linux-kernel - [PATCH v3 1/3] HID: i2c-hid: Rely on HID descriptor fetch to probe

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Date: Sat, 27 Apr 2024 00:47:07 +0200
From: Kenny Levinsen <kl@...wtf>
To: Jiri Kosina <jikos@...nel.org>,
	Dmitry Torokhov <dtor@...omium.org>,
	Benjamin Tissoires <benjamin.tissoires@...hat.com>,
	Douglas Anderson <dianders@...omium.org>,
	Hans de Goede <hdegoede@...hat.com>,
	Maxime Ripard <mripard@...nel.org>,
	Kai-Heng Feng <kai.heng.feng@...onical.com>,
	Johan Hovold <johan+linaro@...nel.org>,
	linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Radoslaw Biernacki <rad@...omium.org>,
	Lukasz Majczak <lma@...omium.org>
Cc: Kenny Levinsen <kl@...wtf>
Subject: [PATCH v3 1/3] HID: i2c-hid: Rely on HID descriptor fetch to probe

To avoid error messages when a device is not present, b3a81b6c4fc6 added
an initial bus probe using a dummy i2c_smbus_read_byte() call.

Without this probe, i2c_hid_fetch_hid_descriptor() will fail internally
on a bus error and log. Treat the bus error as a missing device and
remove the error log so we can do away with the probe.

Tested-by: Lukasz Majczak <lma@...omium.org>
Reviewed-by: Lukasz Majczak <lma@...omium.org>
Signed-off-by: Kenny Levinsen <kl@...wtf>
---
 drivers/hid/i2c-hid/i2c-hid-core.c | 21 ++++++---------------
 1 file changed, 6 insertions(+), 15 deletions(-)

diff --git a/drivers/hid/i2c-hid/i2c-hid-core.c b/drivers/hid/i2c-hid/i2c-hid-core.c
index d965382196c6..6ffa43d245b4 100644
--- a/drivers/hid/i2c-hid/i2c-hid-core.c
+++ b/drivers/hid/i2c-hid/i2c-hid-core.c
@@ -872,12 +872,11 @@ static int i2c_hid_fetch_hid_descriptor(struct i2c_hid *ihid)
 					      ihid->wHIDDescRegister,
 					      &ihid->hdesc,
 					      sizeof(ihid->hdesc));
-		if (error) {
-			dev_err(&ihid->client->dev,
-				"failed to fetch HID descriptor: %d\n",
-				error);
-			return -ENODEV;
-		}
+
+		/* The i2c drivers are a bit inconsistent with their error
+		 * codes, so treat everything as -ENXIO for now. */
+		if (error)
+			return -ENXIO;
 	}
 
 	/* Validate the length of HID descriptor, the 4 first bytes:
@@ -992,17 +991,9 @@ static int __i2c_hid_core_probe(struct i2c_hid *ihid)
 	struct hid_device *hid = ihid->hid;
 	int ret;
 
-	/* Make sure there is something at this address */
-	ret = i2c_smbus_read_byte(client);
-	if (ret < 0) {
-		i2c_hid_dbg(ihid, "nothing at this address: %d\n", ret);
-		return -ENXIO;
-	}
-
 	ret = i2c_hid_fetch_hid_descriptor(ihid);
 	if (ret < 0) {
-		dev_err(&client->dev,
-			"Failed to fetch the HID Descriptor\n");
+		i2c_hid_dbg(ihid, "failed to fetch HID descriptor: %d\n", ret);
 		return ret;
 	}
 
-- 
2.44.0