I can't send a break signal using my Belkin PDA Adapter. It uses
the mct_u232 USB serial driver. Looking deeper, I found I can't
change data bits, stop bits or parity either. All of these
functions depend on writing to the LCR (Line Control Register).
This is with 2.6.16-rc5.
I tried:
1) Connected the adapter to a Windows 2000 machine, where I can
use 7 data / even parity / 1 stop bit just fine. USBsnoop
says it is sending 0x9a in the Set LCR command. This matches
the docs for the mct_u232 except it also has bit 7 set:
[56931 ms] >>> URB 41 going down >>>
-- URB_FUNCTION_VENDOR_DEVICE:
TransferFlags = 00000000 (USBD_TRANSFER_DIRECTION_OUT,
~USBD_SHORT_TRANSFER_OK)
TransferBufferLength = 00000001
TransferBuffer = 81bc7a08
TransferBufferMDL = 00000000
00000000: 9a
UrbLink = 00000000
RequestTypeReservedBits = 00000000
Request = 00000007
Value = 00000000
Index = 00000000
2) Using a regular serial port, pressing control-A F in Minicom
sends the break signal to a Linux serial console but doesn't
work with the mct_u232 driver. I can't try this in Windows
because hyperterminal doesn't appear to know how to send a break.
3) I patched the mct_u232 driver to force bit 7 on when setting
communications mode but that made no difference:
--- 2.6.16-rc5-nb.orig/drivers/usb/serial/mct_u232.c
+++ 2.6.16-rc5-nb/drivers/usb/serial/mct_u232.c
@@ -635,6 +635,9 @@ static void mct_u232_set_termios (struct
last_lcr |= (cflag & CSTOPB) ?
MCT_U232_STOP_BITS_2 : MCT_U232_STOP_BITS_1;
+ if (le16_to_cpu(serial->dev->descriptor.idProduct) ==
MCT_U232_BELKIN_F5U109_PID)
+ last_lcr |= 0x80;
+
mct_u232_set_line_ctrl(serial, last_lcr);
/*
--
Chuck
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