[newlib-cygwin] ioccom: define ioctl cmd value that can never be valid

[Sebastian Huber <sh@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=19a627f3a45e6df12bd598b94afe562f8f5c6303

commit 19a627f3a45e6df12bd598b94afe562f8f5c6303
Author: Konstantin Belousov <kib@FreeBSD.org>
Date:   Thu Apr 22 22:40:08 2021 +0300

    ioccom: define ioctl cmd value that can never be valid
    
    Its use is for cases where some filler is needed for cmd, or we need an
    indication that there were no cmd supplied, and so on.
    
    Reviewed by:    jhb
    Sponsored by:   The FreeBSD Foundation
    MFC after:      1 week
    Differential revision:  https://reviews.freebsd.org/D29935

Diff:
---
 newlib/libc/sys/rtems/include/sys/ioccom.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/newlib/libc/sys/rtems/include/sys/ioccom.h b/newlib/libc/sys/rtems/include/sys/ioccom.h
index adaa30797..7b78db8e9 100644
--- a/newlib/libc/sys/rtems/include/sys/ioccom.h
+++ b/newlib/libc/sys/rtems/include/sys/ioccom.h
@@ -84,6 +84,9 @@ typedef unsigned long ioctl_command_t;
 #define	IOCPARM_IVAL(x)	((int)(intptr_t)(void *)*(caddr_t *)(void *)(x))
 #endif
 
+#define	_IOC_INVALID	(_IOC_VOID|_IOC_INOUT)	/* Never valid cmd value,
+						   use as filler */
+
 #endif
 
 __BEGIN_DECLS