Re: [PATCH] PCI: s390: Expose the UID as an arch specific PCI slot attribute

Benjamin Block
2025-09-26T14:27:21Z

> diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h
> index 41f900f693d92522ff729829e446b581977ef3ff..23eed78d9dce72ef466679f31c78aca52ba00f99 100644
> --- a/arch/s390/include/asm/pci.h
> +++ b/arch/s390/include/asm/pci.h
> @@ -207,6 +207,10 @@ extern const struct attribute_group zpci_ident_attr_group;
> &pfip_attr_group, \
> &zpci_ident_attr_group,
>
> +extern const struct attribute_group zpci_slot_attr_group;
> +
> +#define ARCH_PCI_SLOT_GROUPS (&zpci_slot_attr_group)

I don't know the history exactly, but this can't be easily extended like the
other group above `ARCH_PCI_DEV_GROUPS`.

(&zpci_slot_attr_group, \
&zpci_slot_attr_group_b)

Won't compile. The way `ARCH_PCI_DEV_GROUPS` does it, attaching a different
group is just adding a new line.

> diff --git a/arch/s390/pci/pci_sysfs.c b/arch/s390/pci/pci_sysfs.c
> index 0ee0924cfab7e5d22468fb197ee78cac679d8c13..997dff3796094680d9a3f0b6eb27a89fa1ed30b2 100644
> --- a/arch/s390/pci/pci_sysfs.c
> +++ b/arch/s390/pci/pci_sysfs.c
> @@ -178,6 +178,17 @@ static ssize_t index_show(struct device *dev,
> }
> static DEVICE_ATTR_RO(index);
>
> +static ssize_t zpci_uid_slot_show(struct pci_slot *slot, char *buf)
> +{
> + struct zpci_dev *zdev = container_of(slot->hotplug, struct zpci_dev,
> + hotplug_slot);
> +
> + return sysfs_emit(buf, "0x%x\n", zdev->uid);

Do we need a special case for when `uid` is 0? That would imply the uid is
invalid, right? Would we want to return an error in that case (-EINVAL, or
smth)?

Also, do we want to use the same format as in `zpci_setup_bus_resources()`
with the 4 leading 0's (`0x%04x`)?

> +}
> +
> +static struct pci_slot_attribute zpci_slot_attr_uid =
> + __ATTR(uid, 0444, zpci_uid_slot_show, NULL);

__ATTR_RO()?

--
Best Regards, Benjamin Block / Linux on IBM Z Kernel Development
IBM Deutschland Research & Development GmbH / https://www.ibm.com/privacy
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