[PATCH] experimental (very simple) SYMLINK creation

> > here is a experimental symlink creation patch - for discussion,
> > in which direction we should go.
> > It is possible now to define SYMLINK= after the NAME= in udev.rules.
> > The link is relative to the node, but the path is not optimized now
> > if the node and the link are in the same nested directory.
> > Only one link is supported, cause i need to sleep now :)
> >
> > 06-simple-symlink-creation.diff
> >   simple symlink creation
> >   reorganized udev-remove to have access to the symlink field
> >   subdir creation/removal are functions now
> >   udev-test.pl tests for link creation/removal

Here is a new version with relative link target path optimization
an better tests in udev-test.pl:

LABEL, BUS="scsi", vendor="IBM-ESXS", NAME="1/2/a/b/node", SYMLINK="1/2/c/d/symlink"

  Dec  7 06:48:34 pim udev[13789]: create_node: symlink 'udev-root/1/2/c/d/symlink' to node '1/2/a/b/node' requested
  Dec  7 06:48:34 pim udev[13789]: create_path: created 'udev-root/1/2/c'
  Dec  7 06:48:34 pim udev[13789]: create_path: created 'udev-root/1/2/c/d'
  Dec  7 06:48:34 pim udev[13789]: create_node: symlink(../../a/b/node, udev-root/1/2/c/d/symlink)

namedev.c

@@ -121,6 +121,7 @@ int add_config_dev(struct config_device *new_dev)
 		copy_string(dev, new_dev, place);
 		copy_string(dev, new_dev, kernel_name);
 		copy_string(dev, new_dev, exec_program);
+		copy_string(dev, new_dev, symlink);
 		return 0;
 	}
 
@@ -366,6 +367,7 @@ static int do_callout(struct sysfs_class_device *class_dev, struct udevice *udev
 		if (strcmp_pattern(dev->id, udev->callout_value) != 0)
 			continue;
 		strfieldcpy(udev->name, dev->name);
+		strfieldcpy(udev->symlink, dev->symlink);
 		dbg("callout returned matching value '%s', '%s' becomes '%s'",
 		    dev->id, class_dev->name, udev->name);
 		return 0;
@@ -416,6 +418,7 @@ label_found:
 			continue;
 
 		strfieldcpy(udev->name, dev->name);
+		strfieldcpy(udev->symlink, dev->symlink);
 		dbg("found matching attribute '%s', '%s' becomes '%s' ",
 		    dev->sysfs_file, class_dev->name, udev->name);
 
@@ -461,6 +464,7 @@ static int do_number(struct sysfs_class_device *class_dev, struct udevice *udev,
 		if (!found)
 			continue;
 		strfieldcpy(udev->name, dev->name);
+		strfieldcpy(udev->symlink, dev->symlink);
 		dbg("found matching id '%s', '%s' becomes '%s'",
 		    dev->id, class_dev->name, udev->name);
 		return 0;
@@ -506,6 +510,7 @@ static int do_topology(struct sysfs_class_device *class_dev, struct udevice *ude
 			continue;
 
 		strfieldcpy(udev->name, dev->name);
+		strfieldcpy(udev->symlink, dev->symlink);
 		dbg("found matching place '%s', '%s' becomes '%s'",
 		    dev->place, class_dev->name, udev->name);
 		return 0;
@@ -528,6 +533,7 @@ static int do_replace(struct sysfs_class_device *class_dev, struct udevice *udev
 			continue;
 
 		strfieldcpy(udev->name, dev->name);
+		strfieldcpy(udev->symlink, dev->symlink);
 		dbg("found name, '%s' becomes '%s'", dev->kernel_name, udev->name);
 		
 		return 0;
@@ -618,8 +624,9 @@ int namedev_name_device(struct sysfs_class_device *class_dev, struct udevice *ud
 	goto done;
 
 found:
-	/* substitute placeholder in NAME  */
+	/* substitute placeholder */
 	apply_format(udev, udev->name);
+	apply_format(udev, udev->symlink);
 
 done:
 	perm = find_perm(udev->name);

namedev.h

@@ -63,6 +63,7 @@ struct config_device {
 	char kernel_name[NAME_SIZE];
 	char exec_program[FILE_SIZE];
 	char name[NAME_SIZE];
+	char symlink[NAME_SIZE];
 };
 
 struct perm_device {

namedev_parse.c

@@ -213,10 +213,16 @@ int namedev_init_rules(void)
 				break;
 			strfieldcpy(dev.name, temp3);
 
