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From:   Dmitry Torokhov <dmitry.torokhov@gmail.com>
To:     Jiri Kosina <jikos@kernel.org>,
        Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc:     linux-input@vger.kernel.org, linux-kernel@vger.kernel.org,
        Stephen Boyd <swboyd@chromium.org>
Subject: [PATCH v2 1/2] HID: split apart hid_device_probe to make logic more apparent
Date:   Tue, 23 May 2023 14:04:31 -0700
Message-ID: <20230523-hid-devres-v2-1-5220211a428c@gmail.com>
In-Reply-To: <20230523-hid-devres-v2-0-5220211a428c@gmail.com>
References: <20230523-hid-devres-v2-0-5220211a428c@gmail.com>
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Precedence: bulk

hid_device_probe() has a complex flow and locks and unlocks a mutex.
Move the most of the logic into __hid_device_probe() and
hid_check_device_match() and leave the locking in hid_device_probe()
which makes the code more clear.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
 drivers/hid/hid-core.c | 101 ++++++++++++++++++++++++++-----------------------
 1 file changed, 54 insertions(+), 47 deletions(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 22623eb4f72f..1f0bb2784bfc 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -2587,64 +2587,71 @@ bool hid_compare_device_paths(struct hid_device *hdev_a,
 }
 EXPORT_SYMBOL_GPL(hid_compare_device_paths);
 
+static bool hid_check_device_match(struct hid_device *hdev,
+				   struct hid_driver *hdrv,
+				   const struct hid_device_id **id)
+{
+	*id = hid_match_device(hdev, hdrv);
+	if (!*id)
+		return -ENODEV;
+
+	if (hdrv->match)
+		return hdrv->match(hdev, hid_ignore_special_drivers);
+
+	/*
+	 * hid-generic implements .match(), so we must be dealing with a
+	 * different HID driver here, and can simply check if
+	 * hid_ignore_special_drivers is set or not.
+	 */
+	return !hid_ignore_special_drivers;
+}
+
+static int __hid_device_probe(struct hid_device *hdev, struct hid_driver *hdrv)
+{
+	const struct hid_device_id *id;
+	int ret;
+
+	if (!hid_check_device_match(hdev, hdrv, &id))
+		return -ENODEV;
+
+	/* reset the quirks that has been previously set */
+	hdev->quirks = hid_lookup_quirk(hdev);
+	hdev->driver = hdrv;
+
+	if (hdrv->probe) {
+		ret = hdrv->probe(hdev, id);
+	} else { /* default probe */
+		ret = hid_open_report(hdev);
+		if (!ret)
+			ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
+	}
+
+	if (ret) {
+		hid_close_report(hdev);
+		hdev->driver = NULL;
+	}
+
+	return ret;
+}
+
 static int hid_device_probe(struct device *dev)
 {
-	struct hid_driver *hdrv = to_hid_driver(dev->driver);
 	struct hid_device *hdev = to_hid_device(dev);
-	const struct hid_device_id *id;
+	struct hid_driver *hdrv = to_hid_driver(dev->driver);
 	int ret = 0;
 
-	if (down_interruptible(&hdev->driver_input_lock)) {
-		ret = -EINTR;
-		goto end;
-	}
-	hdev->io_started = false;
+	if (down_interruptible(&hdev->driver_input_lock))
+		return -EINTR;
 
+	hdev->io_started = false;
 	clear_bit(ffs(HID_STAT_REPROBED), &hdev->status);
 
-	if (!hdev->driver) {
-		id = hid_match_device(hdev, hdrv);
-		if (id == NULL) {
-			ret = -ENODEV;
-			goto unlock;
-		}
+	if (!hdev->driver)
+		ret = __hid_device_probe(hdev, hdrv);
 
-		if (hdrv->match) {
-			if (!hdrv->match(hdev, hid_ignore_special_drivers)) {
-				ret = -ENODEV;
-				goto unlock;
-			}
-		} else {
-			/*
-			 * hid-generic implements .match(), so if
-			 * hid_ignore_special_drivers is set, we can safely
-			 * return.
-			 */
-			if (hid_ignore_special_drivers) {
-				ret = -ENODEV;
-				goto unlock;
-			}
-		}
-
-		/* reset the quirks that has been previously set */
-		hdev->quirks = hid_lookup_quirk(hdev);
-		hdev->driver = hdrv;
-		if (hdrv->probe) {
-			ret = hdrv->probe(hdev, id);
-		} else { /* default probe */
-			ret = hid_open_report(hdev);
-			if (!ret)
-				ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
-		}
-		if (ret) {
-			hid_close_report(hdev);
-			hdev->driver = NULL;
-		}
-	}
-unlock:
 	if (!hdev->io_started)
 		up(&hdev->driver_input_lock);
-end:
+
 	return ret;
 }
 

-- 
2.40.1.698.g37aff9b760-goog