Re: serial flow control appears broken

[Lee Howard <faxguy@howardsilvan.com>]

Maciej W. Rozycki wrote:

> On Thu, 26 Jul 2007, Lee Howard wrote:
>
>  
>
> > If the application were to use TIOCM_RTS how would it know when to apply it or
> > not?  Is there some approach that the application could take to manage flow
> > control on the serial port?  What about software flow control?  Does the
> >    
>
> Well, an application could negate RTS when it receives a character and 
> is running out of resources for further processing of incoming data.
>
> Smarter UARTs may be able to negate RTS themselves based on the amount of 
> data in their receive FIFO.  The threshold may be configurable.

Okay, so let's say we've got a loop around a blocking read on the modem 
file descriptor...

 for (;;) {
     read some data from modem
     process data from modem
     if (end-of-data detected) break;
 }

Are you suggesting that the application should be using deasserting RTS 
after the read and asserting it before?

I had previously thought that the control of RTS was something that the 
serial/tty driver was supposed to do independently based on the buffer 
fill.  Was I wrong?

Thanks,

Lee.
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