usb: dwc3: Allow usb role swich control from userspace

There is a possibility of user needs for USB mode switching on boards
that lack external hardware support for dynamic host/device role
detection. This is particularly relevant in automotive applications
where userspace applications need to switch USB roles (host to device)
at runtime for CarPlay/Android Auto integration.

Add an `allow_userspace_control` flag to handle such cases. When
enabled, it exposes a sysfs attribute that allows userspace to switch
the USB role manually between host and device. This provides flexibility
for platforms that cannot rely on hardware-based mode detection.

The role switch can be done as below
echo host > /sys/class/usb_role/<ADDR>.usb-role-switch/role
echo device > /sys/class/usb_role/<ADDR>.usb-role-switch/role

Acked-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Signed-off-by: Pritam Manohar Sutar <pritam.sutar@samsung.com>
Link: https://patch.msgid.link/20251024085455.789555-1-pritam.sutar@samsung.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/dwc3/drd.c b/drivers/usb/dwc3/drd.c
index 4c91240eb4299a034d7f777cb33f538f551e9330..589bbeb2745419331770b91919934c9524391e41 100644 (file)
--- a/drivers/usb/dwc3/drd.c
+++ b/drivers/usb/dwc3/drd.c
@@ -515,6 +515,7 @@ static int dwc3_setup_role_switch(struct dwc3 *dwc)
        dwc3_role_switch.set = dwc3_usb_role_switch_set;
        dwc3_role_switch.get = dwc3_usb_role_switch_get;
        dwc3_role_switch.driver_data = dwc;
+       dwc3_role_switch.allow_userspace_control = true;
        dwc->role_sw = usb_role_switch_register(dwc->dev, &dwc3_role_switch);
        if (IS_ERR(dwc->role_sw))
                return PTR_ERR(dwc->role_sw);