[PATCH] udev - reverse user query options

Here we get the ability to query with the name of the node instead of
the device path. It uses a linear search over the whole database.

  kay@pim:~/src/udev.kay$ ./udev -q path -n video/webcam0
  /class/video4linux/video0


New version, with better function return codes for error handling.

4 files changed, 117 insertions, 40 deletions

diff --git a/udev.8 b/udev.8
index 0421fee4..ff89e435 100644
--- a/udev.8
+++ b/udev.8
@@ -50,10 +50,13 @@ will be prepended.
 .BI -q " query_type"
 Query the database for specified value of a created device node.
 Valid types are:
-.BR name ", " symlink ", " owner " or " group .
+.BR name ", " symlink ", " owner " , " group " or " path.
 .TP
 .BI -p " sysfs_path"
-Specify the sysfs path needed for the query.
+Specify the sysfs path of the device to query.
+.TP
+.BI -n " name"
+Specify the name of the node for the device to query.
 .TP
 .B -d
 Dump the whole database.
diff --git a/udev.c b/udev.c
index b872f424..3b701ac2 100644
--- a/udev.c
+++ b/udev.c
@@ -83,7 +83,8 @@ static inline char *get_seqnum(void)
 	return seqnum;
 }
 
-static void print_record(char *path, struct udevice *dev)
+/* callback for database dump */
+static int print_record(char *path, struct udevice *dev)
 {
 	printf("P: %s\n", path);
 	printf("N: %s\n", dev->name);
@@ -91,11 +92,13 @@ static void print_record(char *path, struct udevice *dev)
 	printf("O: %s\n", dev->owner);
 	printf("G: %s\n", dev->group);
 	printf("\n");
+	return 0;
 }
 
 enum query_type {
 	NONE,
 	NAME,
+	PATH,
 	SYMLINK,
 	OWNER,
 	GROUP
@@ -103,7 +106,7 @@ enum query_type {
 
 static inline int udev_user(int argc, char **argv)
 {
-	static const char short_options[] = "dp:q:rVh";
+	static const char short_options[] = "dn:p:q:rVh";
 	int option;
 	int retval = -EINVAL;
 	struct udevice dev;
@@ -111,6 +114,7 @@ static inline int udev_user(int argc, char **argv)
 	enum query_type query = NONE;
 	char result[NAME_SIZE] = "";
 	char path[NAME_SIZE] = "";
+	char name[NAME_SIZE] = "";
 
 	/* get command line options */
 	while (1) {
@@ -120,6 +124,11 @@ static inline int udev_user(int argc, char **argv)
 
 		dbg("option '%c'", option);
 		switch (option) {
+		case 'n':
+			dbg("udev name: %s\n", optarg);
+			strfieldcpy(name, optarg);
+			break;
+
 		case 'p':
 			dbg("udev path: %s\n", optarg);
 			strfieldcpy(path, optarg);
@@ -148,6 +157,11 @@ static inline int udev_user(int argc, char **argv)
 				break;
 			}
 
+			if (strcmp(optarg, "path") == 0) {
+				query = PATH;
+				break;
+			}
+
 			printf("unknown query type\n");
 			return -EINVAL;
 
@@ -161,7 +175,7 @@ static inline int udev_user(int argc, char **argv)
 				printf("unable to open udev database\n");
 				return -EACCES;
 			}
-			retval = udevdb_dump(print_record);
+			retval = udevdb_call_foreach(print_record);
 			udevdb_exit();
 			return retval;
 
@@ -179,44 +193,63 @@ static inline int udev_user(int argc, char **argv)
 
 	/* process options */
 	if (query != NONE) {
-		if (path[0] == '\0') {
-			printf("query needs device path specified\n");
-			return -EINVAL;
-		}
-
 		retval = udevdb_open_ro();
 		if (retval != 0) {
 			printf("unable to open udev database\n");
 			return -EACCES;
 		}
-		retval = udevdb_get_dev(path, &dev);
-		if (retval == 0) {
-			switch(query) {
-			case NAME:
-				if (root)
+
+		if (path[0] != '\0') {
+			retval = udevdb_get_dev(path, &dev);
+			if (retval != 0) {
+				printf("device not found in database\n");
+				goto exit;
+			}
+			goto print;
+		}
+
+		if (name[0] != '\0') {
+			retval = udevdb_get_dev_byname(name, path, &dev);
+			if (retval != 0) {
+				printf("device not found in database\n");
+				goto exit;
+			}
+			goto print;
+		}
+
+		printf("query needs device path(-p) or node name(-n) specified\n");
+		goto exit;
+
+print:
+		switch(query) {
+		case NAME:
+			if (root)
 				strfieldcpy(result, udev_root);
-				strncat(result, dev.name, sizeof(result));
-				break;
+			strncat(result, dev.name, sizeof(result));
+			break;
 