+			/* SYMLINK="name" */
+			temp2 = strsep(&temp, ",");
+			retval = get_value("SYMLINK", &temp, &temp3);
+			if (retval == 0)
+				strfieldcpy(dev.symlink, temp3);
+
 			dbg_parse("LABEL name='%s', bus='%s', "
-				  "sysfs_file='%s', sysfs_value='%s'",
+				  "sysfs_file='%s', sysfs_value='%s', symlink='%s'",
 				  dev.name, dev.bus, dev.sysfs_file,
-				  dev.sysfs_value);
+				  dev.sysfs_value, dev.symlink);
 		}
 
 		if (strcasecmp(temp2, TYPE_NUMBER) == 0) {
@@ -243,8 +249,14 @@ int namedev_init_rules(void)
 				break;
 			strfieldcpy(dev.name, temp3);
 
-			dbg_parse("NUMBER name='%s', bus='%s', id='%s'",
+			/* SYMLINK="name" */
-				  dev.name, dev.bus, dev.id);
+			temp2 = strsep(&temp, ",");
+			retval = get_value("SYMLINK", &temp, &temp3);
+			if (retval == 0)
+				strfieldcpy(dev.symlink, temp3);
+
+			dbg_parse("NUMBER name='%s', bus='%s', id='%s', symlink='%s'",
+				  dev.name, dev.bus, dev.id, dev.symlink);
 		}
 
 		if (strcasecmp(temp2, TYPE_TOPOLOGY) == 0) {
@@ -271,8 +283,15 @@ int namedev_init_rules(void)
 				break;
 			strfieldcpy(dev.name, temp3);
 
-			dbg_parse("TOPOLOGY name='%s', bus='%s', place='%s'",
+			/* SYMLINK="name" */
-				  dev.name, dev.bus, dev.place);
+			temp2 = strsep(&temp, ",");
+			retval = get_value("SYMLINK", &temp, &temp3);
+			if (retval == 0)
+				strfieldcpy(dev.symlink, temp3);
+
+			dbg_parse("TOPOLOGY name='%s', bus='%s', "
+				  "place='%s', symlink='%s'",
+				  dev.name, dev.bus, dev.place, dev.symlink);
 		}
 
 		if (strcasecmp(temp2, TYPE_REPLACE) == 0) {
@@ -291,9 +310,17 @@ int namedev_init_rules(void)
 			if (retval)
 				break;
 			strfieldcpy(dev.name, temp3);
-			dbg_parse("REPLACE name='%s', kernel_name='%s'",
+
-				  dev.name, dev.kernel_name);
+			/* SYMLINK="name" */
+			temp2 = strsep(&temp, ",");
+			retval = get_value("SYMLINK", &temp, &temp3);
+			if (retval == 0)
+				strfieldcpy(dev.symlink, temp3);
+
+			dbg_parse("REPLACE name='%s', kernel_name='%s', symlink='%s'",
+				  dev.name, dev.kernel_name, dev.symlink);
 		}
+
 		if (strcasecmp(temp2, TYPE_CALLOUT) == 0) {
 			/* number type */
 			dev.type = CALLOUT;
@@ -324,8 +351,17 @@ int namedev_init_rules(void)
 			if (retval)
 				break;
 			strfieldcpy(dev.name, temp3);
-			dbg_parse("CALLOUT name='%s', program='%s'",
+
-				  dev.name, dev.exec_program);
+			/* SYMLINK="name" */
+			temp2 = strsep(&temp, ",");
+			retval = get_value("SYMLINK", &temp, &temp3);
+			if (retval == 0)
+				strfieldcpy(dev.symlink, temp3);
+
+			dbg_parse("CALLOUT name='%s', bus='%s', program='%s', "
+				  "id='%s', symlink='%s'",
+				  dev.name, dev.bus, dev.exec_program,
+				  dev.id, dev.symlink);
 		}
 
