hdrv)
+{
+        struct hid_dynid *dynid;
+
+        spin_lock(&hdrv->dyn_lock);
+        list_for_each_entry(dynid, &hdrv->dyn_list, list) {
+                if (hid_match_one_id(hdev, &dynid->id)) {
+                        spin_unlock(&hdrv->dyn_lock);
+                        return &dynid->id;
+                }
+        }
+        spin_unlock(&hdrv->dyn_lock);
+
+        return hid_match_id(hdev, hdrv->id_table);
+}
+
 static int hid_bus_match(struct device *dev, struct device_driver *drv)
 {
         struct hid_driver *hdrv = container_of(drv, struct hid_driver, driver);
         struct hid_device *hdev = container_of(dev, struct hid_device, dev);
 
-        if (!hid_match_id(hdev, hdrv->id_table))
+        if (!hid_match_device(hdev, hdrv))
                 return 0;
 
         /* generic wants all non-blacklisted */
@@ -1328,7 +1408,7 @@ static int hid_device_probe(struct device *dev)
         int ret = 0;
 
         if (!hdev->driver) {
-                id = hid_match_id(hdev, hdrv->id_table);
+                id = hid_match_device(hdev, hdrv);
                 if (id == NULL)
                         return -ENODEV;
 
@@ -1695,18 +1775,33 @@ EXPORT_SYMBOL_GPL(hid_destroy_device);
 int __hid_register_driver(struct hid_driver *hdrv, struct module *owner,
                 const char *mod_name)
 {
+        int ret;
+
         hdrv->driver.name = hdrv->name;
         hdrv->driver.bus = &hid_bus_type;
         hdrv->driver.owner = owner;
         hdrv->driver.mod_name = mod_name;
 
-        return driver_register(&hdrv->driver);
+        INIT_LIST_HEAD(&hdrv->dyn_list);
+        spin_lock_init(&hdrv->dyn_lock);
+
+        ret = driver_register(&hdrv->driver);
+        if (ret)
+                return ret;
+
+        ret = driver_create_file(&hdrv->driver, &driver_attr_new_id);
+        if (ret)
+                driver_unregister(&hdrv->driver);
+
+        return ret;
 }
 EXPORT_SYMBOL_GPL(__hid_register_driver);
 
 void hid_unregister_driver(struct hid_driver *hdrv)
 {
+        driver_remove_file(&hdrv->driver, &driver_attr_new_id);
         driver_unregister(&hdrv->driver);
+        hid_free_dynids(hdrv);
 }
 EXPORT_SYMBOL_GPL(hid_unregister_driver);
 
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 2c20f20283b2..215035bbb288 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -531,6 +531,8 @@ struct hid_usage_id {
  * @name: driver name (e.g. "Footech_bar-wheel")
  * @id_table: which devices is this driver for (must be non-NULL for probe
  *            to be called)
+ * @dyn_list: list of dynamically added device ids
+ * @dyn_lock: lock protecting @dyn_list
  * @probe: new device inserted
  * @remove: device removed (NULL if not a hot-plug capable driver)
  * @report_table: on which reports to call raw_event (NULL means all)
@@ -558,6 +560,9 @@ struct hid_driver {
         char *name;
         const struct hid_device_id *id_table;
 
+        struct list_head dyn_list;
+        spinlock_t dyn_lock;
+
         int (*probe)(struct hid_device *dev, const struct hid_device_id *id);
         void (*remove)(struct hid_device *dev);