linux-kernel - Re: [PATCH] USB: of: filter disabled device node

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Message-ID: <2025112237-brush-unseemly-7a95@gregkh>
Date: Sat, 22 Nov 2025 13:34:21 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: jerry xzq <jerry.xzq@...il.com>
Cc: linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] USB: of: filter disabled device node

On Sat, Nov 22, 2025 at 07:31:47PM +0800, jerry xzq wrote:
> On Sat, Nov 22, 2025 at 7:26 PM Zhengqiao Xia <jerry.xzq@...il.com> wrote:
> 
> > We should not point the of_node of a USB device to a disabled devicetree
> > node. Otherwise, the interface under this USB device will not be able
> > to register.
> >
> > Signed-off-by: Zhengqiao Xia <jerry.xzq@...il.com>
> > ---
> >  drivers/usb/core/of.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/usb/core/of.c b/drivers/usb/core/of.c
> > index 763e4122ed5b3..6bb577e711811 100644
> > --- a/drivers/usb/core/of.c
> > +++ b/drivers/usb/core/of.c
> > @@ -31,6 +31,9 @@ struct device_node *usb_of_get_device_node(struct
> > usb_device *hub, int port1)
> >                 if (of_property_read_u32(node, "reg", &reg))
> >                         continue;
> >
> > +               if (!of_device_is_available(node))
> > +                       continue;
> > +
> >                 if (reg == port1)
> >                         return node;
> >         }
> > --
> > 2.34.1
> >
> >  Supplementing questions from the previous email:
> 
> > What changed to require this?  What commit id does this fix?
> > And what devices have a disabled devicetree node?
> 
> fixes: 01fdf179f4b064d4c9d30(usb: core: skip interfaces disabled in
> devicetree )
> 
> Connect a USB device directly to the USB port, for me, LTE RW101.

Why?  Why not just us the normal USB device topology?  Why is this in DT
at all?

> However, a disabled node is attached to the DTS node of this port.

Why?

> &xhci3 {
>         status = "okay";
> 
>         /* 2.x hub on port 1 */
>         usb_hub_2_x: hub@1 {
>                 compatible = "usbbda,5411";
>                 reg = <1>;
>                 vdd-supply = <&pp3300_s3>;
>                 peer-hub = <&usb_hub_3_x>;
>                 status = "disabled";
> 
>                 ports {
>                         #address-cells = <1>;
>                         #size-cells = <0>;
>                         port@1 {
>                                 reg = <1>;
>                                 usb_hub_dsp1_hs: endpoint { };
>                         };
>                         port@2 {
>                                 reg = <2>;
>                                 usb_hub_dsp2_hs: endpoint { };
>                         };
>                         port@3 {
>                                 reg = <3>;
>                                 usb_hub_dsp3_hs: endpoint { };
>                         };
>                         port@4 {
>                                 reg = <4>;
> 
>                                 /* On-board WWAN card */
>                                 usb_hub_dsp4_hs: endpoint { };

That's the thing I don't want to see, why is that WWAN card described
here?  Why can't the normal USB device discovery find it and use it
properly?

>                         };
>                 };
>         };
> 
> Based on the current code, the of_node of this directly connected LTE
> device is hub.

But why is that needed?

> If there is only one LTE interface, then the of_node of this interface
> is also the hub.

Again, why?

> With the following code, the interface will be unable to create a device.
> 
> if (intf->dev.of_node &&
> !of_device_is_available(intf->dev.of_node)) {
> dev_info(&dev->dev, "skipping disabled interface %d\n",
> intf->cur_altsetting->desc.bInterfaceNumber);
> continue;
> }
> Then this LTE will be unable to create a device.
> this is not the result I wanted.

Then try removing it from dt entirely, it should not be necessary to
describe USB devices in dt.

thanks,

greg k-h