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

[Ramesh Errabolu <ramesh@linux.ibm.com>]

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@linux.ibm.com>
>> ---
>>   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
>>
>>