Re: IETP touchpad interrupt failure on Chromebook Edgar

> Date: Mon, 17 Aug 2026 14:50:42 +0000 (UTC)
> From: Gabriel Tourillon <[email protected]>

Can you send me the acpidump output (the files from /var/db/acpi)?

> Hello,
> 
> I'm reporting an I2C touchpad problem on a Google Chromebook Edgar running
> OpenBSD 7.9 amd64.
> 
> Hardware:
> 
> * Google Chromebook Edgar
> * Intel Celeron N3160
> * 4 GB RAM
> * Coreboot / MrChromebox 2606.1
> * OpenBSD 7.9 amd64
> 
> The touchpad is detected, but its interrupt cannot be established:
> 
> dwiic1 at acpi0 I2C6 addr 0xfccdc000/0x1000 irq 37
> iic1 at dwiic1
> ietp0 at iic1 addr 0x15, can't establish interrupt
> 
> The touchpad works with an Artix Linux live system on the same hardware, and
> a USB mouse works normally under OpenBSD.
> 
> I investigated the failure through ietp_attach(), iic_intr_establish(), and
> dwiic_i2c_intr_establish(). The touchpad's ACPI interrupt resource refers to
> the GPNC GPIO controller.
> 
> I found that IETP attempts to establish its interrupt before the GPNC GPIO
> driver has attached. At that point the ACPI node exists, but its GPIO
> information has not been initialized.
> 
> As an experiment, I modified dwiic to defer IETP discovery if its GPIO
> provider has not attached yet. After the GPIO driver attaches, I rescan the
> DWIIC ACPI devices. With this change the ordering becomes:
> 
> chvgpio1 at acpi0 GPNC ...
> ietp0 at iic1 addr 0x15 gpio 18
> 
> and the touchpad works.
> 
> I have attached the experimental patch/workaround. This is intended mainly
> to demonstrate the cause and provide a working test case.
> 
> The modified source tree is available here in the branch chromebook-cb3-431 :
> 
> 
> https://github.com/Grabyy/OpenBSD_src_Chromebook-CB3-431_custom/tree/chromebook-cb3-431
> 
> 
> If you need any additional information or testing, please let me know. I'm
> new to OpenBSD kernel development, so I'm happy to provide anything that
> would be useful.
> 
> Thanks,
> Gabriel.
> 
> [2:application/octet-stream Show Save:dwiic-ietp.patch (2kB)]
>