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

[Ramesh Errabolu]

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. Secondly there is no uevent 
attribute in slot-id directory to submit requests to raise a uevent. 
This  patch fills that gap

> > The patch was validated by manually triggering PCI slot 'add'
> > uevents through the slot’s 'uevent' sysfs file and confirming
> > that udev received and processed those events. The following
> > command raises an 'add' uevent for a specific PCI slot:
> >
> >      $ echo "add $(uuidgen)" | sudo tee   \
> >                  /sys/bus/pci/slots/<slot-id>/uevent
> >
> > Signed-off-by: Ramesh Errabolu <ramesh@xxxxxxxxxxxxx>
> > ---
> >   drivers/pci/slot.c | 12 ++++++++++++
> >   1 file changed, 12 insertions(+)
> >
> > diff --git a/drivers/pci/slot.c b/drivers/pci/slot.c
> > index 787311614e5b..cbc7cf6ab7ad 100644
> > --- a/drivers/pci/slot.c
> > +++ b/drivers/pci/slot.c
> > @@ -63,6 +63,15 @@ static ssize_t cur_speed_read_file(struct pci_slot *slot, char *buf)
> >   	return bus_speed_read(slot->bus->cur_bus_speed, buf);
> >   }
> >   
> > +static ssize_t uevent_write_file(struct pci_slot *slot,
> > +				 const char *buf, size_t len)
> > +{
> > +	int rc;
> > +
> > +	rc = kobject_synth_uevent(&slot->kobj, buf, len);
> > +	return rc ? rc : len;
> > +}
> > +
> >   static void pci_slot_release(struct kobject *kobj)
> >   {
> >   	struct pci_dev *dev;
> > @@ -89,11 +98,14 @@ static struct pci_slot_attribute pci_slot_attr_max_speed =
> >   	__ATTR(max_bus_speed, S_IRUGO, max_speed_read_file, NULL);
> >   static struct pci_slot_attribute pci_slot_attr_cur_speed =
> >   	__ATTR(cur_bus_speed, S_IRUGO, cur_speed_read_file, NULL);
> > +static struct pci_slot_attribute pci_slot_attr_uevent =
> > +	__ATTR(uevent, S_IWUSR, NULL, uevent_write_file);
> >   
> >   static struct attribute *pci_slot_default_attrs[] = {
> >   	&pci_slot_attr_address.attr,
> >   	&pci_slot_attr_max_speed.attr,
> >   	&pci_slot_attr_cur_speed.attr,
> > +	&pci_slot_attr_uevent.attr,
> >   	NULL,
> >   };
> >   ATTRIBUTE_GROUPS(pci_slot_default);
> > --
> > 2.43.0