Re: [Fwd: I/O errors - confusion]

[Nick Garnett <nickg at ecoscentric dot com>]

Gary Thomas <gary at mlbassoc dot com> writes:

> On Tue, 2003-03-18 at 11:44, Nick Garnett wrote:
> > Gary Thomas <gary at mlbassoc dot com> writes:
> > 
> > > 
> > > I agree - either there is data or not and the return code should
> > > be very clear: EAGAIN means there is none, anything else means
> > > there was.  I think that the code in serial.c you quote should
> > > return no error when there is data.
> > 
> > That is exactly my interpretation of what should happen. The only real
> > question is whether we should make that change, or just fix it in the
> > fileio code. I would vote for the former, since it results in code
> > being removed, but we have to be sure we are not breaking anything
> > else by doing it.
> 
> I think that this patch fixes it [correctly]:
> 
> Index: io/serial/current/src/common/serial.c
> ===================================================================
> RCS file: /misc/cvsfiles/ecos/packages/io/serial/current/src/common/serial.c,v
> retrieving revision 1.17
> diff -u -5 -p -r1.17 serial.c
> --- io/serial/current/src/common/serial.c	23 May 2002 23:06:27 -0000	1.17
> +++ io/serial/current/src/common/serial.c	18 Mar 2003 23:37:03 -0000
> @@ -341,11 +341,11 @@ serial_write(cyg_io_handle_t handle, con
>  #ifdef CYGOPT_IO_SERIAL_SUPPORT_NONBLOCKING
>                      // Optionally return if configured for non-blocking mode.
>                      if (!cbuf->blocking) {
>                          *len -= size;   // number of characters actually sent
>                          cbuf->waiting = false;
> -                        res = -EAGAIN;
> +                        res = size == 0 ? -EAGAIN : ENOERROR;
>                          break;
>                      }
>  #endif // CYGOPT_IO_SERIAL_SUPPORT_NONBLOCKING
>                      cbuf->pending += size;  // Have this much more to send [eventually]
>                      if( !cyg_drv_cond_wait(&cbuf->wait) )
> @@ -438,11 +438,11 @@ serial_read(cyg_io_handle_t handle, void
>                  size++;
>              } else {
>  #ifdef CYGOPT_IO_SERIAL_SUPPORT_NONBLOCKING
>                  if (!cbuf->blocking) {
>                      *len = size;        // characters actually read
> -                    res = -EAGAIN;
> +                    res = size == 0 ? -EAGAIN : ENOERROR;
>                      break;
>                  }
>  #endif // CYGOPT_IO_SERIAL_SUPPORT_NONBLOCKING
>                  cbuf->waiting = true;
>  #ifdef XX_CYGDBG_DIAG_BUF
> 
> Comments?

Without actually trying it, that looks OK to me.

You should also be able to take the -EAGAIN tests out of dev_fo_read()
and dev_fo_write().

-- 
Nick Garnett                    eCos Kernel Architect
http://www.ecoscentric.com/     The eCos and RedBoot experts