[PATCH 12/21] HID: move generic FF initialization into hidinput_connect()

[Dmitry Torokhov]

Generic force-feedback initialization (pidff) currently happens in
hid_connect() after hidinput_connect() has already registered the input
devices. This is racy as the device is live and visible to userspace
before FF support is fully set up.

Move the call to hdev->ff_init() into hidinput_connect(), ensuring it
runs before input_register_device() is called. This closes the race
window for standard PID-capable devices.

The initialization now also checks (connect_mask & HID_CONNECT_FF) and
!hid_has_ff_input() to avoid conflicts with custom FF implementations
and respect driver opt-outs.

Assisted-by: Gemini:gemini-3.1-pro
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
---
 drivers/hid/hid-core.c  | 21 ++-------------------
 drivers/hid/hid-input.c | 21 +++++++++++++++++++--
 include/linux/hid.h     |  2 +-
 3 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 2767a171eae9..d8cba852d2b5 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -2287,18 +2287,6 @@ static const BIN_ATTR_RO(report_descriptor, HID_MAX_DESCRIPTOR_SIZE);
 
 static const DEVICE_ATTR_RO(country);
 
-static bool hid_has_ff_input(struct hid_device *hdev)
-{
-	struct hid_input *hidinput;
-
-	list_for_each_entry(hidinput, &hdev->inputs, list) {
-		if (test_bit(EV_FF, hidinput->input->evbit))
-			return true;
-	}
-
-	return false;
-}
-
 int hid_connect(struct hid_device *hdev, unsigned int connect_mask)
 {
 	static const char *types[] = { "Device", "Pointer", "Mouse", "Device",
@@ -2324,8 +2312,8 @@ int hid_connect(struct hid_device *hdev, unsigned int connect_mask)
 	if (hid_hiddev(hdev))
 		connect_mask |= HID_CONNECT_HIDDEV_FORCE;
 
-	if ((connect_mask & HID_CONNECT_HIDINPUT) && !hidinput_connect(hdev,
-				connect_mask & HID_CONNECT_HIDINPUT_FORCE))
+	if ((connect_mask & HID_CONNECT_HIDINPUT) &&
+	    !hidinput_connect(hdev, connect_mask))
 		hdev->claimed |= HID_CLAIMED_INPUT;
 
 	if ((connect_mask & HID_CONNECT_HIDDEV) && hdev->hiddev_connect &&
@@ -2347,11 +2335,6 @@ int hid_connect(struct hid_device *hdev, unsigned int connect_mask)
 
 	hid_process_ordering(hdev);
 
-	if ((hdev->claimed & HID_CLAIMED_INPUT) &&
-			(connect_mask & HID_CONNECT_FF) && hdev->ff_init &&
-			!hid_has_ff_input(hdev))
-		hdev->ff_init(hdev);
-
 	len = 0;
 	if (hdev->claimed & HID_CLAIMED_INPUT)
 		len += sprintf(buf + len, "input");
diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index 3487600cadb4..70ec1b7e7d38 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -2317,7 +2317,19 @@ static inline void hidinput_configure_usages(struct hid_input *hidinput,
  * Read all reports and initialize the absolute field values.
  */
 
-int hidinput_connect(struct hid_device *hid, unsigned int force)
+static bool hid_has_ff_input(struct hid_device *hdev)
+{
+	struct hid_input *hidinput;
+
+	list_for_each_entry(hidinput, &hdev->inputs, list) {
+		if (test_bit(EV_FF, hidinput->input->evbit))
+			return true;
+	}
+
+	return false;
+}
+
+int hidinput_connect(struct hid_device *hid, unsigned int connect_mask)
 {
 	struct hid_driver *drv = hid->driver;
 	struct hid_report *report;
@@ -2330,7 +2342,7 @@ int hidinput_connect(struct hid_device *hid, unsigned int force)
 
 	hid->status &= ~HID_STAT_DUP_DETECTED;
 
-	if (!force) {
+	if (!(connect_mask & HID_CONNECT_HIDINPUT_FORCE)) {
 		for (i = 0; i < hid->maxcollection; i++) {
 			struct hid_collection *col = &hid->collection[i];
 			if (col->type == HID_COLLECTION_APPLICATION ||
@@ -2396,6 +2408,11 @@ int hidinput_connect(struct hid_device *hid, unsigned int force)
 			continue;
 		}
 
+		if (list_is_first(&hidinput->list, &hid->inputs) &&
+		    (connect_mask & HID_CONNECT_FF) && hid->ff_init &&
+		    !hid_has_ff_input(hid))
+			hid->ff_init(hid);
+
 		if (input_register_device(hidinput->input))
 			goto out_unwind;
 		hidinput->registered = true;
diff --git a/include/linux/hid.h b/include/linux/hid.h
index b240baa95ab5..451c3e05d167 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -1021,7 +1021,7 @@ extern void hid_unregister_driver(struct hid_driver *);
 
 extern void hidinput_hid_event(struct hid_device *, struct hid_field *, struct hid_usage *, __s32);
 extern void hidinput_report_event(struct hid_device *hid, struct hid_report *report);
-extern int hidinput_connect(struct hid_device *hid, unsigned int force);
+extern int hidinput_connect(struct hid_device *hid, unsigned int connect_mask);
 extern void hidinput_disconnect(struct hid_device *);
 void hidinput_reset_resume(struct hid_device *hid);
 

-- 
2.55.0.629.g250fe7f194-goog