From 8d25eb2c3a292113d6fd5b0f35ae3e3a40870a4f Mon Sep 17 00:00:00 2001
From: Poul-Henning Kamp <phk@FreeBSD.org>
Date: Sat, 9 Sep 2000 11:39:59 +0000
Subject: [PATCH] Add code to devname(3) so it can find the names of devices
 which were not present when dev_mkdb(8) was run.

First the dev_mkdb(8) database is searched, this caters for non-DEVFS
cases where people have renamed a device.

If that fails we ask the kernel using sysctl kern.devname if the device
driver has put a name in the dev_t.  This covers DEVFS cloned devices.

If that also fails we format a string which isn't entirely useless.
---
 lib/libc/gen/devname.3 |  1 +
 lib/libc/gen/devname.c | 39 +++++++++++++++++++++++++++------------
 sys/kern/kern_conf.c   | 27 +++++++++++++++++++++++++++
 3 files changed, 55 insertions(+), 12 deletions(-)

diff --git a/lib/libc/gen/devname.3 b/lib/libc/gen/devname.3
index b63d6c99996..2f39c80e9cd 100644
--- a/lib/libc/gen/devname.3
+++ b/lib/libc/gen/devname.3
@@ -41,6 +41,7 @@
 .Sh LIBRARY
 .Lb libc
 .Sh SYNOPSIS
+.Fd #include <sys/stat.h>
 .Fd #include <stdlib.h>
 .Ft char *
 .Fn devname "dev_t dev" "mode_t type"
diff --git a/lib/libc/gen/devname.c b/lib/libc/gen/devname.c
index 898c8e88d10..7d84037917a 100644
--- a/lib/libc/gen/devname.c
+++ b/lib/libc/gen/devname.c
@@ -29,6 +29,8 @@
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
+ *
+ * $FreeBSD$
  */
 
 #if defined(LIBC_SCCS) && !defined(lint)
@@ -36,6 +38,7 @@ static char sccsid[] = "@(#)devname.c	8.2 (Berkeley) 4/29/95";
 #endif /* LIBC_SCCS and not lint */
 
 #include <sys/types.h>
+#include <sys/sysctl.h>
 
 #include <db.h>
 #include <err.h>
@@ -85,21 +88,33 @@ devname(dev, type)
 	dev_t dev;
 	mode_t type;
 {
-	static char buf[20];
+	static char buf[30];	 /* XXX: pick up from <sys/conf.h> */
+	int i, j;
 	char *r;
 
+	/* First check the DB file. */
 	r = xdevname(dev, type);
-	if (!r) {
-		r = buf;
-		if (minor(dev) > 255) {
-			sprintf(buf, "#%c%d:0x%x", 
-			    (type & S_IFMT) == S_IFCHR ? 'C' : 'B',
-			    major(dev), minor(dev));
-		} else {
-			sprintf(buf, "#%c%d:%d", 
-			    (type & S_IFMT) == S_IFCHR ? 'C' : 'B',
-			    major(dev), minor(dev));
-		}
+	if (r != NULL)
+		return (r);
+
+	/* Then ask the kernel. */
+	if ((type & S_IFMT) == S_IFCHR) {
+		j = sizeof(buf);
+		i = sysctlbyname("kern.devname", buf, &j, &dev, sizeof (dev));
+		if (i == 0)
+		    return (buf);
+	}
+
+	/* Finally just format it */
+	r = buf;
+	if (minor(dev) > 255) {
+		sprintf(buf, "#%c%d:0x%x", 
+		    (type & S_IFMT) == S_IFCHR ? 'C' : 'B',
+		    major(dev), minor(dev));
+	} else {
+		sprintf(buf, "#%c%d:%d", 
+		    (type & S_IFMT) == S_IFCHR ? 'C' : 'B',
+		    major(dev), minor(dev));
 	}
 	return (r);
 }
diff --git a/sys/kern/kern_conf.c b/sys/kern/kern_conf.c
index fb15afdfcea..404f6f430e1 100644
--- a/sys/kern/kern_conf.c
+++ b/sys/kern/kern_conf.c
@@ -406,3 +406,30 @@ dev_stdclone(char *name, char **namep, char *stem, int *unit)
 		return (2);
 	return (1);
 }
+
+/*
+ * Helper sysctl for devname(3).  We're given a {u}dev_t and return
+ * the name, if any, registered by the device driver.
+ */
+static int
+sysctl_devname(SYSCTL_HANDLER_ARGS)
+{
+	int error;
+	udev_t ud;
+	dev_t dev;
+
+	error = SYSCTL_IN(req, &ud, sizeof (ud));
+	if (error)
+		return (error);
+	dev = makedev(umajor(ud), uminor(ud));
+	if (dev->si_name[0] == '\0')
+		error = ENOENT;
+	else
+		error = SYSCTL_OUT(req, dev->si_name, strlen(dev->si_name) + 1);
+	freedev(dev);
+	return (error);
+}
+
+SYSCTL_PROC(_kern, OID_AUTO, devname, CTLTYPE_OPAQUE|CTLFLAG_RW,
+	NULL, 0, sysctl_devname, "", "devname(3) handler");
+