[PATCH AUTOSEL 6.17-6.6] HID: hid-input: Extend Elan ignore battery quirk to USB

[Sasha Levin <sashal@kernel.org>]

From: "Mario Limonciello (AMD)" <superm1@kernel.org>

[ Upstream commit 534ca75e8e3b713514b3f2da85dab96831cf5b2a ]

USB Elan devices have the same problem as the I2C ones with a fake
battery device showing up.

Reviewed-by: Hans de Goede <hansg@kernel.org>
Reported-by: André Barata <andretiagob@protonmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220722
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

LLM Generated explanations, may be completely bogus:

## Comprehensive Analysis

### 1. Commit Message Analysis
The commit "HID: hid-input: Extend Elan ignore battery quirk to USB"
addresses a specific hardware compatibility issue where Elan USB
touchscreens incorrectly report a battery device to the OS.
- **Problem:** Users see a non-existent or "fake" battery in their
  system tray/power settings, which can cause confusion and interfere
  with power management logic.
- **Context:** The message notes that "USB Elan devices have the same
  problem as the I2C ones," referencing a known issue.
- **References:** It links to a specific bug report (Bugzilla #220722)
  and has a `Reviewed-by` tag from the subsystem maintainer (Hans de
  Goede).

### 2. Deep Code Research
- **Code Change:** The patch modifies `drivers/hid/hid-input.c` by
  adding a single line to the `hid_battery_quirks` table:
  ```c
  { HID_USB_DEVICE(USB_VENDOR_ID_ELAN, HID_ANY_ID),
  HID_BATTERY_QUIRK_IGNORE },
  ```
- **Historical Context:** This change mirrors commit `bcc31692a1d1e`
  (August 2024), which applied the same `HID_ANY_ID` catch-all quirk for
  **I2C** Elan devices. That previous commit was successfully backported
  to stable trees.
- **Mechanism:** The `hid-input` driver checks connected devices against
  the `hid_battery_quirks` table. When a match is found with
  `HID_BATTERY_QUIRK_IGNORE`, the function `hidinput_setup_battery()`
  returns early, preventing the creation of the bogus power supply
  device in `/sys/class/power_supply/`.
- **Precedent:** The file already contains specific quirks for some Elan
  USB devices (e.g., ASUS UX550). This commit generalizes the fix to all
  Elan USB devices, cleaning up the approach.

### 3. Stable Kernel Rules Assessment
- **Fixes a Real Bug:** Yes. It prevents the kernel from exposing false
  hardware information to userspace.
- **Quirks and Workarounds Exception:** This falls strictly under the
  "QUIRKS and WORKAROUNDS" exception category allowed in stable kernels
  ("Hardware-specific quirks for broken/buggy devices").
- **Small and Contained:** The change is surgical—one line of code added
  to a static array. It has no logic complexity or dependencies.
- **Regression Risk:** Extremely Low. It simply disables battery
  reporting for a specific vendor's input devices. Since the battery
  reporting is known to be broken (always 0% or 1%), ignoring it
  restores correct behavior.
- **Mainline Status:** Reviewed by maintainers and tested by the
  reporter.

### 4. Conclusion
This commit is an ideal candidate for backporting. It is a one-line
hardware quirk that fixes a user-visible annoyance (fake battery
devices). It follows a pattern already established and backported for
I2C devices, ensuring consistency across different bus types for the
same hardware vendor.

**YES**

 drivers/hid/hid-input.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/hid/hid-input.c b/drivers/hid/hid-input.c
index 2c743e35c1d33..bc7de9ef45ecd 100644
--- a/drivers/hid/hid-input.c
+++ b/drivers/hid/hid-input.c
@@ -386,10 +386,11 @@ static const struct hid_device_id hid_battery_quirks[] = {
 	{ HID_I2C_DEVICE(USB_VENDOR_ID_ELAN, I2C_DEVICE_ID_CHROMEBOOK_TROGDOR_POMPOM),
 	  HID_BATTERY_QUIRK_AVOID_QUERY },
 	/*
-	 * Elan I2C-HID touchscreens seem to all report a non present battery,
-	 * set HID_BATTERY_QUIRK_IGNORE for all Elan I2C-HID devices.
+	 * Elan HID touchscreens seem to all report a non present battery,
+	 * set HID_BATTERY_QUIRK_IGNORE for all Elan I2C and USB HID devices.
 	 */
 	{ HID_I2C_DEVICE(USB_VENDOR_ID_ELAN, HID_ANY_ID), HID_BATTERY_QUIRK_IGNORE },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ELAN, HID_ANY_ID), HID_BATTERY_QUIRK_IGNORE },
 	{}
 };
 
-- 
2.51.0