Re: Hotplugging ethernet cables.

[Oliver Schinagl <oliver.schinagl@ehv.tass.philips.com>]

What about SATA? sata is hotpluggable. And then, what if we have an 
external hdd rack via USB with a hot plugable sata connector in that. 
(as long as we don't have external sata connectors on laptops/PC's 
sounds reasonable)
Linux-hotplug would notice the USB event, while sata would have to deal 
with the hotplugging of the sata?

Also what about firewire? does linux-hotplugging handle firewire aswell? 
just curious ...

Kay Sievers wrote:

>On Tue, 2005-01-04 at 11:44 -0600, Linas Vepstas wrote:
>  
>
>>A naive question re ethernet hotplug:  what if its iSCSI?
>>
>>On Sun, Jan 02, 2005 at 01:43:32AM +0100, Kay Sievers was heard to remark:
>>    
>>
>>>On Sun, 2005-01-02 at 02:11 +0100, oliver wrote:
>>>      
>>>
>>>>They mention ifplugd and even though this seems to work reasonably, I 
>>>>was wondering why hotplugging doesn't support ethernet hotplugging 
>>>>nativly?
>>>>        
>>>>
>>>Hotplug supports device add and remove, not state changes of hardware.
>>>
>>>      
>>>
>>>>As I understand it the hotplugging daemon responds to events 
>>>>created by several devices, where the ifplugd polls and the device.
>>>>        
>>>>
>>>There is no such daemon involved in the hotplug handling. Hotplug is
>>>driven by more or less stateless scripts invoked by the kernel.
>>>
>>>The network link state changes can be received on a netlink socket from
>>>the kernel. These events are not hotplug events and don't really fit
>>>into the model of linux hotplug.
>>>      
>>>
>>I can imagine  a scenario where Linux has mounted a filesystem that
>>is sitting on an iSCSI disk device.  Thus, in many respects, this is
>>analogous to a USB disk being plugged and unplugged.  I also presume
>>that iSCSI devices need not be just disks, but could be "anything",
>>thus making the situation even more analogous to USB.  
>>    
>>
>
>Sure, it's similar in some aspects, but linux-hotplug is only a device
>"add" or "remove" notification. Every event corresponds to a created or
>removed directory in /sys. There is no such thing for a network link.
>
>If you add/remove the network device you get hotplug events. You don't
>get hotplug events if you press a button of an USB device, which is very
>similar to the network link state change. :)
>
>Some networking applications produce a very high event traffic for state
>changes - like the zebra routing daemon, this is definitely not possible
>to do with the event-by-forked-helper-application-hotplug system. They
>use the netlink socket for good reason. What do you think is the problem
>to get network layer events over netlink? It works nicely this way for a
>long time.
>
>For a application level feature rich example, you may look how HAL is
>collecting all available kernel events and offers a unified interface to
>applications to subscribe to these events:
>  http://cvs.freedesktop.org/*checkout*/hal/hal/doc/spec/hal-spec.html?rev=1.36.2.5
>
>  
>
>>I'm also curious about plans for things like infiniband fabrics,
>>which might be plugged/unplugged in various ways, which the OS might
>>want to know about.  Again, this seems clearly analogous to USB fabrics
>>    
>>
>
>Never seen such a thing. :)
>
>Kay
>
>  
>


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