[U-Boot-Users] PXA27x usbtty start up sequence

[Bryan O'Donoghue]

On Mon, 21 May 2007 00:23:42 +0200
Rodolfo Giometti <giometti at enneenne.com> wrote:
 
> The problem is that the defice __is__ into configured state (USB
> cable is connected and /dev/ttyUSB0 is running) but nobody has
> opened the serial line (no minicom/kermit running).
> 
> So, I suppose, the above modification is useless...

No, no, unless I'm *really* forgetting my USB enumeration behavior,
a device shouldn't go into the configured state unless and until
the host does a SET_CONFIGURATION, so the modification would be right
since without the USB cable connected the device should be in the
DEFAULT state, not the CONFIGURED state.

usb_20.pdf page - 240 Figure 9.1 see ?

> Mmm... I see... I supposed to get no control request once device is
> connected...
> 
> Currently I use a timeout of 2ms but I suppose I should decrease it,
> shouldn't I? :-o

Possibly... I don't think I'd take issue with the specific timeout
but, you *can* get a control request at *any* time... including 50% of
the way through a DATA IN transfer to the host... there's nothing in
the USB specification which precludes control requests on EP0 at
*any* time...

You'd probably "get away" with it if you limited your hardware to
functioning only with g_serial but, where would be the fun in doing
just g_serial ?
 
> Ok, what do you suggest to do? I'm a bit confused... :)

Possibly the simple solution is 

#1: Fix it so SET_CONFIGURATION is the only thing to move the device
into the configured state.

#2: Either you or I should write a patch then which looks like this.

/* Not tested */
static void __usbtty_puts (const char *str, int len)
{
	int maxlen = usbtty_output.totalsize;
	int space, n;

	/* break str into chunks < buffer size, if needed */
	while (len > 0 
	&& device_instance->device_state == STATE_CONFIGURED) { 
		usbtty_poll ();

		space = maxlen - usbtty_output.size;
		/* Empty buffer here, if needed, to ensure space... */
		if (space) {
			write_buffer (&usbtty_output);
			
			n = MIN (space, MIN (len, maxlen));
			buf_push (&usbtty_output, str, n);

			str += n;
			len -= n;
		}
	}
}

I think... that *should* work.

Happy Monday.


Bryan