[PATCH] usb: gadget: udc: skip pullup() if already connected

[PATCH] usb: gadget: udc: skip pullup() if already connected

[Xu Yang]

The device controller may update vbus status via usb_udc_vbus_handler(),
which tries to connect the gadget even though gadget_bind_driver() has
already called usb_udc_connect_control_locked(). This causes pullup() to
be called twice. Avoid this by checking if gadget->connected is true.

Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
---
 drivers/usb/gadget/udc/core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
index e8861eaad907..be29daa7ad3c 100644
--- a/drivers/usb/gadget/udc/core.c
+++ b/drivers/usb/gadget/udc/core.c
@@ -712,6 +712,9 @@ static int usb_gadget_connect_locked(struct usb_gadget *gadget)
 		goto out;
 	}
 
+	if (gadget->connected)
+		goto out;
+
 	if (gadget->deactivated || !gadget->udc->allow_connect || !gadget->udc->started) {
 		/*
 		 * If the gadget isn't usable (because it is deactivated,
-- 
2.34.1

Re: [PATCH] usb: gadget: udc: skip pullup() if already connected

[Alan Stern]

On Tue, Apr 21, 2026 at 04:20:50PM +0800, Xu Yang wrote:
> The device controller may update vbus status via usb_udc_vbus_handler(),
> which tries to connect the gadget even though gadget_bind_driver() has
> already called usb_udc_connect_control_locked(). This causes pullup() to
> be called twice. Avoid this by checking if gadget->connected is true.

This patch is wrong.  To see why, read the comments just below the end 
of the patch and see also usb_gadget_activate().

(Also, is there really anything wrong with calling pullup() twice in a 
row?)

Alan Stern

> Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
> ---
>  drivers/usb/gadget/udc/core.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
> index e8861eaad907..be29daa7ad3c 100644
> --- a/drivers/usb/gadget/udc/core.c
> +++ b/drivers/usb/gadget/udc/core.c
> @@ -712,6 +712,9 @@ static int usb_gadget_connect_locked(struct usb_gadget *gadget)
>  		goto out;
>  	}
>  
> +	if (gadget->connected)
> +		goto out;
> +
>  	if (gadget->deactivated || !gadget->udc->allow_connect || !gadget->udc->started) {
>  		/*
>  		 * If the gadget isn't usable (because it is deactivated,
> -- 
> 2.34.1
> 
> 

Re: [PATCH] usb: gadget: udc: skip pullup() if already connected

[Bjørn Mork]

Alan Stern <stern@rowland.harvard.edu> writes:

> This patch is wrong.  To see why, read the comments just below the end 
> of the patch and see also usb_gadget_activate().


Made me look...

Must say. This strikes me as a nice way to filter out humans from the
rest of the submitters:

                gadget->connected = true;
                goto out;
        }
 
        ret = gadget->ops->pullup(gadget, 1);
        if (!ret)
                gadget->connected = 1;


The indecisiveness looks strange. There's a nice symmetry with
usb_gadget_disconnect_locked() though:

                gadget->connected = false;
                goto out;
        }
 
        ret = gadget->ops->pullup(gadget, 0);
        if (!ret)
                gadget->connected = 0;




What surprised me most was that the different variants were added by the
same commit
ccdf138fe3e2 ("usb: gadget: add usb_gadget_activate/deactivate functions").


Bjørn

Re: [PATCH] usb: gadget: udc: skip pullup() if already connected

[Alan Stern]

On Tue, Apr 21, 2026 at 05:27:32PM +0200, Bjørn Mork wrote:
> Alan Stern <stern@rowland.harvard.edu> writes:
> 
> > This patch is wrong.  To see why, read the comments just below the end 
> > of the patch and see also usb_gadget_activate().
> 
> 
> Made me look...
> 
> Must say. This strikes me as a nice way to filter out humans from the
> rest of the submitters:
> 
>                 gadget->connected = true;
>                 goto out;
>         }
>  
>         ret = gadget->ops->pullup(gadget, 1);
>         if (!ret)
>                 gadget->connected = 1;
> 
> 
> The indecisiveness looks strange. There's a nice symmetry with
> usb_gadget_disconnect_locked() though:
> 
>                 gadget->connected = false;
>                 goto out;
>         }
>  
>         ret = gadget->ops->pullup(gadget, 0);
>         if (!ret)
>                 gadget->connected = 0;

Granted, it does look a little strange.  ->connected is actually a 1-bit 
bitfield, though, so treating it as a boolean instead of an integer is 
not completely beyond the bounds of reason.

> What surprised me most was that the different variants were added by the
> same commit
> ccdf138fe3e2 ("usb: gadget: add usb_gadget_activate/deactivate functions").

But this isn't what my rejection was complaining about.  The patch's 
problem was functional, not aesthetic.

Alan Stern