A termios path

[hjl@lucon.org (H.J. Lu)]

Hi,

This patch for glibc 2.1 works around a Linux kernel bug, which I don't
see any easy fix. Also

	cfsetispeed (termios_p, (speed_t) 0)

has a special meaning. It should set the input baud rate to the output
baud rate when tcsetattr is called with termios_p. I included a kludge
here.

Thanks.

H.J. Lu (hjl@gnu.org)
----
Sat Dec  5 23:13:24 1998  H.J. Lu  <hjl@gnu.org>

	* sysdeps/unix/sysv/linux/bits/termios.h (IBAUD0): NEW.

	* sysdeps/unix/sysv/linux/speed.c (cfgetispeed): New.
	(cfsetispeed): New.

	* sysdeps/unix/sysv/linux/tcsetattr.c (tcsetattr): Clear
	the IBAUD0 bit in c_iflag when making the system call.
	Work around a Linux kernel bug which silently changes the
	PARENB/CREAD/CSIZE bits in c_cflag on pty.

Index: sysdeps/unix/sysv/linux/bits/termios.h
===================================================================
RCS file: /home/work/cvs/gnu/glibc/sysdeps/unix/sysv/linux/bits/termios.h,v
retrieving revision 1.1.1.5
diff -u -p -r1.1.1.5 termios.h
--- sysdeps/unix/sysv/linux/bits/termios.h	1998/07/15 00:23:53	1.1.1.5
+++ sysdeps/unix/sysv/linux/bits/termios.h	1998/12/06 06:58:26
@@ -73,6 +73,9 @@ struct termios
 #define IXOFF	0010000
 #define IMAXBEL	0020000
 
+/* When this bit is set, the input baud rate is the numerical 0. */
+#define IBAUD0	020000000000
+
 /* c_oflag bits */
 #define OPOST	0000001
 #define OLCUC	0000002
Index: sysdeps/unix/sysv/linux/speed.c
===================================================================
RCS file: /home/work/cvs/gnu/glibc/sysdeps/unix/sysv/linux/speed.c,v
retrieving revision 1.1.1.2
diff -u -p -r1.1.1.2 speed.c
--- sysdeps/unix/sysv/linux/speed.c	1997/06/24 19:18:40	1.1.1.2
+++ sysdeps/unix/sysv/linux/speed.c	1998/12/06 18:54:20
@@ -31,8 +31,16 @@ cfgetospeed (termios_p)
 }
 
 /* Return the input baud rate stored in *TERMIOS_P.
-   For Linux there is no difference between input and output speed.  */
-strong_alias (cfgetospeed, cfgetispeed);
+   Although for Linux there is no difference between input and output
+   speed, the numerical 0 is a special case for the input baud rate. It
+   should set the input baud rate to the output baud rate. */
+speed_t
+cfgetispeed (termios_p)
+     const struct termios *termios_p;
+{
+  return (termios_p->c_iflag & IBAUD0)
+	 ? 0 : termios_p->c_cflag & (CBAUD | CBAUDEX);
+}
 
 /* Set the output baud rate stored in *TERMIOS_P to SPEED.  */
 int
@@ -54,5 +62,31 @@ cfsetospeed  (termios_p, speed)
 }
 
 /* Set the input baud rate stored in *TERMIOS_P to SPEED.
-   For Linux there is no difference between input and output speed.  */
-strong_alias (cfsetospeed, cfsetispeed);
+   Although for Linux there is no difference between input and output
+   speed, the numerical 0 is a special case for the input baud rate. It
+   should set the input baud rate to the output baud rate. */
+int
+cfsetispeed (termios_p, speed)
+     struct termios *termios_p;
+     speed_t speed;
+{
+  if ((speed & ~CBAUD) != 0
+      && (speed < B57600 || speed > B460800))
+    {
+      __set_errno (EINVAL);
+      return -1;
+    }
+
+  if (speed == 0)
+    {
+      termios_p->c_iflag |= IBAUD0;
+    }
+  else
+    {
+      termios_p->c_iflag &= ~IBAUD0;
+      termios_p->c_cflag &= ~(CBAUD | CBAUDEX);
+      termios_p->c_cflag |= speed;
+    }
+
+  return 0;
+}
Index: sysdeps/unix/sysv/linux/tcsetattr.c
===================================================================
RCS file: /home/work/cvs/gnu/glibc/sysdeps/unix/sysv/linux/tcsetattr.c,v
retrieving revision 1.1.1.3
diff -u -p -r1.1.1.3 tcsetattr.c
--- sysdeps/unix/sysv/linux/tcsetattr.c	1998/05/09 20:57:57	1.1.1.3
+++ sysdeps/unix/sysv/linux/tcsetattr.c	1998/12/06 19:06:30
@@ -37,6 +37,7 @@ tcsetattr (fd, optional_actions, termios
 {
   struct __kernel_termios k_termios;
   unsigned long int cmd;
+  int retval;
 
   switch (optional_actions)
     {
@@ -54,7 +55,7 @@ tcsetattr (fd, optional_actions, termios
       return -1;
     }
 
-  k_termios.c_iflag = termios_p->c_iflag;
+  k_termios.c_iflag = termios_p->c_iflag & ~IBAUD0;
   k_termios.c_oflag = termios_p->c_oflag;
   k_termios.c_cflag = termios_p->c_cflag;
   k_termios.c_lflag = termios_p->c_lflag;
@@ -68,5 +69,32 @@ tcsetattr (fd, optional_actions, termios
   memcpy (&k_termios.c_cc[0], &termios_p->c_cc[0],
 	  __KERNEL_NCCS * sizeof (cc_t));
 
-  return __ioctl (fd, cmd, &k_termios);
+  /* The Linux kernel has a bug which silently ignore the invalid
+     c_cflag on pty. We have to check it here. */
+  retval = __ioctl (fd, cmd, &k_termios);
+  if (retval == 0)
+    {
+      int save = errno;
+      retval = __ioctl (fd, TCGETS, &k_termios);
+      if (retval)
+	{
+	  /* We cannot verify if the setting is ok. We don't return
+	     an error (?). */
+	  __set_errno (save);
+	  retval = 0;
+	} 
+      else if ((termios_p->c_cflag & (PARENB | CREAD))
+			!= (k_termios.c_cflag & (PARENB | CREAD))
+	       || ((termios_p->c_cflag & CSIZE)
+		   && (termios_p->c_cflag & CSIZE)
+			!= (k_termios.c_cflag & CSIZE)))
+	{
+	  /* It looks like the Linux kernel silently changed the
+	     PARENB/CREAD/CSIZE bits in c_cflag. Report it as an
+	     error. */
+	  __set_errno (EINVAL);
+	  retval = -1;
+	}
+    }
+   return retval;
 }