Re: Linux tty layer hackery: Heads up and RFC

[Mark Underwood <basicmark@yahoo.com>]

Hi Alan,

Thanks for your help, I might give this ago once I've
fixed some flow control problems in my driver.

On a loosely related topic I have extended
serial_core.c to handle DMA UARTS (only the TX path is
effected). Once I'm happy with my changes I post a
patch.

Best Regards,

Mark

--- Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:

> On Maw, 2005-07-26 at 10:55 +0100, Mark Underwood
> wrote:
> > What my driver would like to do is to handle its
> own
> > input buffers. It would pass the buffer to the tty
> > layer when it is full and the tty layer would pass
> the
> 
> In theory you can do that already, although the
> locking is a bit screwed
> up for it. Actually all the tty locking is broken
> for rx I believe.
> Everyone should be holding the tty read lock when
> updating flip buffers
> but right now we don't
> 
> > buffer back once it has drained the data from it.
> > The problem is that I don't always receive a block
> > worth of characters so I also need to pass the tty
> > layer a buffer (which I'm still DMAing into) with
> a
> > count of how many chars there are in the buffer
> and a
> > offset of where to start from.
> 
> You can do this now providing you don't do it
> blindly from IRQ context.
> 
> >From a workqueue do
> 
> 	struct tty_ldisc *ld = tty_ldisc_ref(tty);
> 	int space;
> 
> 	if(ld == NULL)	/* Bin/defer */
> 		return;
> 	space = ld->receive_room(tty);
> 	if(count > space) count = space;
> 
> 	ld->receive_buf(tty, charbuf, flagbuf, count);
> 
> 
> There is a corner case if TTY_DONT_FLIP is set where
> you should queue
> but not all drivers do this and the DONT_FLIP hack
> 'has to die' 
> 
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