linux-kernel - Re: Simple UART driver help and TTY questions

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Date:	Wed, 6 Aug 2008 14:46:35 -0700
From:	Ira Snyder <iws@...o.caltech.edu>
To:	Jiri Slaby <jirislaby@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Simple UART driver help and TTY questions

On Wed, Aug 06, 2008 at 11:11:00PM +0200, Jiri Slaby wrote:
> conOn 08/05/2008 06:33 PM, Ira Snyder wrote:
>> static void tiny_config_port(struct uart_port *port, int flags)
>> {
>> 	FUNC_ENTER();
>
>         if (flags & UART_CONFIG_TYPE)
>                 port->type = PORT_16550A;
>
>> }
>
> According to the straces, you get -EIO from ioctl and read which most 
> likely means TTY_IO_ERROR bit set due to tiny_port->type = PORT_UNKNOWN 
> (i.e. 0). Try the above.

Not quite, but it got me on the right track. I needed to set port->type
before calling uart_add_one_port().

Now it gets into my code. Previously, it had never even called any of my
code. None of it. Unfortunately, I ran it and it segfaulted. Turns out
that Greg's tinyserial driver didn't implement ops->set_termios() and
that was the cause. Implementing that got everything working.

Now I get in my dmesg:
[   73.813893] ttytiny: Tiny serial driver
[   83.714486] Enter: tiny_startup
[   83.717676] Enter: tiny_set_termios
[   83.721193] Enter: tiny_set_mctrl
[   85.463793] Enter: tiny_stop_rx
[   85.466987] Enter: tiny_set_mctrl
[   85.470328] Enter: tiny_shutdown

And that looks very reasonable. (It was produced by cat /dev/ttytiny0,
for your information).

Thanks a lot for your help! That problem had me completely stumped for a
couple of days now :)

Ira
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