| Message ID | 87pnfi8xc2.fsf@osv.gnss.ru |
|---|---|
| State | New |
| Headers | show |
| Series | usb: gadget: serial: fix Tx stall after buffer overflow | expand |
diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c index f986e5c..d333cda 100644 --- a/drivers/usb/gadget/function/u_serial.c +++ b/drivers/usb/gadget/function/u_serial.c @@ -563,6 +563,8 @@ static int gs_start_io(struct gs_port *port) /* unblock any pending writes into our circular buffer */ if (started) { + pr_debug("gs_start_tx: ttyGS%d\n", port->port_num); + gs_start_tx(port); tty_wakeup(port->port.tty); } else { gs_free_requests(ep, head, &port->read_allocated);
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. NOTE: current version of the driver leaks data from one connection to another through its internal circular buffer. It might be a good idea to clear the buffer on open/close/connect/disconnect, in which case the problem this patch solves would have been fixed in a different manner. However, not only that's a more dramatic change, but to do it right TTY-layer buffers are to be considered as well. Signed-off-by: Sergey Organov <sorganov@gmail.com> --- drivers/usb/gadget/function/u_serial.c | 2 ++ 1 file changed, 2 insertions(+)