Fix for non-blocking serial write result code

[Andrew Lunn]

diff -u -r1.24 serial.c
--- packages/io/serial/current/src/common/serial.c	12 Sep 2003 15:32:50 -0000	1.24
+++ packages/io/serial/current/src/common/serial.c	12 Jan 2004 15:07:22 -0000
@@ -354,7 +354,7 @@
                     if (!cbuf->blocking) {
                         *len -= size;   // number of characters actually sent
                         cbuf->waiting = false;
-                        res = size == 0 ? -EAGAIN : ENOERR;
+                        res = (*len == 0) ? -EAGAIN : ENOERR;
                         break;
                     }
 #endif // CYGOPT_IO_SERIAL_SUPPORT_NONBLOCKING

I don't think this is correct either. The relevant standard is:
http://www.opengroup.org/onlinepubs/007904975/functions/write.html

It says:

When attempting to write to a file descriptor (other than a pipe or
FIFO) that supports non-blocking writes and cannot accept the data
immediately:

    * If the O_NONBLOCK flag is clear, write() shall block the calling
      thread until the data can be accepted.

    * If the O_NONBLOCK flag is set, write() shall not block the
      thread. If some data can be written without blocking the thread,
      write() shall write what it can and return the number of bytes
      written. Otherwise, it shall return -1 and set errno to
      [EAGAIN].

I think the code should be something like this. Comments please.

  Andrew

Index: packages/io/serial//current/ChangeLog
===================================================================
RCS file: /cvs/ecos/ecos/packages/io/serial/current/ChangeLog,v
retrieving revision 1.56
diff -u -r1.56 ChangeLog
--- packages/io/serial//current/ChangeLog       12 Sep 2003 15:32:49 -0000      1.56
+++ packages/io/serial//current/ChangeLog       17 Jan 2004 15:18:38 -0000
@@ -1,3 +1,9 @@
+2004-01-17  Andrew Lunn  <andrew.lunn@ascom.ch>
+
+       * src/common/serial.c (serial_write): Correctly handle
+       none-blocking write. If we can write some bytes, return without
+       error. If no bytes can be written return EAGAIN.
+
 2003-08-18  Jay Foster <jay@systech.com>
  
        * src/common/serial.c: Fixed bug for XON/XOFF flow control that
Index: packages/io/serial//current/src/common/serial.c
===================================================================
RCS file: /cvs/ecos/ecos/packages/io/serial/current/src/common/serial.c,v
retrieving revision 1.24
diff -u -r1.24 serial.c
--- packages/io/serial//current/src/common/serial.c     12 Sep 2003 15:32:50 -0000      1.24
+++ packages/io/serial//current/src/common/serial.c     17 Jan 2004 15:18:41 -0000
@@ -352,9 +352,14 @@
 #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 = size == 0 ? -EAGAIN : ENOERR;
+                        if (*len == size) {
+                          *len == -1;     // No bytes can written
+                          res = -EAGAIN;
+                        } else {
+                          *len -= size;   // number of characters actually sent
+                          res = ENOERR;
+                        }
                         break;
                     }
 #endif // CYGOPT_IO_SERIAL_SUPPORT_NONBLOCKING