From: Sergey Organov sorganov@gmail.com
[ Upstream commit e4bfded56cf39b8d02733c1e6ef546b97961e18a ]
Symptom: application opens /dev/ttyGS0 and starts sending (writing) to it while either USB cable is not connected, or nobody listens on the other side of the cable. If driver circular buffer overflows before connection is established, no data will be written to the USB layer until/unless /dev/ttyGS0 is closed and re-opened again by the application (the latter besides having no means of being notified about the event of establishing of the connection.)
Fix: on open and/or connect, kick Tx to flush circular buffer data to USB layer.
Signed-off-by: Sergey Organov sorganov@gmail.com Reviewed-by: Michał Mirosław mirq-linux@rere.qmqm.pl Signed-off-by: Felipe Balbi balbi@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/usb/gadget/function/u_serial.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c index 31e08bb3cb41e..58a699cfa4582 100644 --- a/drivers/usb/gadget/function/u_serial.c +++ b/drivers/usb/gadget/function/u_serial.c @@ -701,8 +701,10 @@ static int gs_start_io(struct gs_port *port) port->n_read = 0; started = gs_start_rx(port);
- /* unblock any pending writes into our circular buffer */ if (started) { + gs_start_tx(port); + /* Unblock any pending writes into our circular buffer, in case + * we didn't in gs_start_tx() */ tty_wakeup(port->port.tty); } else { gs_free_requests(ep, head, &port->read_allocated);