[PATCH 07/21] HID: emsff: move FF initialization to .input_configured()

The driver currently initializes force-feedback in its probe() function
after calling hid_hw_start() with HID_CONNECT_DEFAULT. This is racy as
the input device is already registered and visible to userspace at that
point.

Move the FF initialization to the .input_configured() callback to ensure
the device is fully prepared before registration.

Assisted-by: Gemini:gemini-3.1-pro
Signed-off-by: Dmitry Torokhov <[email protected]>
---
 drivers/hid/hid-emsff.c | 50 ++++++++-----------------------------------------
 1 file changed, 8 insertions(+), 42 deletions(-)

diff --git a/drivers/hid/hid-emsff.c b/drivers/hid/hid-emsff.c
index 1b4ad18f6051..d8e559e0524f 100644
--- a/drivers/hid/hid-emsff.c
+++ b/drivers/hid/hid-emsff.c
@@ -43,29 +43,23 @@ static int emsff_play(struct input_dev *dev, void *data,
 	return 0;
 }
 
-static int emsff_init(struct hid_device *hid)
+static int ems_input_configured(struct hid_device *hid, struct hid_input *hidinput)
 {
 	struct emsff_device *emsff;
 	struct hid_report *report;
-	struct hid_input *hidinput;
 	struct list_head *report_list =
 			&hid->report_enum[HID_OUTPUT_REPORT].report_list;
-	struct input_dev *dev;
+	struct input_dev *dev = hidinput->input;
 	int error;
 
-	if (list_empty(&hid->inputs)) {
-		hid_err(hid, "no inputs found\n");
-		return -ENODEV;
-	}
-	hidinput = list_first_entry(&hid->inputs, struct hid_input, list);
-	dev = hidinput->input;
+	if (!list_is_first(&hidinput->list, &hid->inputs))
+		return 0;
 
-	if (list_empty(report_list)) {
+	report = list_first_entry_or_null(report_list, struct hid_report, list);
+	if (!report) {
 		hid_err(hid, "no output reports found\n");
 		return -ENODEV;
 	}
-
-	report = list_first_entry(report_list, struct hid_report, list);
 	if (report->maxfield < 1) {
 		hid_err(hid, "no fields in the report\n");
 		return -ENODEV;
@@ -80,6 +74,7 @@ static int emsff_init(struct hid_device *hid)
 	if (!emsff)
 		return -ENOMEM;
 
+	emsff->report = report;
 	set_bit(FF_RUMBLE, dev->ffbit);
 
 	error = input_ff_create_memless(dev, emsff, emsff_play);
@@ -88,7 +83,6 @@ static int emsff_init(struct hid_device *hid)
 		return error;
 	}
 
-	emsff->report = report;
 	emsff->report->field[0]->value[0] = 0x01;
 	emsff->report->field[0]->value[1] = 0x00;
 	emsff->report->field[0]->value[2] = 0x00;
@@ -103,34 +97,6 @@ static int emsff_init(struct hid_device *hid)
 	return 0;
 }
 
-static int ems_probe(struct hid_device *hdev, const struct hid_device_id *id)
-{
-	int ret;
-
-	ret = hid_parse(hdev);
-	if (ret) {
-		hid_err(hdev, "parse failed\n");
-		goto err;
-	}
-
-	ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT & ~HID_CONNECT_FF);
-	if (ret) {
-		hid_err(hdev, "hw start failed\n");
-		goto err;
-	}
-
-	ret = emsff_init(hdev);
-	if (ret) {
-		dev_err(&hdev->dev, "force feedback init failed\n");
-		hid_hw_stop(hdev);
-		goto err;
-	}
-
-	return 0;
-err:
-	return ret;
-}
-
 static const struct hid_device_id ems_devices[] = {
 	{ HID_USB_DEVICE(USB_VENDOR_ID_EMS, USB_DEVICE_ID_EMS_TRIO_LINKER_PLUS_II) },
 	{ }
@@ -140,7 +106,7 @@ MODULE_DEVICE_TABLE(hid, ems_devices);
 static struct hid_driver ems_driver = {
 	.name = "hkems",
 	.id_table = ems_devices,
-	.probe = ems_probe,
+	.input_configured = ems_input_configured,
 };
 module_hid_driver(ems_driver);
 

-- 
2.55.0.629.g250fe7f194-goog