-			case SYMLINK:
-				strfieldcpy(result, dev.symlink);
-				break;
+		case SYMLINK:
+			strfieldcpy(result, dev.symlink);
+			break;
 
-			case GROUP:
-				strfieldcpy(result, dev.group);
-				break;
+		case GROUP:
+			strfieldcpy(result, dev.group);
+			break;
 
-			case OWNER:
-				strfieldcpy(result, dev.owner);
-				break;
+		case OWNER:
+			strfieldcpy(result, dev.owner);
+			break;
 
-			default:
-				break;
-			}
-			printf("%s\n", result);
-		} else {
-			printf("device not found in udev database\n");
+		case PATH:
+			strfieldcpy(result, path);
+			break;
+
+		default:
+			goto exit;
 		}
+		printf("%s\n", result);
+
+exit:
 		udevdb_exit();
 		return retval;
 	}
@@ -227,13 +260,16 @@ static inline int udev_user(int argc, char **argv)
 	}
 
 help:
-	printf("Usage: [-pqrdVh]\n"
+	printf("Usage: [-npqrdVh]\n"
 	       "  -q TYPE  query database for the specified value:\n"
 	       "             'name'    name of device node\n"
 	       "             'symlink' pointing to node\n"
 	       "             'owner'   of node\n"
 	       "             'group'   of node\n"
+	       "             'path'    sysfs device path\n"
 	       "  -p PATH  sysfs device path used for query\n"
+	       "  -n NAME  node name used for query\n"
+	       "\n"
 	       "  -r       print udev root\n"
 	       "  -d       dump whole database\n"
 	       "  -V       print udev version\n"
diff --git a/udevdb.c b/udevdb.c
index 2d99f51d..c4e064fc 100644
--- a/udevdb.c
+++ b/udevdb.c
@@ -143,25 +143,62 @@ int udevdb_open_ro(void)
 	return 0;
 }
 
-void (*user_record_callback) (char *path, struct udevice *dev);
+static int (*user_record_callback) (char *path, struct udevice *dev);
 
 static int traverse_callback(TDB_CONTEXT *tdb, TDB_DATA key, TDB_DATA dbuf, void *state)
 {
-	user_record_callback((char*) key.dptr, (struct udevice*) dbuf.dptr);
-	return 0;
+	return user_record_callback((char*) key.dptr, (struct udevice*) dbuf.dptr);
 }
 
 /**
- * udevdb_dump: dumps whole database by passing record data to user function
+ * udevdb_call_foreach: dumps whole database by passing record data to user function
  * @user_record_handler: user function called for every record in the database
  */
-int udevdb_dump(void (*user_record_handler) (char *path, struct udevice *dev))
+int udevdb_call_foreach(int (*user_record_handler) (char *path, struct udevice *dev))
 {
+	int retval = 0;
+
 	if (user_record_handler == NULL) {
 		dbg("invalid user record handling function");
 		return -EINVAL;
 	}
 	user_record_callback = user_record_handler;
-	tdb_traverse(udevdb, traverse_callback, NULL);
+	retval = tdb_traverse(udevdb, traverse_callback, NULL);
+	if (retval < 0)
+		return -ENODEV;
+	else
+		return 0;
+}
+
+static struct udevice *find_dev;
+static char *find_path;
+static const char *find_name;
+static int find_found;
+
+static int find_device_by_name(char *path, struct udevice *dev)
+{
+	if (strncmp(dev->name, find_name, sizeof(dev->name)) == 0) {
+		memcpy(find_dev, dev, sizeof(*find_dev));
+		strncpy(find_path, path, NAME_SIZE);
+		find_found = 1;
+		/* stop search */
+		return 1;
+	}
 	return 0;
 }
+
+/**
+ * udevdb_get_dev_byname: search device with given name by traversing the whole database
+ */
+int udevdb_get_dev_byname(const char *name, char *path, struct udevice *dev)
+{
+	find_found = 0;
+	find_path = path;
+	find_dev = dev;
+	find_name = name;
+	udevdb_call_foreach(find_device_by_name);
+	if (find_found == 1)
+		return 0;
+	else
+		return -1;
+}
diff --git a/udevdb.h b/udevdb.h
index a0e53382..6eaeb256 100644
--- a/udevdb.h
+++ b/udevdb.h
@@ -12,10 +12,11 @@
 extern void udevdb_exit(void);
 extern int udevdb_init(int init_flag);
 extern int udevdb_open_ro(void);
-extern int udevdb_dump(void (*user_record_handler) (char *path, struct udevice *dev));
+extern int udevdb_call_foreach(int (*user_record_handler) (char *path, struct udevice *dev));
 
 extern int udevdb_add_dev(const char *path, const struct udevice *dev);
 extern int udevdb_get_dev(const char *path, struct udevice *dev);
 extern int udevdb_delete_dev(const char *path);
+extern int udevdb_get_dev_byname(const char *name, char *path, struct udevice *dev);
 
 #endif /* _UDEVDB_H_ */