linux-kernel - 答复: 答复: [External Mail]Re: The zero power level of the HID device in kernel 6.12 is not reported from the kernel to the upper layer.

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Message-ID: <aada0917f31641c19ba7c48e3c6d3c53@xiaomi.com>
Date: Fri, 26 Sep 2025 12:03:19 +0000
From: 卢国宏 <luguohong@...omi.com>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>
CC: José Expósito <jose.exposito89@...il.com>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"jikos@...nel.org" <jikos@...nel.org>, "bentiss@...nel.org"
	<bentiss@...nel.org>, 李鹏 <lipeng43@...omi.com>,
	Fei1 Jiang 蒋飞 <jiangfei1@...omi.com>,
	宋密密 <songmimi@...omi.com>, 卢国宏
	<luguohong@...omi.com>
Subject: 答复: 答复: [External Mail]Re: The zero power level of the HID device in kernel 6.12 is not reported from the kernel to the upper layer.


Hi Dmitry,
After testing, we found that your proposed method can solve our problem. Please help merge this method into the Linux kernel as soon as possible! Please remember to send us the relevant information of the merged git so that we can contact Google and merge their Android GKI as well. Our project is looking forward to using this feature. Thank you very much!

________________________________________
发件人: Dmitry Torokhov <dmitry.torokhov@...il.com>
发送时间: 2025年9月25日 12:26
收件人: 卢国宏
抄送: José Expósito; linux-input@...r.kernel.org; linux-kernel@...r.kernel.org; jikos@...nel.org; bentiss@...nel.org; 李鹏; Fei1 Jiang 蒋飞; 宋密密
主题: Re: 答复: [External Mail]Re: The zero power level of the HID device in kernel 6.12 is not reported from the kernel to the upper layer.

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On Mon, Sep 22, 2025 at 09:29:20AM +0000, 卢国宏 wrote:
>
> What kind of action are we talking about? Section 31 of the HID
> specification defines events for "Smart Battery" ("To comply with the
> Smart Battery Specification, the Battery System must support the
> functions defined in the Battery and Charger usage tables. For details,
> see Section 4.2, “Battery System Page (x85).”) and is typically used for
> "battery pack for cellular phones (principal source), the battery
> pack(s) for notebook computers (auxiliary source), and the sealed
> batteries in uninterruptible power supplies (auxiliary source)."
>
> Is your use case main battery or battery in a stylus or some other
> peripheral?
>
>
> --->>>
> What we are discussing is the code implementation of Section 31 of the
> HID protocol: 31 Battery System Page (0x85). Our scenario is: an
> Android phone is connected to a handle via USB. The handle is a HID
> device with a battery. The power of the battery in the handle is sent
> to the bottom layer (kernel) of the phone via USB. The bottom layer of
> the phone then reports this power to the upper layer of Android
> through the HID driver.

I see. I guess we can try only filtering out 0 reports for the
digitizers, leaving other devices with batteries alone. Something like
this:


diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index ff1784b5c2a4..ba3f6655af9e 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -595,14 +595,18 @@ static void hidinput_cleanup_battery(struct hid_device *dev)
        dev->battery = NULL;
 }

-static void hidinput_update_battery(struct hid_device *dev, int value)
+static void hidinput_update_battery(struct hid_device *dev,
+                                   unsigned int usage, int value)
 {
        int capacity;

        if (!dev->battery)
                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);
@@ -1518,7 +1522,7 @@ void hidinput_hid_event(struct hid_device *hid, struct hid_field *field, struct
                bool handled = hidinput_set_battery_charge_status(hid, usage->hid, value);

                if (!handled)
-                       hidinput_update_battery(hid, value);
+                       hidinput_update_battery(hid, usage->hid, value);

                return;
        }


Thanks.

--
Dmitry
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