Date:   Fri,  8 Dec 2017 15:29:44 +0100
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>
Subject: [PATCH 1/1] HID: core: rewrite the hid-generic automatic unbind

We actually can have the unbind/rebind logic in hid-core.c, leaving
only the match function in hid-generic.
This makes hid-generic simpler and the whole logic simpler too.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
---

Hi Jiri,

while trying to find out a local bug, I figured out we don't really
need the bus_add_driver and bus_removed_driver callbacks.

This makes the code simpler and also allows other drivers to remove
themself if other conditions are met. They just need to implement a smart
enough .matchcallback and they are done.

Cheers,
Benjamin

 drivers/hid/hid-core.c    | 35 ++++++++++++++++++++++++-----------
 drivers/hid/hid-generic.c | 33 ---------------------------------
 include/linux/hid.h       |  4 ----
 3 files changed, 24 insertions(+), 48 deletions(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index c2560aae5542..c058bb911ca1 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -2197,31 +2197,40 @@ void hid_destroy_device(struct hid_device *hdev)
 EXPORT_SYMBOL_GPL(hid_destroy_device);
 
 
-static int __bus_add_driver(struct device_driver *drv, void *data)
+static int __hid_bus_reprobe_drivers(struct device *dev, void *data)
 {
-	struct hid_driver *added_hdrv = data;
-	struct hid_driver *hdrv = to_hid_driver(drv);
+	struct hid_driver *hdrv = data;
+	struct hid_device *hdev = to_hid_device(dev);
 
-	if (hdrv->bus_add_driver)
-		hdrv->bus_add_driver(added_hdrv);
+	if (hdev->driver == hdrv &&
+	    !hdrv->match(hdev, hid_ignore_special_drivers))
+		return device_reprobe(dev);
 
 	return 0;
 }
 
-static int __bus_removed_driver(struct device_driver *drv, void *data)
+static int __hid_bus_driver_added(struct device_driver *drv, void *data)
 {
-	struct hid_driver *removed_hdrv = data;
 	struct hid_driver *hdrv = to_hid_driver(drv);
 
-	if (hdrv->bus_removed_driver)
-		hdrv->bus_removed_driver(removed_hdrv);
+	if (hdrv->match) {
+		bus_for_each_dev(&hid_bus_type, NULL, hdrv,
+				 __hid_bus_reprobe_drivers);
+	}
 
 	return 0;
 }
 
+static int __bus_removed_driver(struct device_driver *drv, void *data)
+{
+	return bus_rescan_devices(&hid_bus_type);
+}
+
 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;
@@ -2230,9 +2239,13 @@ int __hid_register_driver(struct hid_driver *hdrv, struct module *owner,
 	INIT_LIST_HEAD(&hdrv->dyn_list);
 	spin_lock_init(&hdrv->dyn_lock);
 
-	bus_for_each_drv(&hid_bus_type, NULL, hdrv, __bus_add_driver);
+	ret = driver_register(&hdrv->driver);
+
+	if (ret == 0)
+		bus_for_each_drv(&hid_bus_type, NULL, NULL,
+				 __hid_bus_driver_added);
 
-	return driver_register(&hdrv->driver);
+	return ret;
 }
 EXPORT_SYMBOL_GPL(__hid_register_driver);
 
diff --git a/drivers/hid/hid-generic.c b/drivers/hid/hid-generic.c
index 3c0a1bf433d7..c25b4718de44 100644
--- a/drivers/hid/hid-generic.c
+++ b/drivers/hid/hid-generic.c
@@ -26,37 +26,6 @@
 
 static struct hid_driver hid_generic;
 
-static int __unmap_hid_generic(struct device *dev, void *data)
-{
-	struct hid_driver *hdrv = data;
-	struct hid_device *hdev = to_hid_device(dev);
-
-	/* only unbind matching devices already bound to hid-generic */
-	if (hdev->driver != &hid_generic ||
-	    hid_match_device(hdev, hdrv) == NULL)
-		return 0;
-
-	if (dev->parent)	/* Needed for USB */
-		device_lock(dev->parent);
-	device_release_driver(dev);
-	if (dev->parent)
-		device_unlock(dev->parent);
-
-	return 0;
-}
-
-static void hid_generic_add_driver(struct hid_driver *hdrv)
-{
-	bus_for_each_dev(&hid_bus_type, NULL, hdrv, __unmap_hid_generic);
-}
-
-static void hid_generic_removed_driver(struct hid_driver *hdrv)
-{
-	int ret;
-
-	ret = driver_attach(&hid_generic.driver);
-}
-
 static int __check_hid_generic(struct device_driver *drv, void *data)
 {
 	struct hid_driver *hdrv = to_hid_driver(drv);
@@ -97,8 +66,6 @@ static struct hid_driver hid_generic = {
 	.name = "hid-generic",
 	.id_table = hid_table,
 	.match = hid_generic_match,
-	.bus_add_driver = hid_generic_add_driver,
-	.bus_removed_driver = hid_generic_removed_driver,
 };
 module_hid_driver(hid_generic);
 
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 091a81cf330f..a62ee4a609ac 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -686,8 +686,6 @@ struct hid_usage_id {
  * @input_mapped: invoked on input registering after mapping an usage
  * @input_configured: invoked just before the device is registered
  * @feature_mapping: invoked on feature registering
- * @bus_add_driver: invoked when a HID driver is about to be added
- * @bus_removed_driver: invoked when a HID driver has been removed
  * @suspend: invoked on suspend (NULL means nop)
  * @resume: invoked on resume if device was not reset (NULL means nop)
  * @reset_resume: invoked on resume if device was reset (NULL means nop)
@@ -742,8 +740,6 @@ struct hid_driver {
 	void (*feature_mapping)(struct hid_device *hdev,
 			struct hid_field *field,
 			struct hid_usage *usage);
-	void (*bus_add_driver)(struct hid_driver *driver);
-	void (*bus_removed_driver)(struct hid_driver *driver);
 #ifdef CONFIG_PM
 	int (*suspend)(struct hid_device *hdev, pm_message_t message);
 	int (*resume)(struct hid_device *hdev);
-- 
2.14.3

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