linux-kernel - [PATCH] hid-input: Fix devices that return multiple bytes in battery report

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Date:   Fri, 10 Jul 2020 16:19:39 +0100
From:   Grant Likely <grant.likely@...retlab.ca>
To:     unlisted-recipients:; (no To-header on input)
Cc:     linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        Grant Likely <grant.likely@....com>,
        Grant Likely <grant.likely@...retlab.ca>,
        Darren Hart <darren@...art.com>,
        Jiri Kosina <jikos@...nel.org>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        stable@...r.kernel.org
Subject: [PATCH] hid-input: Fix devices that return multiple bytes in battery report

Some devices, particularly the 3DConnexion Spacemouse wireless 3D
controllers, return more than just the battery capacity in the battery
report. The Spacemouse devices return an additional byte with a device
specific field. However, hidinput_query_battery_capacity() only
requests a 2 byte transfer.

When a spacemouse is connected via USB (direct wire, no wireless dongle)
and it returns a 3 byte report instead of the assumed 2 byte battery
report the larger transfer confuses and frightens the USB subsystem
which chooses to ignore the transfer. Then after 2 seconds assume the
device has stopped responding and reset it. This can be reproduced
easily by using a wired connection with a wireless spacemouse. The
Spacemouse will enter a loop of resetting every 2 seconds which can be
observed in dmesg.

This patch solves the problem by increasing the transfer request to 4
bytes instead of 2. The fix isn't particularly elegant, but it is simple
and safe to backport to stable kernels. A further patch will follow to
more elegantly handle battery reports that contain additional data.

Signed-off-by: Grant Likely <grant.likely@...retlab.ca>
Cc: Darren Hart <darren@...art.com>
Cc: Jiri Kosina <jikos@...nel.org>
Cc: Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc: stable@...r.kernel.org
---
 drivers/hid/hid-input.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index dea9cc65bf80..e8641ce677e4 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -350,13 +350,13 @@ static int hidinput_query_battery_capacity(struct hid_device *dev)
 	u8 *buf;
 	int ret;

-	buf = kmalloc(2, GFP_KERNEL);
+	buf = kmalloc(4, GFP_KERNEL);
 	if (!buf)
 		return -ENOMEM;

-	ret = hid_hw_raw_request(dev, dev->battery_report_id, buf, 2,
+	ret = hid_hw_raw_request(dev, dev->battery_report_id, buf, 4,
 				 dev->battery_report_type, HID_REQ_GET_REPORT);
-	if (ret != 2) {
+	if (ret < 2) {
 		kfree(buf);
 		return -ENODATA;
 	}
-- 
2.20.1