X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=blobdiff_plain;f=libsysfs%2Fsysfs_class.c;h=a132bb64cbc097a989e52a8ddeeeda2bdf69ddaa;hb=83e1f809c93c5d3770504e13ed06041af8252d20;hp=cb6ca9d00d6405bf2c534ba9b8ad94e91de18a91;hpb=fe3fe3b29ffbc7d0ce7dca6a371da31d8b3ff7f8;p=elogind.git

diff --git a/libsysfs/sysfs_class.c b/libsysfs/sysfs_class.c
index cb6ca9d00..a132bb64c 100644
--- a/libsysfs/sysfs_class.c
+++ b/libsysfs/sysfs_class.c
@@ -23,7 +23,7 @@
 #include "libsysfs.h"
 #include "sysfs.h"
 
-void sysfs_close_cls_dev(void *dev)
+static void sysfs_close_cls_dev(void *dev)
 {
 	sysfs_close_class_device((struct sysfs_class_device *)dev);
 }
@@ -38,8 +38,7 @@ static int class_name_equal(void *a, void *b)
 	if (a == NULL || b == NULL)
 		return 0;
 
-	if (strcmp(((unsigned char *)a), ((struct sysfs_class_device *)b)->name)
-		== 0)
+	if (strcmp(((char *)a), ((struct sysfs_class_device *)b)->name) == 0)
 		return 1;
 
 	return 0;
@@ -58,13 +57,15 @@ void sysfs_close_class_device(struct sysfs_class_device *dev)
 			sysfs_close_device(dev->sysdevice);
 		if (dev->driver != NULL)
 			sysfs_close_driver(dev->driver);
+		if (dev->parent != NULL)
+			sysfs_close_class_device(dev->parent);
 		free(dev);
 	}
 }
 
 /**
  * sysfs_close_class: close single class
- * @class: class structure
+ * @cls: class structure
  */
 void sysfs_close_class(struct sysfs_class *cls)
 {
@@ -96,61 +97,54 @@ static struct sysfs_class *alloc_class(void)
 	return (struct sysfs_class *)calloc(1, sizeof(struct sysfs_class));
 }
 
-/**
- * open_class_dir: opens up sysfs class directory
- * returns sysfs_directory struct with success and NULL with error
+/** 
+ * set_classdev_classname: Grabs classname from path
+ * @cdev: class device to set
+ * Returns nothing
  */
-static struct sysfs_directory *open_class_dir(const unsigned char *name)
+static void set_classdev_classname(struct sysfs_class_device *cdev)
 {
-	struct sysfs_directory *classdir = NULL;
-	unsigned char classpath[SYSFS_PATH_MAX];
-
-	if (name == NULL) {
-		errno = EINVAL;
-		return NULL;
-	}
-
-	memset(classpath, 0, SYSFS_PATH_MAX);
-	if ((sysfs_get_mnt_path(classpath, SYSFS_PATH_MAX)) != 0) {
-		dprintf("Sysfs not supported on this system\n");
-		return NULL;
-	}
-
-	strcat(classpath, SYSFS_CLASS_DIR);
-	strcat(classpath, "/");
-	strcat(classpath, name);
-	classdir = sysfs_open_directory(classpath);
-	if (classdir == NULL) {
-		errno = EINVAL;
-		dprintf("Class %s not supported on this system\n", name);
-		return NULL;
-	}
-	if ((sysfs_read_directory(classdir)) != 0) {
-		dprintf("Error reading %s class dir %s\n", name, classpath);
-		sysfs_close_directory(classdir);
-		return NULL;
+	char *c = NULL, *e = NULL;
+	int count = 0;
+
+	c = strstr(cdev->path, SYSFS_CLASS_NAME);
+	if (c == NULL) {
+		c = strstr(cdev->path, SYSFS_BLOCK_NAME);
+	} else {
+		c = strstr(c, "/");
+	}
+
+	if (c == NULL)
+		safestrcpy(cdev->classname, SYSFS_UNKNOWN);
+	else {
+		if (*c == '/')
+			c++;
+		e = c;
+		while (e != NULL && *e != '/' && *e != '\0') {
+			e++;
+			count++;
+		}
+		strncpy(cdev->classname, c, count);
 	}
-
-	return classdir;
 }
 
