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 }, {} };