linux-kernel - [PATCH v2] HID: hid-input: only ignore 0 battery events for digitizers

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Message-ID: <c5b52grvciabpcgavhjqximqqq6fczowgvmckke6aflq72mzyv@gzzkyt25xygc>
Date: Tue, 14 Oct 2025 21:28:44 -0700
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Jiri Kosina <jikos@...nel.org>, 
	Benjamin Tissoires <bentiss@...nel.org>
Cc: 卢国宏 <luguohong@...omi.com>, kenalba@...gle.com, 
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] HID: hid-input: only ignore 0 battery events for
 digitizers

Commit 581c4484769e ("HID: input: map digitizer battery usage") added
handling of battery events for digitizers (typically for batteries
presented in stylii). Digitizers typically report correct battery levels
only when stylus is actively touching the surface, and in other cases
they may report battery level of 0. To avoid confusing consumers of the
battery information the code was added to filer out reports with 0
battery levels.

However there exist other kinds of devices that may legitimately report
0 battery levels. Fix this by filtering out 0-level reports only for
digitizer usages, and continue reporting them for other kinds of devices
(Smart Batteries, etc).

Reported-by: 卢国宏 <luguohong@...omi.com>
Fixes: 581c4484769e ("HID: input: map digitizer battery usage")
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
---

v2: rebased on top of linux-next, dropped Tested-by: tag

 drivers/hid/hid-input.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index 5d7532d79d21..e56e7de53279 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -635,7 +635,10 @@ static void hidinput_update_battery(struct hid_device *dev, unsigned int usage,
 		return;
 	}

-	if (value == 0 || value < dev->battery_min || value > dev->battery_max)
+	if ((usage & HID_USAGE_PAGE) == HID_UP_DIGITIZER && value == 0)
+		return;
+
+	if (value < dev->battery_min || value > dev->battery_max)
 		return;

 	capacity = hidinput_scale_battery_capacity(dev, value);
-- 
2.51.0.858.gf9c4a03a3a-goog

-- 
Dmitry