linux-kernel - [PATCH 1/2] HID: core: factor out hid_set

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Message-Id: <20250821-bpf-rescan-v1-1-08f9e2bc01bb@kernel.org>
Date: Thu, 21 Aug 2025 16:38:13 +0200
From: Benjamin Tissoires <bentiss@...nel.org>
To: Jiri Kosina <jikos@...nel.org>, 
 Peter Hutterer <peter.hutterer@...-t.net>
Cc: linux-input@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Benjamin Tissoires <bentiss@...nel.org>
Subject: [PATCH 1/2] HID: core: factor out hid_set_group()

When we load a bpf, we can change the report descriptor. However, the
current implementation doesn't change the group meaning that we can not
rebind a device from hid-generic to hid-multitouch.

This is a preparatory patch to force a rescan of the device after the
bpf has been loaded.

Signed-off-by: Benjamin Tissoires <bentiss@...nel.org>
---
 drivers/hid/hid-core.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 5419a6c10907e307df08c3b44e2b3a147f1b154a..cf68fdffe0581eefb29a9d691f4acfc8f0d175d5 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -2708,6 +2708,20 @@ static bool hid_check_device_match(struct hid_device *hdev,
 	return !hid_ignore_special_drivers && !(hdev->quirks & HID_QUIRK_IGNORE_SPECIAL_DRIVER);
 }
 
+static void hid_set_group(struct hid_device *hdev)
+{
+	int ret;
+
+	if (hid_ignore_special_drivers) {
+		hdev->group = HID_GROUP_GENERIC;
+	} else if (!hdev->group &&
+		   !(hdev->quirks & HID_QUIRK_HAVE_SPECIAL_DRIVER)) {
+		ret = hid_scan_report(hdev);
+		if (ret)
+			hid_warn(hdev, "bad device descriptor (%d)\n", ret);
+	}
+}
+
 static int __hid_device_probe(struct hid_device *hdev, struct hid_driver *hdrv)
 {
 	const struct hid_device_id *id;
@@ -2903,14 +2917,7 @@ int hid_add_device(struct hid_device *hdev)
 	/*
 	 * Scan generic devices for group information
 	 */
-	if (hid_ignore_special_drivers) {
-		hdev->group = HID_GROUP_GENERIC;
-	} else if (!hdev->group &&
-		   !(hdev->quirks & HID_QUIRK_HAVE_SPECIAL_DRIVER)) {
-		ret = hid_scan_report(hdev);
-		if (ret)
-			hid_warn(hdev, "bad device descriptor (%d)\n", ret);
-	}
+	hid_set_group(hdev);
 
 	hdev->id = atomic_inc_return(&id);
 

-- 
2.50.1