Re: [PATCH v8 3/3] HID: cp2112: Fwnode Support

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Thu, Mar 02, 2023 at 06:06:06PM +0100, Benjamin Tissoires wrote:
> On Mar 01 2023, Andy Shevchenko wrote:
> > On Tue, Feb 28, 2023 at 01:05:54PM -0600, Daniel Kaehn wrote:

...

> > [1]: https://stackoverflow.com/a/60855157/2511795
> 
> Thanks Andy for your help here, and thanks for that link.
> 
> I am trying to test Danny's patch as I want to use it for my HID CI,
> being an owner of a CP2112 device myself.
> 
> The current setup is using out of the tree patches [2] which are
> implementing a platform i2c-hid support and some manual addition of a
> I2C-HID device on top of it. This works fine but gets busted every now
> and then when the tree sees a change that conflicts with these patches.
> 
> So with Danny's series, I thought I could have an SSDT override to
> declare that very same device instead of patching my kernel before
> testing it.
> 
> Of course, it gets tricky because I need to run that under qemu.
> 
> I am currently stuck at the "sharing the firmware_node from usb with
> HID" step and I'd like to know if you could help me.
> 
> On my laptop, if I plug the CP2112 (without using a USB hub), I can get:
> 
> $> ls -l /sys/bus/hid/devices/0003:10C4:EA90.*
>   lrwxrwxrwx. 1 root root 0 Mar  2 17:02 /sys/bus/hid/devices/0003:10C4:EA90.0079 -> ../../../devices/pci0000:00/0000:00:14.0/usb2/2-9/2-9:1.0/0003:10C4:EA90.0079
> $> ls -l /sys/bus/usb/devices/2-9*/firmware_node
>   lrwxrwxrwx. 1 root root 0 Mar  2 17:03 /sys/bus/usb/devices/2-9:1.0/firmware_node -> ../../../../../LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:15/device:16/device:25
>   lrwxrwxrwx. 1 root root 0 Mar  2 17:02 /sys/bus/usb/devices/2-9/firmware_node -> ../../../../LNXSYSTM:00/LNXSYBUS:00/PNP0A08:00/device:15/device:16/device:25
> 
> So AFAIU the USB device is properly assigned a firmware node. My dsdt
> also shows the "Device (RHUB)" and I guess everything is fine.

Yes, so far so good.

> However, playing with qemu is not so easy.
> 
> I am running qemu with the following arguments (well, almost because I
> have a wrapper script on top of it and I also run the compiled kernel
> from the current tree):
> 
> #> qemu-system-x86_64 -bios /usr/share/edk2/ovmf/OVMF_CODE.fd \
>                       -netdev user,id=hostnet0 \
>                       -device virtio-net-pci,netdev=hostnet0 \
>                       -m 4G \
>                       -enable-kvm \
>                       -cpu host \
>                       -device qemu-xhci -usb \
>                       -device 'usb-host,vendorid=0x10c4,productid=0xea90' \
>                       -cdrom ~/Downloads/Fedora-Workstation-Live-x86_64-37-1.7.iso

Side question, where can I get those blobs from (EDKII and Fedora Live CD)?
I'm using Debian unstable.

> And this is what I get:
> 
> #> ls -l /sys/bus/hid/devices/0003:10C4:EA90.*
>   lrwxrwxrwx 1 root root 0 Mar  2 16:10 /sys/bus/hid/devices/0003:10C4:EA90.0001 -> ../../../devices/pci0000:00/0000:00:06.0/usb2/2-1/2-1:1.0/0003:10C4:EA90.0001
> 
> #> ls -l /sys/bus/usb/devices/2-1*/firmware_node
>   ls: cannot access '/sys/bus/usb/devices/2-1*/firmware_node': No such file or directory
> 
> Looking at the DSDT, I do not see any reference to the USB hub, so I
> wonder if the firmware_node needs to be populated first in the DSDT.

So, where QEMU takes DSDT (ACPI tables in general) from? Can you patch that?
I believe that's the problem in qemu.

> Also note that if I plug the CP2112 over a docking station, I lose the
> firmware_node sysfs entries on the host too.

This seems like a lack of firmware node propagating in the USB hub code in
the Linux kernel.

> Do you think it would be achievable to emulate that over qemu and use a
> mainline kernel without patches?

As long as qemu provides correct DSDT it should work I assume.

> [2] https://gitlab.freedesktop.org/bentiss/gitlab-kernel-ci/-/tree/master/VM

-- 
With Best Regards,
Andy Shevchenko