Re: [PATCH v5 13/18] pci: introduce pci_find_the_only_child()

[Michael S. Tsirkin]

On Thu, Mar 02, 2023 at 11:45:00AM +0300, Vladimir Sementsov-Ogievskiy wrote:
> On 02.03.23 11:37, Michael S. Tsirkin wrote:
> > On Thu, Mar 02, 2023 at 11:28:44AM +0300, Vladimir Sementsov-Ogievskiy 
> > wrote:
> > > On 02.03.23 00:09, Michael S. Tsirkin wrote:
> > > > On Thu, Feb 16, 2023 at 09:03:51PM +0300, Vladimir Sementsov-Ogievskiy 
> > > > wrote:
> > > > > To be used in further patch to identify the device hot-plugged into
> > > > > pcie-root-port.
> > > > > 
> > > > > Signed-off-by: Vladimir Sementsov-Ogievskiy<vsementsov@yandex-team.ru>
> > > > > Reviewed-by: Anton Kuchin<antonkuchin@yandex-team.ru>
> > > > Wait a second does this work for multifunction devices correctly?
> > > > 
> > > 
> > > I thought about that and I'm just lost:)
> > > 
> > > Could several (multifunction?) devices be plugged into one pcie-root-port 
> > > device?
> > 
> > One device per port but one multifunction device is represented as multiple 
> > PCIDevice structures.
> 
> So, it should be OK to send _one_ event for that multifunction device, and 
> the code is shpc_reset() is OK, but reporting "Several child devices found" 
> is bad idea?

I don't know about your new event, we are discussing it separately.
yes all functions are removed together normally on real hardware.

> So, if I change the logic from pci_find_the_only_child() to 
> pci_find_first_child() is it OK?

Yes though I don't like this name either - need to make it clear that
multifunction is ok, multiple unrelated devices aren't.


> > 
> > > Same question for SHPC slots. For example, shpc_free_devices_in_slot() 
> > > looks like we can have several devices in one slot..
> > > On the other hand, in shpc_reset() we have construction 
> > > shpc->sec_bus->devices[PCI_DEVFN(SHPC_IDX_TO_PCI(i), 0)] to access the 
> > > device in slot. The only one device.
> > > 
> > > -- 
> > > Best regards,
> > > Vladimir
> > 
> > Same thing.
> > 
> > ... and let's not get started about sriov and ari ...
> > 
> 
> -- 
> Best regards,
> Vladimir