Index: sys/geom/geom_dev.c
===================================================================
RCS file: /srv/ncvs/src/sys/geom/geom_dev.c,v
retrieving revision 1.96
diff -u -r1.96 geom_dev.c
--- sys/geom/geom_dev.c	16 Dec 2007 19:38:26 -0000	1.96
+++ sys/geom/geom_dev.c	15 Apr 2008 12:52:23 -0000
@@ -244,6 +244,7 @@
 {
 	struct g_geom *gp;
 	struct g_consumer *cp;
+	struct g_provider *pp;
 	struct g_kerneldump kd;
 	off_t offset, length, chunk;
 	int i, error;
@@ -251,6 +252,7 @@
 
 	gp = dev->si_drv1;
 	cp = dev->si_drv2;
+	pp = cp->provider;
 
 	error = 0;
 	KASSERT(cp->acr || cp->acw,
@@ -329,6 +331,12 @@
 	case DIOCGIDENT:
 		error = g_io_getattr("GEOM::ident", cp, &i, data);
 		break;
+	case DIOCGPROVIDERNAME:
+		if (pp == NULL)
+			return (ENOENT);
+
+		strlcpy(data, pp->name, MAXPATHLEN);
+		break;
 
 	default:
 		if (cp->provider->geom->ioctl != NULL) {
Index: sys/sys/disk.h
===================================================================
RCS file: /srv/ncvs/src/sys/sys/disk.h,v
retrieving revision 1.42
diff -u -r1.42 disk.h
--- sys/sys/disk.h	5 May 2007 17:02:19 -0000	1.42
+++ sys/sys/disk.h	15 Apr 2008 12:52:23 -0000
@@ -98,4 +98,9 @@
 	 * - ident is optional and applications can't relay on its presence.
 	 */
 
+#define DIOCGPROVIDERNAME _IOR('d', 138, char[MAXPATHLEN])
+	/*-
+	 * Store the provider name, given a device path, in a buffer.
+	 */
+
 #endif /* _SYS_DISK_H_ */
Index: lib/libgeom/geom_util.c
===================================================================
RCS file: /srv/ncvs/src/lib/libgeom/geom_util.c,v
retrieving revision 1.1
diff -u -r1.1 geom_util.c
--- lib/libgeom/geom_util.c	6 May 2007 01:17:46 -0000	1.1
+++ lib/libgeom/geom_util.c	15 Apr 2008 12:52:23 -0000
@@ -234,3 +234,70 @@
 	}
 	return (fd);
 }
+
+/*
+ * Return the provider name of a device given a partial or full path to its
+ * node.
+ */
+char *
+g_provider_from_path(const char *devpath)
+{
+	struct stat st;
+	char path[MAXPATHLEN];
+	char buffer[MAXPATHLEN];
+	int fd;
+
+	/* Use the device node if we're able to open it. */
+	do {
+		fd = open(devpath, O_RDONLY);
+		if (fd < 0)
+			break;
+
+		/* Make sure we're doing the ioctl on a device. */
+		if (fstat(fd, &st) < 0) {
+			close(fd);
+			break;
+		}
+		if (!(S_ISCHR(st.st_mode) || S_ISBLK(st.st_mode))) {
+			close(fd);
+			errno = EFTYPE;
+			break;
+		}
+		if (ioctl(fd, DIOCGPROVIDERNAME, buffer) < 0) {
+			close(fd);
+			if (errno == ENOTTY)
+				break;
+			errno = EFTYPE;
+			return (NULL);
+		}
+		close(fd);
+		return (strdup(buffer));
+	} while (0);
+
+	/* If we're not given an absolute path, assume /dev/ prefix. */
+	if (*devpath != '/') {
+		snprintf(path, MAXPATHLEN, "%s%s", _PATH_DEV, devpath);
+		fd = open(path, O_RDONLY);
+		if (fd < 0)
+			return (NULL);
+
+		/* Make sure we're doing the ioctl on a device. */
+		if (fstat(fd, &st) < 0) {
+			close(fd);
+			return (NULL);
+		}
+		if (!(S_ISCHR(st.st_mode) || S_ISBLK(st.st_mode))) {
+			close(fd);
+			errno = EFTYPE;
+			return (NULL);
+		}
+		if (ioctl(fd, DIOCGPROVIDERNAME, buffer) < 0) {
+			close(fd);
+			errno = EFTYPE;
+			return (NULL);
+		}
+		close(fd);
+		return (strdup(buffer));
+	}
+	return (NULL);
+}
Index: lib/libgeom/libgeom.h
===================================================================
RCS file: /srv/ncvs/src/lib/libgeom/libgeom.h,v
retrieving revision 1.12
diff -u -r1.12 libgeom.h
--- lib/libgeom/libgeom.h	6 May 2007 10:00:27 -0000	1.12
+++ lib/libgeom/libgeom.h	15 Apr 2008 12:52:23 -0000
@@ -154,6 +154,7 @@
 int g_get_ident(int, char *, size_t);
 int g_get_name(const char *, char *, size_t);
 int g_open_by_ident(const char *, int, char *, size_t);
+char *g_provider_from_path(const char *);
 
 __END_DECLS