Attaching ugen to all usb devices

[Bernd Walter]

On Mon, Dec 25, 2006 at 11:52:00PM +0100, Hans Petter Selasky wrote:
> On Monday 25 December 2006 21:38, M. Warner Losh wrote:
> > In message: <200612251456.42770.amistry at am-productions.biz>
> >
> >             Anish Mistry <amistry at am-productions.biz> writes:
> > :  Many usb devices can be attached as different devices along with
> > : being functional with some libusb app that requires ugen.
> > : eg.  HP PSC Printers will attach as ulpt, if ulpt isn't loaded umass
> > : can attach to access the card slot, if neither of these are loaded
> > : ugen will attach which is required to run the hplip vendor software
> > : so that the printer, scanner, and fax machine can be accessed.
> >
> > You should review how the device presents itself to the system.  If
> > both umass and ulpt attach to it, it should be possible to make them
> > both attach at the same time.
> >
> > As for ugen, one could easily hack uhub to allow this kind of access.
> > ugen really shouldn't be attaching to any device at all, but instead
> > the usb bus (aka uhub) should allow ugen-like acess to each of the
> > devices.
> 
> Right.
> 
> Here are some pointers:
> 
> The core of your problem is "usbd_set_config()". Whenever you set a new config 
> value, you need to "device_delete_child()" all attached devices, and re-probe 
> the "struct usbd_device *" in question. Maybe you can extend the already 
> existing "usbd_remove_detached_devices()"?
> 
> Try making a system where the USB device config value is always set from 
> "usbd_probe_and_attach()", hence this function is always called from only one 
> thread at a time!
> 
> To force the system to re-call "usbd_probe_and_attach()", simply set 
> "up->last_refcount = 0", then call "usb_needs_explore()". "up" is of type 
> "struct usbd_port *".
> 
> Maybe you should add a new field:
> udev->current_config_value.
> 
> When "udev->probed == USBD_PROBED_SPECIFIC_AND_FOUND" disallow "/dev/ugenX" 
> from setting the config value.
> 
> Incorporate parts of ugen into "struct usbd_device":
> 
> 1) Split ugen into two parts, /dev/ugenX and /dev/ugenX.X .
> 2) /dev/ugenX is created by "usbd_new_device()".
> 3) /dev/ugenX is removed by "usbd_free_device()".
> 4) /dev/ugenX.X is a regular device that attaches when "uaa.iface != NULL" and 
> "uaa.usegeneric == 1". Maybe you have to remove 
> "USBD_PROBED_GENERIC_AND_FOUND".
> 
> There should be no problems in the USB stack regarding duplicate device 
> attachment. If two devices start a transfer on the same interrupt endpoint, 
> they will be served alternately, for example.

And don't forget to handle USB_SET_CONFIG properly...

-- 
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