netdev - Re: [PATCH v8 3/8] thunderbolt: Communication with the ICM (firmware)

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Date:   Tue, 20 Dec 2016 10:09:16 +0200
From:   Mika Westerberg <mika.westerberg@...el.com>
To:     Mario.Limonciello@...l.com
Cc:     luto@...nel.org, amir.jer.levy@...el.com,
        gregkh@...uxfoundation.org, andreas.noever@...il.com,
        bhelgaas@...gle.com, corbet@....net, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, netdev@...r.kernel.org,
        linux-doc@...r.kernel.org, thunderbolt-linux@...el.com,
        tomas.winkler@...el.com, xiong.y.zhang@...el.com
Subject: Re: [PATCH v8 3/8] thunderbolt: Communication with the ICM (firmware)

On Mon, Dec 19, 2016 at 05:21:39PM +0000, Mario.Limonciello@...l.com wrote:
> Dell - Internal Use - Confidential  
> 
> > 
> > There is small problem, though. On non-Apple systems the host controller only
> > appears when something is connected to thunderbolt ports. So the char device
> > would not be there all the time. However, I think we can still notify the
> > userspace by sending an extra uevent when we detect there is a PCIe device or
> > inter-domain connection plugged in.
> > 
> 
> Why couldn't you just create it the first time a device is plugged into a Thunderbolt
> port and leave it until the module is cleaned up?  If the host controller goes to sleep
> an event could be sent to the daemon to let it know it disappeared and not to expect
> data on the char device for now, but leave the node around. 

We don't do that for USB memory sticks (or any other removable media)
either - once you disconnect the device the nodes are also removed. I
suppose same goes with USB network adapters, which is closest to
thunderbolt networking I can think of.