On 26/10/2020 15:04, Samuel Thibault wrote:
Mark Cave-Ayland, le lun. 26 oct. 2020 13:40:05 +0000, a ecrit:
On 26/10/2020 13:00, Jason Andryuk wrote:
On Mon, Oct 26, 2020 at 7:21 AM Samuel Thibault <samuel.thiba...@gnu.org> wrote:
Aurelien, you introduced the "| 1" in
commit abb8a13918ecc1e8160aa78582de9d5224ea70df
Author: Aurelien Jarno <aurel...@aurel32.net>
Date: Wed Aug 13 04:23:17 2008 +0000
usb-serial: add support for modem lines
[...]
@@ -357,9 +393,9 @@ static int usb_serial_handle_control(USBDevice *dev, int
request, int value,
/* TODO: TX ON/OFF */
break;
case DeviceInVendor | FTDI_GET_MDM_ST:
- /* TODO: return modem status */
- data[0] = 0;
- ret = 1;
+ data[0] = usb_get_modem_lines(s) | 1;
+ data[1] = 0;
+ ret = 2;
break;
I'm not particularly familiar with the FTDI USB serial devices. I
found setting FTDI_THRE | FTDI_TEMT by comparing with real hardware.
A little searching found this:
https://elixir.bootlin.com/linux/latest/source/drivers/usb/serial/ftdi_sio.h#L541
That shows "B0 Reserved - must be 1", so maybe that is why "| 1" was added?
Right - that's for the modem status returned as part of the first 2 status
bytes for incoming data which is slightly different from modem status
returned directly from FTDI_SIO_GET_MODEM_STATUS:
https://elixir.bootlin.com/linux/latest/source/drivers/usb/serial/ftdi_sio.h#L423.
It is the latter which this patch changes and appears to match what I see on
my Chipi-X hardware here.
Aurelien, do you remember the reason for the addition of 1 here? It does
look like the confusion between the incoming data bytes and the modem
status bytes.
I spent a bit of time this morning doing some further tests on Linux using 2 machines
and a test program to check CTS and usbmon:
usbmon when adapter unplugged:
ffff95a4bf2dd300 2366831506 S Ci:4:004:0 s c0 05 0000 0000 0002 2 <
ffff95a4bf2dd300 2366831607 C Ci:4:004:0 0 2 = 0160
usbmon when adapter plugged in and remote connected to minicom:
ffff95a4452a79c0 2457273895 S Ci:4:004:0 s c0 05 0000 0000 0002 2 <
ffff95a4452a79c0 2457274057 C Ci:4:004:0 0 2 = 3160
It seems I made a mistake here since the response is interpreted as 2 bytes rather
than a single little-endian word: with CTS asserted on the remote the first byte is
0x31 == FTDI_CTS | FTDI_DSR | 1, whilst the 2nd byte is 0x60 == FTDI_THRE | FTDI_TEMT
which matches the existing QEMU code rather than the comments in ftdi_sio.h.
So sorry for the noise: I'll drop this patch from the series and post a v2
shortly.
ATB,
Mark.
