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

[Leon Romanovsky]

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

> 
> 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
> 
>