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Date:   Mon, 8 Nov 2021 14:02:43 +0100
From:   Greg KH <gregkh@linuxfoundation.org>
To:     Shantur Rathore <i@shantur.com>
Cc:     linux-usb@vger.kernel.org
Subject: Re: usb-gadget: dynamic reconfiguration
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On Mon, Nov 08, 2021 at 12:54:37PM +0000, Shantur Rathore wrote:
> Hi all,
> 
> I am trying to figure out if it's possible to reconfigure a usb-gadget
> when it's live.
> The idea is to create a gadget with 1 function - lets say a serial gadget.
> 
> Upon communication with the host, the host could specify (via Serial
> communication) which is the next gadget it needs for example a mass
> storage or ecm and the next gadget can be added to the configuration.
> 
> For now this only works if the gadget is disconnected and reconnected
> to the UDC.
> 
> I want to understand if it is technically possible to add more
> functions to a live config without affecting existing functions.

The USB standard does not allow for this type of thing, sorry.  So this
really isn't anything you could do on the gadget side and expect the
host side to notice it.

thanks,

greg k-h