Commit 647ee987 authored by Jason Andryuk's avatar Jason Andryuk Committed by Gerd Hoffmann
Browse files

usb-serial: Fix timeout closing the device 



Linux guests wait ~30 seconds when closing the emulated /dev/ttyUSB0.
During that time, the kernel driver is sending many control URBs
requesting GetModemStat (5).  Real hardware returns a status with
FTDI_THRE (Transmitter Holding Register) and FTDI_TEMT (Transmitter
Empty) set.  QEMU leaves them clear, and it seems Linux is waiting for
FTDI_TEMT to be set to indicate the tx queue is empty before closing.

Set the bits when responding to a GetModemStat query and avoid the
shutdown delay.

Signed-off-by: default avatarJason Andryuk <jandryuk@gmail.com>
Reviewed-by: default avatarSamuel Thibault <samuel.thibault@ens-lyon.org>
Message-id: 20200316174610.115820-5-jandryuk@gmail.com
Signed-off-by: default avatarGerd Hoffmann <kraxel@redhat.com>
parent 30ad5fdd

hw/usb/dev-serial.c

+1 −1
Original line number Diff line number Diff line
@@ -332,7 +332,7 @@ static void usb_serial_handle_control(USBDevice *dev, USBPacket *p, 
        break;

    case DeviceInVendor | FTDI_GET_MDM_ST:

        data[0] = usb_get_modem_lines(s) | 1;

        data[1] = 0;

        data[1] = FTDI_THRE | FTDI_TEMT;

        p->actual_length = 2;

        break;

    case DeviceOutVendor | FTDI_SET_EVENT_CHR: