Messages in this thread | | | From | Sean Anderson <> | Subject | Re: [RFC net-next PATCH 05/16] net: phylink: Automatically attach PCS devices | Date | Tue, 5 Oct 2021 12:42:53 -0400 |
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On 10/5/21 5:48 AM, Russell King (Oracle) wrote: > On Mon, Oct 04, 2021 at 03:15:16PM -0400, Sean Anderson wrote: >> This adds support for automatically attaching PCS devices when creating >> a phylink. To do this, drivers must first register with >> phylink_register_pcs. After that, new phylinks will attach the PCS >> device specified by the "pcs" property. >> >> At the moment there is no support for specifying the interface used to >> talk to the PCS. The MAC driver is expected to know how to talk to the >> PCS. This is not a change, but it is perhaps an area for improvement. >> >> I believe this is mostly correct with regard to registering/ >> unregistering. However I am not too familiar with the guts of Linux's >> device subsystem. It is possible (likely, even) that the current system >> is insufficient to prevent removing PCS devices which are still in-use. >> I would really appreciate any feedback, or suggestions of subsystems to >> use as reference. In particular: do I need to manually create device >> links? Should I instead add an entry to of_supplier_bindings? Do I need >> a call to try_module_get? > > I think this is an area that needs to be thought about carefully. > Things are not trivial here. > > The first mistake I see below is the use of device links. pl->dev is > the "struct device" embedded within "struct net_device". This doesn't > have a driver associated with it, and so using device links is likely > ineffectual.
So what can the device in net_device be used for?
> Even with the right device, I think careful thought is needed - we have > network drivers where one "struct device" contains multiple network > interfaces. Should the removal of a PCS from one network interface take > out all of them?
Well, it's more of the other way around. We need to prevent removing the PCS while it is still in-use.
> Alternatively, could we instead use phylink to "unplug" the PCS and > mark the link down - would that be a better approach than trying to > use device links?
So here, I think the logic should be: allow phylink to "unplug" the PCS only when the link is down.
--Sean
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