linux-serial-owner@xxxxxxxxxxxxxxx escribió el 24/01/2008 14:42:14:
Thank you very munch for your response Jean-Pierre. I think you understand
me.
> It has been known since long ago that this behaviour (which is required
to
> properly handle many RS485 devices) is not implemented by the serial
driver.
>
> So yes, you will have to implement it.
> There are several ways to do it, by creating a new line discipline as
> suggested by Russell King, or a new termios behaviour, or a new serial
> ioctl.
Yes, but, I am confused. A line discipline is oriented to translate data
not to handle flow control protocol , isn't It?
>
> In any case you will also need to add support for this in the 8250
driver
> itself. You can do this
> - by using special features of 82950 uarts (I did this once),
> - or by implementing RTS toggleing in software, which
> (1) is more difficult because there is no UART interrupt
> at the end of the byte serialization process,
> (2) is more flexible because you may want to handle a
> configurable delay between RTS rise/data/RTS fall,
> (3) is the only way with the 16C550 and earlier devices.
>
Yes, but it's only for 8250 uart. I think that all uarts have RTS pin. I
know it's not true, but
For example this code snipet from serial_core.c
static void __uart_start(struct tty_struct *tty)
{
struct uart_state *state = tty->driver_data;
struct uart_port *port = state->port;
if (!uart_circ_empty(&state->info->xmit) && state->info->xmit.buf
&&
!tty->stopped && !tty->hw_stopped)
port->ops->start_tx(port);
}
is it posible activate RTS just before start_tx() call using
uart_update_mctrl() function?
This shall be used by all uarts, isn't it?
Is it posible implement RTS handling on serial_core.c module to be common
to all uarts?
Thanks in avance
José Luis Zabalza
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