 		retval = add_config_dev(&dev);
@@ -414,7 +450,7 @@ int namedev_init_permissions(void)
 			  dev.mode);
 		retval = add_perm_dev(&dev);
 		if (retval) {
-			dbg("add_config_dev returned with error %d", retval);
+			dbg("add_perm_dev returned with error %d", retval);
 			goto exit;
 		}
 	}

test/udev-test.pl

@@ -39,7 +39,7 @@ my @tests = (
 		expected => "boot_disk" ,
 		conf     => <<EOF
 LABEL, BUS="scsi", vendor="IBM-ESXS", NAME="boot_disk%n"
-REPLACE, KERNEL="ttyUSB0", NAME="visor""
+REPLACE, KERNEL="ttyUSB0", NAME="visor"
 EOF
 	},
 	{
@@ -179,6 +179,42 @@ EOF
 CALLOUT, BUS="usb", PROGRAM="/bin/echo -n usb-%b", ID="*", NAME="%c"
 CALLOUT, BUS="scsi", PROGRAM="/bin/echo -n scsi-%b", ID="*", NAME="%c"
 CALLOUT, BUS="foo", PROGRAM="/bin/echo -n foo-%b", ID="*", NAME="%c"
+EOF
+	},
+	{
+		desc     => "symlink creation (same directory)",
+		subsys   => "tty",
+		devpath  => "class/tty/ttyUSB0",
+		expected => "visor0" ,
+		conf     => <<EOF
+REPLACE, KERNEL="ttyUSB[0-9]*", NAME="ttyUSB%n", SYMLINK="visor%n"
+EOF
+	},
+	{
+		desc     => "symlink creation (relative link back)",
+		subsys   => "block",
+		devpath  => "block/sda/sda2",
+		expected => "1/2/a/b/symlink" ,
+		conf     => <<EOF
+LABEL, BUS="scsi", vendor="IBM-ESXS", NAME="1/2/node", SYMLINK="1/2/a/b/symlink"
+EOF
+	},
+	{
+		desc     => "symlink creation (relative link forward)",
+		subsys   => "block",
+		devpath  => "block/sda/sda2",
+		expected => "1/2/symlink" ,
+		conf     => <<EOF
+LABEL, BUS="scsi", vendor="IBM-ESXS", NAME="1/2/a/b/node", SYMLINK="1/2/symlink"
+EOF
+	},
+	{
+		desc     => "symlink creation (relative link back and forward)",
+		subsys   => "block",
+		devpath  => "block/sda/sda2",
+		expected => "1/2/c/d/symlink" ,
+		conf     => <<EOF
+LABEL, BUS="scsi", vendor="IBM-ESXS", NAME="1/2/a/b/node", SYMLINK="1/2/c/d/symlink"
 EOF
 	},
 );
@@ -238,7 +274,8 @@ foreach my $config (@tests) {
 	}
 
 	udev("remove", $config->{subsys}, $config->{devpath}, \$config->{conf});
-	if (-e "$PWD/$udev_root$config->{expected}") {
+	if ((-e "$PWD/$udev_root$config->{expected}") ||
+	    (-l "$PWD/$udev_root$config->{expected}")) {
 		print "remove: error\n\n";
 		system("tree $udev_root");
 		$error++;

udev-add.c

@@ -72,6 +72,34 @@ exit:
 	return retval;
 }
 
+static int create_path(char *file)
+{
+	char p[NAME_SIZE];
+	char *pos;
+	int retval;
+	struct stat stats;
+	
+	strncpy(p, file, sizeof(p));
+	pos = strchr(p+1, '/');
+	while (1) {
+		pos = strchr(pos+1, '/');
+		if (pos == NULL)
+			break;
+		*pos = 0x00;
+		if (stat(p, &stats)) {
+			retval = mkdir(p, 0755);
+			if (retval) {
+				dbg("mkdir(%s) failed with error '%s'",
+				    p, strerror(errno));
+				return retval;
+			}
+			dbg("created '%s'", p);
+		}
+		*pos = '/';
+	}
+	return 0;
+}
+
 /*
  * we possibly want to add some symlinks here
  * only numeric owner/group id's are supported
@@ -79,10 +107,14 @@ exit:
 static int create_node(struct udevice *dev)
 {
 	char filename[255];
+	char linktarget[255];
 	int retval = 0;
 	uid_t uid = 0;
 	gid_t gid = 0;
 	dev_t res;
+	int i;
+	int tail;
+
 
