Rtems_termios_ioctl problem

[Eric Norum]

Can someone who's familiar with the flow-control details of termios  
have a look at the interaction with this?

Why do you need to send a break?   The 'correct' way to do this would  
involve changes to low level drivers.  A workaround, for those  
applications that really need to drive the serial line to such a  
state, is to temporarily set the serial line speed to a lower value,  
then transmit a NUL character, wait the the transmitter is again  
idle, and restore the line speed.  Of course this means that any  
incoming characters will be mangled during this time.....

<Controversial>
My feeling is that the termios code is already too complicated and  
that all the code to support XON/XOFF flow control should be optional  
or removed.
Does anyone really use this antiquated and unreliable  means of flow  
control any more?
I'd be happy with leaving flow control up to the hardware (RTS/CTS)  
and dropping all references to flow control from the generic termios  
code.
/<Controversial>

On May 2, 2007, at 10:53 AM, Arquer Stephane wrote:

> Hi,
>
> Thanks for your answers, I've modified the file with your advices
>
> case TCFLSH:
> 	{
> 	switch (args->buffer) {
> 		case TCIFLUSH:	/* flush input buffer */
> 			{												
> 			if ( tty->rawInBuf.Tail != tty->rawInBuf.Head ) /* buffer is not  
> empty*/
> 				rtems_interrupt_disable (level);
> 				tty->rawInBuf.Head = tty->rawInBuf.Tail;
> 				rtems_interrupt_enable (level);
> 			}
> 			break;			
> 		case TCOFLUSH:	/* flush output buffer*/
> 			{
> 			if ( tty->rawOutBuf.Tail != tty->rawOutBuf.Head )/* buffer is  
> not empty*/
> 				rtems_interrupt_disable (level);
> 				tty->rawOutBuf.Head = tty->rawOutBuf.Tail;
> 				rtems_interrupt_enable (level);			
> 			}
> 			break;
> 				
> 		case TCIOFLUSH:	/* flush input & output buffer*/
> 			{
> 			if ( tty->rawInBuf.Tail != tty->rawInBuf.Head )
> 				rtems_interrupt_disable (level);
> 				tty->rawInBuf.Head = tty->rawInBuf.Tail;
> 				rtems_interrupt_enable (level);
> 						
> 			if ( tty->rawOutBuf.Tail != tty->rawOutBuf.Head )
> 				rtems_interrupt_disable (level);
> 				tty->rawOutBuf.Head = tty->rawOutBuf.Tail;
> 				rtems_interrupt_enable (level);	
> 			}
> 			break;
> 		}				
> 	}
> 	break;
>
> 	
> 	
> I call ioctl function with tcflush()
>
> int tcflush (int fd, int queue)
> {
> 	switch (queue){
> 		case TCIFLUSH:			
> 		case TCOFLUSH:
> 		case TCIOFLUSH:
> 			return ioctl(fd,TCFLSH,queue);
> 			break;
> 		default: return -1
> 		} //switch
> }
>
> And I am not sure that I'm using the handler ( args->buffer )in the  
> case TCFLSH correctly
>
> Another problem is for the TCSBRK case.
> Can you explain to me how can I send the break signal ?
>
> case TCSBRK:
> 	{
> 		??
> 	}
> 	break;	
>
>
> Thanks for your help.
>
> Stephane
>
>
>
>> -----Message d'origine-----
>> De : Eric Norum [mailto:norume at aps.anl.gov]
>> Envoyé : mercredi 2 mai 2007 16:00
>> À : Arquer Stephane
>> Cc : rtems-users at rtems.org
>> Objet : Re: Rtems_termios_ioctl problem
>>
>>
>> 1) Why place the NUL into the buffer?
>> 2) The raw input buffer is a ring buffer, so I don't think that your
>> rawnc calculation is right.
>> 3) The semaphore is being used for process synchronization, not for
>> mutual exclusion, so obtaining and releasing it like this is
>> incorrect.
>>
>>
>> It seems to me that all that's necessary is to:
>>          rtems_interrupt_disable (level);
>> 	tty->rawInBuf.Head = tty->rawInBuf.Tail;
>> 	rtems_interrupt_enable (level);
>>
>>
>> This will flush the 'raw' input buffer.  Should something happen to
>> the 'cooked' buffer as well?
>
> I don't use it for the moment.
>
>>
>>
>> On May 2, 2007, at 7:28 AM, Arquer Stephane wrote.  The comment at
>> the top of rtems_termios_enqueue_raw_characters
>>
>>> Hi,
>>>
>>> As I wrote in my previous email, I'm still trying to modify the
>>> file termios.c to add TCFLSH request like following:
>>>
>>> case TCFLSH:
>>> 	{
>>> 	switch (args->buffer) {
>>> 		case TCIFLUSH:	/* flush input buffer */
>>> 			{
>>> 			unsigned int head;
>>> 			sc = rtems_semaphore_obtain
>> (tty->rawInBuf.Semaphore,
>>> 								
>> 	RTEMS_WAIT,
>>> 								
>> 	RTEMS_NO_TIMEOUT);
>>> 								
>>> 			int rawnc = tty->rawInBuf.Tail -
>> tty->rawInBuf.Head;
>>> 			if ( rawnc < 0 )
>>> 				/* buffer is not empty*/ 	
>> 				
>>> 				head = tty->rawInBuf.Head;
>>> 				tty->rawInBuf.Tail = head;
>>> 				tty->rawInBuf.theBuf[head] = '\0';
>>> 					
>>> 			sc = rtems_semaphore_release
>> (tty->rawInBuf.Semaphore);					
>>> 			}
>>> 			break;
>>>
>>> I don't know if it is the correct way to flush the buffer. If
>>> someone knows how to do it,I'm interested.
>>>
>>> Thanks for your help.
>>>
>>> Stéphane.
>>>
>>>
>>> _______________________________________________
>>> rtems-users mailing list
>>> rtems-users at rtems.com
>>> http://rtems.rtems.org/mailman/listinfo/rtems-users
>>
>> -- 
>> Eric Norum <norume at aps.anl.gov>
>> Advanced Photon Source
>> Argonne National Laboratory
>> (630) 252-4793
>>
>>
>>

-- 
Eric Norum <norume at aps.anl.gov>
Advanced Photon Source
Argonne National Laboratory
(630) 252-4793