Re: [PATCH v1] PCI: Add write-only 'uevent' sysfs attribute for PCI slots

[Leon Romanovsky <leon@kernel.org>]

On Fri, Feb 27, 2026 at 12:23:03PM +0100, Peter Oberparleiter wrote:
> On 2/26/2026 7:39 PM, Leon Romanovsky wrote:
> > On Thu, Feb 26, 2026 at 11:53:32AM -0600, Ramesh Errabolu wrote:
> >> On 2/26/2026 2:34 AM, Leon Romanovsky wrote:
> >>> On Wed, Feb 25, 2026 at 09:08:15AM -0600, Ramesh Errabolu wrote:
> >>>> Add a new write-only 'uevent' attribute to PCI slot sysfs
> >>>> entries. This provides a mechanism for userspace to explicitly
> >>>> synthesize PCI slot uevents when needed.
> >>>>
> >>>> For cold-plugged PCI devices, slots may be created before
> >>>> udev is ready to receive events, causing the initial 'add'
> >>>> uevents to be missed. As a result, slot specific udev
> >>>> rules that define naming, permissions, and related policies,
> >>>> are not applied at boot. Allowing userspace to resynthesize
> >>>> the 'add' uevent ensures these rules are processed correctly.
> >>> This patch sounds like a hack to me. AFAIK, "udevadm trigger"
> >>> performs exactly that.
> >>>
> >>> Thanks
> >>
> >> AFAIK, PCI slots do not yet raise a uevent. 
> 
> That is only partially true. PCI slots are represented in sysfs by a
> kobject (pci_slot.kobj) and pci_hotplug_core generates uevents for these
> kobjects during pci_hp_add() [1].
> 
> Here is an example for these uevents:
> 
> KERNEL[62021.190266] add      /bus/pci/slots/000018d0 (slots)
> ACTION=add
> DEVPATH=/bus/pci/slots/000018d0
> SUBSYSTEM=slots
> SEQNUM=1638
> 
> KERNEL[62032.304390] remove   /bus/pci/slots/000018d0 (slots)
> ACTION=remove
> DEVPATH=/bus/pci/slots/000018d0
> SUBSYSTEM=slots
> SEQNUM=1682
> 
> On s390 there is a use case for reacting to these events via udev rules,
> namely to persistently apply a user-specified, per-slot power state.

But the component that issues the uevent should create this file.
In your example, it is the hotplug code that must provide a writable
file, isn't it?

Thanks