 	strncpy(filename, udev_root, sizeof(filename));
 	strncat(filename, dev->name, sizeof(filename));
@@ -109,31 +141,9 @@ static int create_node(struct udevice *dev)
 		return -EINVAL;
 	}
 
-	/* create subdirectories if requested */
+	/* create parent directories if needed */
-	if (strchr(dev->name, '/')) {
+	if (strrchr(dev->name, '/'))
-		char path[255];
+		create_path(filename);
-		char *pos;
-		struct stat stats;
-
-		strncpy(path, filename, sizeof(path));
-		pos = strchr(path+1, '/');
-		while (1) {
-			pos = strchr(pos+1, '/');
-			if (pos == NULL)
-				break;
-			*pos = 0x00;
-			if (stat(path, &stats)) {
-				retval = mkdir(path, 0755);
-				if (retval) {
-					dbg("mkdir(%s) failed with error '%s'",
-					    path, strerror(errno));
-					return retval;
-				}
-				dbg("created '%s'", path);
-			}
-			*pos = '/';
-		}
-	}
 
 	dbg("mknod(%s, %#o, %u, %u)", filename, dev->mode, dev->major, dev->minor);
 	retval = mknod(filename, dev->mode, res);
@@ -179,8 +189,43 @@ static int create_node(struct udevice *dev)
 		dbg("chown(%s, %u, %u)", filename, uid, gid);
 		retval = chown(filename, uid, gid);
 		if (retval)
-			dbg("chown(%s, %u, %u) failed with error '%s'", filename,
+			dbg("chown(%s, %u, %u) failed with error '%s'",
-			    uid, gid, strerror(errno));
+			    filename, uid, gid, strerror(errno));
+	}
+
+
+	/* create symlink if requested */
+	if (*dev->symlink) {
+		strncpy(filename, udev_root, sizeof(filename));
+		strncat(filename, dev->symlink, sizeof(filename));
+		dbg("symlink '%s' to node '%s' requested", filename, dev->name);
+		if (strrchr(dev->symlink, '/'))
+			create_path(filename);
+
+		/* optimize relative link */
+		linktarget[0] = '\0';
+		i = 0;
+		tail = 0;
+		while ((dev->name[i] == dev->symlink[i]) && dev->name[i]) {
+			if (dev->name[i] == '/')
+				tail = i+1;
+			i++;
+		}
+		while (dev->symlink[i]) {
+			if (dev->symlink[i] == '/')
+				strcat(linktarget, "../");
+			i++;
+		}
+
+		if (*linktarget == '\0')
+			strcpy(linktarget, "./");
+		strcat(linktarget, &dev->name[tail]);
+
+		dbg("symlink(%s, %s)", linktarget, filename);
+		retval = symlink(linktarget, filename);
+		if (retval)
+			dbg("symlink(%s, %s) failed with error '%s'",
+			    linktarget, filename, strerror(errno));
 	}
 
 	return retval;

udev-remove.c

@@ -34,47 +34,43 @@
 #include "udevdb.h"
 #include "libsysfs/libsysfs.h"
 
-
+static int delete_path(char *path)
-/*
- * Look up the sysfs path in the database to see if we have named this device
- * something different from the kernel name.  If we have, us it.  If not, use
- * the default kernel name for lack of anything else to know to do.
- */
-static char *get_name(char *path, int major, int minor)
 {
-	static char name[100];
+	char *pos;
-	struct udevice *dev;
+	int retval;
-	char *temp;
 
