Re: Serdev: USB device and sysdev probing ala i2c

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On Thu, May 24, 2018 at 07:38:41PM +0200, Ricardo Ribalda Delgado wrote:

> On Thu, May 24, 2018 at 6:49 PM Rob Herring <robh@xxxxxxxxxx> wrote:

> > The fundamental problem here is you need a parent device node to apply
> > a DT overlay to and a USB device hotplugged has no DT device node. The
> > system you are running on may not even have a DT (like a PC). If you
> > have an overlay of the downstream devices, they have to be a child of
> > something for the overlay to apply to. We could just create virtual
> > device nodes for the purposes of applying overlays to. Another option
> > would be allowing multiple DTs. Then you aren't even using overlays
> > (what's the point of an overlay when a system has no real DT to begin
> > with). That also would mean they are completely independent from any
> > real DT or other instances (you may want to plug in multiple of the
> > same device).
> 
> In my usecase the DT is way too overkilled. The previously mentioned
> echo tty > /sys/bus/serio/devices/serio0/unregister
> echo hci_nokia > /sys/bus/serio/devices/serio0/new_device
> 
> would be the most convenient way to use/experiment with serio.

Note is serio is something different from serdev (whose bus type is
named "serial").

> I am not taking into consideration hot pluggable devices. I am thinking
> about a use case where the usb2serial is soldered in the board.

For static setups like that, my USB serial device-tree patches would
solve your problem if only you were using device tree. ;)

But there's currently no way to register a serdev client from user
space, and adding support for that is not going to be trivial.

Johan
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