[src/trunk]: src/sys introduce DKCACHE_COMBINE() macro - it combines the flag...

[jdolecek <jdolecek%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/4983d9cc8d91
branches:  trunk
changeset: 352500:4983d9cc8d91
user:      jdolecek <jdolecek%NetBSD.org@localhost>
date:      Wed Apr 05 18:34:56 2017 +0000

description:
introduce DKCACHE_COMBINE() macro - it combines the flags in a way that
all common flags are retained, and flags regarding write cache are preserved
if either of the devices has it; callers can thus rely on write cache not
being possible to be used when both flags are missing

use the new macro for ccd(4)

diffstat:

 sys/dev/ccd.c  |   6 +++---
 sys/sys/dkio.h |  11 ++++++++++-
 2 files changed, 13 insertions(+), 4 deletions(-)

diffs (52 lines):

diff -r 1c7a69e5f964 -r 4983d9cc8d91 sys/dev/ccd.c
--- a/sys/dev/ccd.c     Wed Apr 05 10:44:35 2017 +0000
+++ b/sys/dev/ccd.c     Wed Apr 05 18:34:56 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: ccd.c,v 1.170 2017/03/30 16:50:32 jdolecek Exp $       */
+/*     $NetBSD: ccd.c,v 1.171 2017/04/05 18:34:56 jdolecek Exp $       */
 
 /*-
  * Copyright (c) 1996, 1997, 1998, 1999, 2007, 2009 The NetBSD Foundation, Inc.
@@ -88,7 +88,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: ccd.c,v 1.170 2017/03/30 16:50:32 jdolecek Exp $");
+__KERNEL_RCSID(0, "$NetBSD: ccd.c,v 1.171 2017/04/05 18:34:56 jdolecek Exp $");
 
 #if defined(_KERNEL_OPT)
 #include "opt_compat_netbsd.h"
@@ -1432,7 +1432,7 @@
                        if (i == 0)
                                dkcache = j;
                        else
-                               dkcache &= j;
+                               dkcache = DKCACHE_COMBINE(dkcache, j);
                }
 
                *((int *)data) = dkcache;
diff -r 1c7a69e5f964 -r 4983d9cc8d91 sys/sys/dkio.h
--- a/sys/sys/dkio.h    Wed Apr 05 10:44:35 2017 +0000
+++ b/sys/sys/dkio.h    Wed Apr 05 18:34:56 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: dkio.h,v 1.22 2015/12/08 20:36:15 christos Exp $       */
+/*     $NetBSD: dkio.h,v 1.23 2017/04/05 18:34:56 jdolecek Exp $       */
 
 /*
  * Copyright (c) 1987, 1988, 1993
@@ -86,6 +86,15 @@
 #define        DKCACHE_WCHANGE 0x000200 /* write enable is changeable */
 #define        DKCACHE_SAVE    0x010000 /* cache parameters are savable/save them */
 
+/*
+ * Combine disk cache flags of two drives to get common cache capabilities.
+ * All common flags are retained. Besides this, if one of the disks
+ * has a write cache enabled or changeable, propagate those flags into result,
+ * even if it's not shared, to indicate that write cache is present.
+ */
+#define DKCACHE_COMBINE(a, b) \
+       (((a) & (b)) | (((a) | (b)) & (DKCACHE_WRITE|DKCACHE_WCHANGE)))
+
                /* sync disk cache */
 #define        DIOCCACHESYNC   _IOW('d', 118, int)     /* sync cache (force?) */