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[PULL 4/4] usb-serial: Fix timeout closing the device
From: |
Gerd Hoffmann |
Subject: |
[PULL 4/4] usb-serial: Fix timeout closing the device |
Date: |
Tue, 17 Mar 2020 10:50:49 +0100 |
From: Jason Andryuk <address@hidden>
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: Jason Andryuk <address@hidden>
Reviewed-by: Samuel Thibault <address@hidden>
Message-id: address@hidden
Signed-off-by: Gerd Hoffmann <address@hidden>
---
hw/usb/dev-serial.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/hw/usb/dev-serial.c b/hw/usb/dev-serial.c
index 77b964588b5f..d2c03681b7f0 100644
--- a/hw/usb/dev-serial.c
+++ b/hw/usb/dev-serial.c
@@ -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:
--
2.18.2