[PATCH] usb: gadget: udc: Clear a pending connection when starting the UDC

[PATCH] usb: gadget: udc: Clear a pending connection when starting the UDC

[Alexey Charkov]

Since commit 62911bc82b03 ("usb: gadget: udc: skip pullup() if already
connected"), usb_gadget_connect_locked() returns early when
gadget->connected is set. A connection requested while the UDC is
stopped sets that flag too, without enabling the pullup. A later
gadget_bind_driver() or soft_connect "connect" then finds it set and
never enables the pullup, so the host doesn't see the gadget until it is
unbound and bound again.

This happens whenever a UDC driver reports VBUS through
usb_udc_vbus_handler() while no gadget driver is bound, e.g. when a
Type-C port controller switches the controller to the device role at
boot, seconds before userspace binds a configfs gadget.

The pullup is never enabled while the UDC is stopped, so clear
gadget->connected once it starts. The bind connects according to the
VBUS state that the core tracks anyway, and a function that deactivates
the gadget during bind still has the connection recorded for
usb_gadget_activate().

Fixes: 62911bc82b03 ("usb: gadget: udc: skip pullup() if already connected")
Cc: stable@vger.kernel.org
Signed-off-by: Alexey Charkov <alchark@flipper.net>
---
 drivers/usb/gadget/udc/core.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
index d5844384c368..577bc15f61a1 100644
--- a/drivers/usb/gadget/udc/core.c
+++ b/drivers/usb/gadget/udc/core.c
@@ -1236,8 +1236,16 @@ static inline int usb_gadget_udc_start_locked(struct usb_udc *udc)
 	}
 
 	ret = udc->gadget->ops->udc_start(udc->gadget, udc->driver);
-	if (!ret)
+	if (!ret) {
 		udc->started = true;
+		/*
+		 * The pullup is never enabled while the UDC is stopped, so any
+		 * connection recorded meanwhile was only a request. Forget it,
+		 * so that the next usb_gadget_connect_locked() enables the
+		 * pullup rather than returning early.
+		 */
+		udc->gadget->connected = false;
+	}
 
 	return ret;
 }

---
base-commit: aaa2f954c21b205a0bcd0961e5b2be4e82e58455
change-id: 20261112-udc-connect-61e0f11cf93b

Best regards,
--  
Alexey Charkov <alchark@flipper.net>

Re: [PATCH] usb: gadget: udc: Clear a pending connection when starting the UDC

[sashiko-bot]

> Since commit 62911bc82b03 ("usb: gadget: udc: skip pullup() if already
> connected"), usb_gadget_connect_locked() returns early when
> gadget->connected is set. A connection requested while the UDC is
> stopped sets that flag too, without enabling the pullup. A later
> gadget_bind_driver() or soft_connect "connect" then finds it set and
> never enables the pullup, so the host doesn't see the gadget until it is
> unbound and bound again.
> 
> This happens whenever a UDC driver reports VBUS through
> usb_udc_vbus_handler() while no gadget driver is bound, e.g. when a
> Type-C port controller switches the controller to the device role at
> boot, seconds before userspace binds a configfs gadget.
> 
> The pullup is never enabled while the UDC is stopped, so clear
> gadget->connected once it starts. The bind connects according to the
> VBUS state that the core tracks anyway, and a function that deactivates
> the gadget during bind still has the connection recorded for
> usb_gadget_activate().
> 
> Fixes: 62911bc82b03 ("usb: gadget: udc: skip pullup() if already connected")
> Cc: stable@vger.kernel.org
> Signed-off-by: Alexey Charkov <alchark@flipper.net>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261112-udc-connect-v1-1-03c73259642b@flipper.net?part=1