Re: Out of tree GPL serial tty driver help?

[Peter Hurley <peter@hurleysoftware.com>]

On Fri, 2013-04-26 at 08:58 -0400, Mark Hounschell wrote:
> On 04/25/2013 05:41 PM, Peter Hurley wrote:
> > On Wed, 2013-04-24 at 13:44 -0400, Mark Hounschell wrote:
> >> I've been sort of maintaining a couple of Digi International serial port
> >> card (XP and AP) drivers for years now because, well, they just won't do
> >> it anymore. In any case, I'm moving from a 3.4.x kernel, that works just
> >> fine, to a 3.8.8 kernel, that does not. I have code that does something
> >> like this:
> >>
> >>       tty_set_operations(&SerialDriver, &SerialOps);
> >>       tty_register_driver(&SerialDriver);
> >>       maxminor = NumBoards * 64;
> >>       for (i = 0; i < maxminor; i++)
> >>           tty_register_device(&SerialDriver, i, NULL);
> >
> > You're correct in diagnosing the problem to cdevs == NULL.
> > You're missing:
> >
> > 	maxminor = min(num_boards * 64, 256);
> > 	serial_driver = alloc_tty_driver(maxminor);
> >
> > then,
> > 	/* Fill in pertinent tty_driver fields, esp. */
> > 	serial_driver->flags = TTY_DRIVER_DYNAMIC_DEV;
> >
> > 	tty_set_operations(serial_driver, &serial_ops);
> > 	tty_register_driver(serial_driver);
> > 	for (i = 0; i < maxminor; i++)
> > 		tty_register_device(serial_driver, i, NULL);
> >
> >
> 
> Thanks for responding Peter.
> 
> Earlier in the code they do this:
> 
> static struct tty_driver SerialDriver
> and things like
> SerialDriver.termios = kmalloc((maxminor - 256) * sizeof(TERMIOS *), 
                                  ^^^^^^^^^^^^^^
                                is this a transcription error?

> GFP_KERNEL);
> 
> So is the above no longer going to work and I _must_ now use 
> alloc_tty_driver?

Not required but functionally equivalent. alloc_tty_driver() is actually
a wrapper macro which calls __tty_alloc_driver(). You can verify your
driver behavior against that function, if you want.

> If alloc_tty_driver is now a requirement, how much is 
> it going to do for me? There are several things like the termios above 
> that are manually allocated. How much if any of this is alloc_tty_driver 
> going to do for me?

I can't answer this because I don't know what else your open-coded
method is doing.

> or might this work
> 
> static struct tty_driver SerialDriver
> .
> .
> .
>   	serial_driver.flags = TTY_DRIVER_DYNAMIC_DEV;
> 
>          SerialDriver.cdevs  = kcalloc(maxminor, 
> sizeof(SerialDriver.cdevs), GFP_KERNEL);
> 
>   	tty_set_operations(&serial_driver, &serial_ops);
>   	tty_register_driver(&serial_driver);
>   	for (i = 0; i < maxminor; i++)
>   		tty_register_device(&serial_driver, i, NULL);
> 
> ???
> 
> >
> > PS - Each board supports 64 individual serial ports??
> 
> No, this particular card comes in 4, 8, and 16 port flavors. I never did 
> understand why they create so many device entries. I just figured they 
> had a reason. For a single card, no matter how many ports, they create 
> 64 normal serial tty entries (tty_dgdm_G0 - tty_dgdm_G63), 64 serial 
> printer entries (lp_dgdm_G0 - lp_dgdm_G63), and then 64 serial modem 
> entries (cu_dgdm_G0 - cu_dgdm_G63). Don't know why.

So where does i/o go for tty_dgdm_G16?

Also, what host bus are these cards for?

Regards,
Peter Hurley