-	dev = udevdb_get_dev(path);
+	pos = strrchr(path, '/');
-	if (dev != NULL) {
+	while (1) {
-		strcpy(name, dev->name);
+		*pos = '\0';
-		goto exit;
+		pos = strrchr(path, '/');
+
+		/* don't remove the last one */
+		if ((pos == path) || (pos == NULL))
+			break;
+
+		/* remove if empty */
+		retval = rmdir(path);
+		if (retval) {
+			if (errno == ENOTEMPTY)
+				return 0;
+			dbg("rmdir(%s) failed with error '%s'",
+			    path, strerror(errno));
+			break;
+		}
+		dbg("removed '%s'", path);
 	}
-
+	return 0;
-	dbg("'%s' not found in database, falling back on default name", path);
-	temp = strrchr(path, '/');
-	if (temp == NULL)
-		return NULL;
-	strncpy(name, &temp[1], sizeof(name));
-
-exit:
-	dbg("name is '%s'", name);
-	return &name[0];
 }
 
-/*
+static int delete_node(struct udevice *dev)
- * We also want to clean up any symlinks that were created in create_node()
- */
-static int delete_node(char *name)
 {
 	char filename[255];
 	int retval;
 
 	strncpy(filename, udev_root, sizeof(filename));
-	strncat(filename, name, sizeof(filename));
+	strncat(filename, dev->name, sizeof(filename));
 
-	dbg("unlinking '%s'", filename);
+	dbg("unlinking node '%s'", filename);
 	retval = unlink(filename);
 	if (retval) {
 		dbg("unlink(%s) failed with error '%s'",
@@ -83,49 +79,48 @@ static int delete_node(char *name)
 	}
 
 	/* remove subdirectories */
-	if (strchr(name, '/')) {
+	if (strchr(dev->name, '/'))
-		char *pos;
+		delete_path(filename);
 
-		pos = strrchr(filename, '/');
+	if (*dev->symlink) {
-		while (1) {
+		strncpy(filename, udev_root, sizeof(filename));
-			*pos = 0x00;
+		strncat(filename, dev->symlink, sizeof(filename));
-			pos = strrchr(filename, '/');
+		dbg("unlinking symlink '%s'", filename);
-
+		retval = unlink(filename);
-			/* don't remove the last one */
+		if (retval) {
-			if ((pos == filename) || (pos == NULL))
+			dbg("unlink(%s) failed with error '%s'",
-				break;
+				filename, strerror(errno));
-
+			return retval;
-			/* remove if empty */
+		}
-			retval = rmdir(filename);
+		if (strchr(dev->symlink, '/')) {
-			if (retval) {
+			delete_path(filename);
-				if (errno == ENOTEMPTY)
-					return 0;
-				dbg("rmdir(%s) failed with error '%s'",
-				    filename, strerror(errno));
-				break;
-			}
-			dbg("removed '%s'", filename);
 		}
 	}
+
 	return retval;
 }
 
-int udev_remove_device(char *device, char *subsystem)
+/*
+ * Look up the sysfs path in the database to see if we have named this device
+ * something different from the kernel name.  If we have, us it.  If not, use
+ * the default kernel name for lack of anything else to know to do.
+ */
+int udev_remove_device(char *path, char *subsystem)
 {
-	char *name;
+	char name[100];
-	int retval = 0;
+	struct udevice *dev;
+	char *temp;
 
-	name = get_name(device, 0, 0);
+	dev = udevdb_get_dev(path);
-	if (name == NULL) {
+	if (dev == NULL) {
-		dbg ("get_name failed");
+		dbg("'%s' not found in database, falling back on default name", path);
-		retval = -ENODEV;
+		temp = strrchr(path, '/');
-		goto exit;
+		if (temp == NULL)
+			return -ENODEV;
+		strncpy(name, &temp[1], sizeof(name));
 	}
 
-	udevdb_delete_dev(device);
+	dbg("name is '%s'", dev->name);
-
+	udevdb_delete_dev(path);
-	return delete_node(name);
+	return delete_node(dev);
-
-exit:
-	return retval;
 }

udev.h

@@ -64,6 +64,7 @@ struct udevice {
 	int major;
 	int minor;
 	mode_t mode;
+	char symlink[NAME_SIZE];
 
 	/* fields that help us in building strings */
 	unsigned char bus_id[SYSFS_NAME_LEN];