Public bug reported:
**Title:** Regression: ELAN0511 I2C Touchpad not detected in kernel
7.0.0-28 on Acer Aspire A715-71G
## Summary
After upgrading from Linux kernel **6.17.0-40-generic** to
**7.0.0-28-generic**, the built-in ELAN touchpad completely disappears
from the system.
The touchpad works correctly with kernel **6.17.0-40**, but is not
detected at all with **7.0.0-28**.
The issue appears to be a kernel regression.
---
## System
**Distribution**
Linux Mint 22.2 (Zara)
Based on Ubuntu Noble
**Kernel working**
6.17.0-40-generic
**Kernel failing**
7.0.0-28-generic
**Computer**
Acer Aspire A715-71G
BIOS Version: V1.10
BIOS Date: 2017-08-22
---
## Expected behaviour
The internal ELAN touchpad should be detected and usable.
---
## Actual behaviour
The touchpad is completely absent.
No input device is created.
No `/dev/input/event*` corresponding to the touchpad exists.
---
## Investigation
### ACPI devices
Two ELAN devices are present.
ELAN0511:00
```
path = \_SB_.PCI0.LPCB.PS2M
status = 0
```
Disabled.
ELAN0511:01
```
path = \_SB_.PCI0.I2C1.TPAD
status = 15
cid = PNP0C50
hid = ELAN0511
```
This is the actual touchpad.
---
### Drivers
The following modules are loaded:
```
i2c_hid
i2c_hid_acpi
hid
hid_generic
```
The module loads successfully.
No errors are reported.
---
### dmesg
Kernel 7.0.0-28 produces no messages related to:
```
i2c-hid
ELAN0511
```
Only the ELAN fingerprint reader appears.
---
### Input devices
`/proc/bus/input/devices` contains:
* keyboard
* USB mouse
* Acer hotkeys
No ELAN touchpad appears.
---
### PS/2 investigation
`psmouse` loads correctly.
The kernel reports:
```
i8042: PS/2 appears to have AUX port disabled
```
However the touchpad is not connected through PS/2.
ACPI identifies it as
```
\_SB_.PCI0.I2C1.TPAD
```
---
### Kernel parameters tested
The following parameters were tested without success:
```
i8042.nopnp
acpi_osi=! acpi_osi="Windows 2020"
```
---
## Workaround
Booting with kernel
```
6.17.0-40-generic
```
restores full touchpad functionality.
---
## Conclusion
This appears to be a regression introduced between kernels
```
6.17.0-40
```
and
```
7.0.0-28
```
where the ELAN0511 I2C touchpad is no longer bound to the i2c-hid
driver.
The ACPI device is present and enabled (`status=15`), but the kernel
never instantiates the HID-over-I2C device.
Any help identifying the offending commit would be appreciated.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2162766
Title:
Regression: ELAN0511 I2C Touchpad not detected in kernel 7.0.0-28 on
Acer Aspire A715-71G
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