> It seems the _UID() in case of matching is present and not empty ("0" vs. "").
> The question is why we have no UID is not there?
Looking at the IOMMU IVRS spec:
```
Unique ID Format
0= UID not present
1= UID is an integer
2= UID is a character string
```
So it's optional. I added a bit of logging here:
https://source.chromium.org/chromiumos/chromiumos/codesearch/+/master:src/third_party/kernel/v5.4/drivers/iommu/amd_iommu_init.c;l=1353
```
[ 11.730159] AMD-Vi: UID is not present.
[ 11.734422] AMD-Vi: DEV_ACPI_HID(AMDI0040[]) devid: 00:13.1
[ 11.740913] AMD-Vi: ivrs, add hid:AMDI0040, uid:, rdevid:152
```
> The quick fix looks like
>
> - if (acpi_dev_hid_uid_match(adev, p->hid, p->uid)) {
> + if (acpi_dev_hid_uid_match(adev, p->hid, *p->uid ? p->uid : NULL)) {
>
> Can you test it?
>
Your patch works and fixes the matching. Thanks!
