Rtems_termios_ioctl problem

[Arquer Stephane]

Thomas,

Thanks a lot for your explanations, for the moment the input flush seems to work fine.
I've add interrupts control inside the function InputFlowCheckResume.

Kind regards.
Stéphane.


> -----Message d'origine-----
> De : Thomas Doerfler [mailto:Thomas.Doerfler at embedded-brains.de] 
> Envoyé : jeudi 3 mai 2007 11:46
> À : Arquer Stephane
> Cc : rtems-users at rtems.org
> Objet : Re: RE : Rtems_termios_ioctl problem
> 
> 
> Stephane,
> 
> the input direction looks fine for me with one exception: the 
> function InputFlowCheckResume should be executed with 
> interrupts disabled, otherwise "rawOutBufState" could change 
> its state after it has been checked and before the (*write) 
> function is executed.
> 
> But I am quite unsure about the output direction: in 
> interrupt driven mode, termios will present the buffer 
> between head and tail (or part of
> it) to the driver's write function, and some time later, the 
> driver will  call rtems_termios_dequeue_characters(tty,len) 
> to indicate, that it has sent out the whole or part of this buffer.
> 
> What happens, when you meanwhile modify "head" (and possibly 
> add new output characters to the buffer afterwards)? Either 
> the driver will send out stale data, new data out of proper 
> order, or the head/tail management may totally come out of 
> sync in this situation.
> 
> I am not sure what will happen, but I think your output Flush 
> needs further rethinking.
> 
> wkr,
> Thomas.
> 
> 
> Arquer Stephane schrieb:
> > Hi,
> > 
> > If my understanding is correct, in the case of using the flow ctrl 
> > mode  XON/XOFF or RTS we need to send these controls to 
> indicate that 
> > the input buffer has enough space for further reception. So , I've 
> > added the corresponding code when flushing input buffer like 
> > following.
> > 
> > 
> > 
> > /*
> >  *	helper subroutine which checks if XON must be sent
> >  *  it takes also care of the HW flow control
> >  */
> > static rtems_status_code InputFlowCheckResume (struct 
> rtems_termios_tty *tty)
> > {	
> > /* if tx stopped and XON should be sent... */
> > 	if (((tty->flow_ctrl & (FL_MDXON | FL_ISNTXOF))
> >     	==                (FL_MDXON | FL_ISNTXOF))
> > 		&& ((tty->rawOutBufState == rob_idle)
> > 		|| (tty->flow_ctrl & FL_OSTOP))) {
> >     	/* XON should be sent now... */
> >     	(*tty->device.write)(tty->minor, 
> &(tty->termios.c_cc[VSTART]), 1);
> > 	}
> > 	else if (tty->flow_ctrl & FL_MDRTS) {		    
> >     	tty->flow_ctrl &= ~FL_IRTSOFF;		
> >     	/* activate RTS line */
> > 	    if (tty->device.startRemoteTx != NULL) {
> > 	      tty->device.startRemoteTx(tty->minor);
> > 	    }
> >  	} 	
> >  	return RTEMS_SUCCESSFUL; 	
> > } // InputFlowCheckResume()
> > 
> > 
> > rtems_status_code rtems_termios_ioctl (void *arg){
> > ...
> > 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);
> > 					sc = InputFlowCheckResume(tty);
> > 					}
> > 				}
> > 				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);
> > 					sc = InputFlowCheckResume(tty);	
> > 					}			
> 				
> > 				if ( tty->rawOutBuf.Tail != 
> tty->rawOutBuf.Head ) {
> > 					rtems_interrupt_disable (level);
> > 					tty->rawOutBuf.Head = 
> tty->rawOutBuf.Tail;
> > 					rtems_interrupt_enable (level);
> > 					}
> > 				}
> > 				break;
> > ...
> > 
> > 
> > Kind regards.
> > 
> > Stéphane.
> > 
> >> -----Message d'origine-----
> >> De : Thomas Doerfler [mailto:Thomas.Doerfler at imd-systems.de]
> >> Envoyé : mercredi 2 mai 2007 22:30
> >> À : Joel Sherrill
> >> Cc : Eric Norum; rtems-users at rtems.org; Arquer Stephane
> >> Objet : Re: RE : Rtems_termios_ioctl problem
> >>
> >>
> >> Joel,
> >>
> >> Joel Sherrill schrieb:
> >>> Thomas Doerfler wrote:
> >>>
> >>>   
> >> Should this code be moved to a helper subroutine that is
> >> invoked from both places?
> >>
> >> Yes Joel, this would be nice, especially since it only
> >> requires "tty" as an argument. The name of this function 
> >> could be "inputFlowCheckResume" or something like this...
> >>
> >> Stephane, can you try to implement this?
> >>
> >> wkr,
> >> Thomas.
> >>
> >> --
> >> --------------------------------------------
> >> IMD Ingenieurbuero fuer Microcomputertechnik
> >> Thomas Doerfler           Herbststrasse 8
> >> D-82178 Puchheim          Germany
> >> email:    Thomas.Doerfler at imd-systems.de
> >> PGP public key available at:
> >>      http://www.imd-systems.de/pgpkey_en.html
> >>
> > 
> > _______________________________________________
> > rtems-users mailing list
> > rtems-users at rtems.com 
> > http://rtems.rtems.org/mailman/listinfo/rtems-users
> 
> 
> -- 
> --------------------------------------------
> embedded brains GmbH
> Thomas Doerfler           Obere Lagerstr. 30
> D-82178 Puchheim          Germany
> Tel. : +49-89-18 90 80 79-2
> Fax  : +49-89-18 90 80 79-9
> email: Thomas.Doerfler at embedded-brains.de
> PGP public key available on request
> 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: termios.c
Type: application/octet-stream
Size: 42189 bytes
Desc: termios.c
URL: <http://lists.rtems.org/pipermail/users/attachments/20070504/31c21a0c/attachment-0002.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: tcflush.c
Type: application/octet-stream
Size: 808 bytes
Desc: tcflush.c
URL: <http://lists.rtems.org/pipermail/users/attachments/20070504/31c21a0c/attachment-0003.obj>