On Sat, Aug 07, 2010 at 11:25:21AM -0400, Dave Mielke wrote:
> One of our (brltty) users is reporting a problem which has begun to occur with
> his braille display. It turns out that the problem is actually with how Linux
> is interacting with the USB to serial adapter which he's using. dmesg reports
> that Linux is using its ftdi_sio driver.
>
> The problem is that the ftdi_sio driver's data toggle and the ftdi_sio
> adapter's data toggle are now at risk of starting out (opening of ttyUSB0) out
> of sync. I'm sure this is the problem because it's seemingly random, and, when
> it occurs, it corrects after a few data transfer attempts. As you'll see below,
> this is a new problem which the ftdi_sio driver didn't used to have. He's
> using a Debian system, so my references to kernel releases are what that
> distribution calls them.
>
> His ftdi_sio adapter worked fine up until, and including, kernel 2.6.32-3-686.
> Then, when he upgraded to kernel 2.6.32-5-686-18, the problem started to occur.
> It still occurs on Debian Unstable's kernel 2.6.32-5-686-19, and it even still
> occurs on Debian Experimental's kernel 2.6.35-rc6-686, so I suspect this is a
> problem which hasn't been addressed yet.
Ick, I've heard of this happening before on some devices, but I thought
we had fixed all of these a long time ago.
I think it is due to a host controller hardware bug somewhere,
especially given the work-arounds I've seen for this issue in a number
of different Windows USB drivers that we had to also add to some Linux
drivers.
Can this user test a patch out if I create one? If so, try the
one below please.
thanks,
greg k-h
diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index e298dc4..53517cc 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -805,6 +805,7 @@ static __u32 ftdi_232bm_baud_base_to_divisor(int baud, int base);
static __u32 ftdi_232bm_baud_to_divisor(int baud);
static __u32 ftdi_2232h_baud_base_to_divisor(int baud, int base);
static __u32 ftdi_2232h_baud_to_divisor(int baud);
+static int ftdi_attach(struct usb_serial *);
static struct usb_serial_driver ftdi_sio_device = {
.driver = {
@@ -832,6 +833,7 @@ static struct usb_serial_driver ftdi_sio_device = {
.ioctl = ftdi_ioctl,
.set_termios = ftdi_set_termios,
.break_ctl = ftdi_break_ctl,
+ .attach = ftdi_attach,
};
@@ -1891,6 +1893,12 @@ static void ftdi_break_ctl(struct tty_struct *tty, int break_state)
}
+static int ftdi_attach(struct usb_serial *serial)
+{
+ usb_reset_device(serial->dev);
+ return 0;
+}
+
/* old_termios contains the original termios settings and tty->termios contains
* the new setting to be used
* WARNING: set_termios calls this with old_termios in kernel space
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
