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>
---
Changes in v2:
- updated commit message by mentioning usecase for this change.
- added 'Acked-by' tag
Link for v1: https://lore.kernel.org/linux-usb/20251020113723.553843-1-pritam.sutar@samsung.com/
drivers/usb/dwc3/drd.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/drivers/usb/dwc3/drd.c b/drivers/usb/dwc3/drd.c
index 4c91240eb429..589bbeb27454 100644
--- 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);
--
2.34.1