 /**
- * sysfs_open_class_device: Opens and populates class device
+ * sysfs_open_class_device_path: Opens and populates class device
  * @path: path to class device.
  * returns struct sysfs_class_device with success and NULL with error.
  */
-struct sysfs_class_device *sysfs_open_class_device(const unsigned char *path)
+struct sysfs_class_device *sysfs_open_class_device_path(const char *path)
 {
 	struct sysfs_class_device *cdev = NULL;
-	struct sysfs_directory *dir = NULL;
-	struct sysfs_link *curl = NULL;
-	struct sysfs_device *sdev = NULL;
-	struct sysfs_driver *drv = NULL;
 
 	if (path == NULL) {
 		errno = EINVAL;
 		return NULL;
 	}
+	if ((sysfs_path_is_dir(path)) != 0) {
+		dprintf("%s is not a valid path to a class device\n", path);
+		return NULL;
+	}
 	cdev = alloc_class_device();
 	if (cdev == NULL) {
 		dprintf("calloc failed\n");
@@ -158,131 +152,119 @@ struct sysfs_class_device *sysfs_open_class_device(const unsigned char *path)
 	}
 	if ((sysfs_get_name_from_path(path, cdev->name, SYSFS_NAME_LEN)) != 0) {
 		errno = EINVAL;
-		dprintf("Invalid class device path %s\n", path);
+		dprintf("Error getting class device name\n");
 		sysfs_close_class_device(cdev);
 		return NULL;
 	}
 
-	dir = sysfs_open_directory(path);
-	if (dir == NULL) {
-		dprintf("Error opening class device at %s\n", path);
-		sysfs_close_class_device(cdev);
-		return NULL;
-	}
-	if ((sysfs_read_directory(dir)) != 0) {
-		dprintf("Error reading class device at %s\n", path);
-		sysfs_close_directory(dir);
+	safestrcpy(cdev->path, path);
+	if ((sysfs_remove_trailing_slash(cdev->path)) != 0) {
+		dprintf("Invalid path to class device %s\n", cdev->path);
 		sysfs_close_class_device(cdev);
 		return NULL;
 	}
-	sysfs_read_all_subdirs(dir);
-	cdev->directory = dir;
-	strcpy(cdev->path, dir->path);
-
-	/* get driver and device, if implemented */
-	if (cdev->directory->links != NULL) {
-		dlist_for_each_data(cdev->directory->links, curl,
-				struct sysfs_link) {
-			if (strncmp(curl->name, SYSFS_DEVICES_NAME, 6) == 0) {
-				sdev = sysfs_open_device(curl->target);
-				if (sdev != NULL) {
-					cdev->sysdevice = sdev;
-					if (cdev->driver != NULL) 
-						strncpy(sdev->driver_name,
-							cdev->driver->name, 
-							SYSFS_NAME_LEN);
-				}
-			} else if (strncmp(curl->name, 
-						SYSFS_DRIVERS_NAME, 6) == 0) {
-				drv = sysfs_open_driver(curl->target);
-				if (drv != NULL) {
-					cdev->driver = drv;
-					if (cdev->sysdevice != NULL) {
-						strncpy(cdev->sysdevice->name,
-								drv->name, 
-								SYSFS_NAME_LEN);
-						if (drv->devices == NULL)
-							drv->devices = 
-								dlist_new
-								(sizeof(struct 
-								sysfs_device));
-						dlist_unshift(drv->devices, 
-							cdev->sysdevice);
-					}
-				}
-			}
-		}
-	}
+	set_classdev_classname(cdev);
+
 	return cdev;
 }
 
 /**
- * get_all_class_devices: gets all devices for class
- * @class: class to get devices for
- * returns 0 with success and -1 with failure
+ * sysfs_get_class_devices: gets all devices for class
+ * @cls: class to get devices for
+ * returns dlist of class_devices with success and NULL with error
  */
-static int get_all_class_devices(struct sysfs_class *cls)
+struct dlist *sysfs_get_class_devices(struct sysfs_class *cls)
 {
 	struct sysfs_class_device *dev = NULL;
 	struct sysfs_directory *cur = NULL;
 
-	if (cls == NULL || cls->directory == NULL) {
+	if (cls == NULL) {
 		errno = EINVAL;
-		return -1;
+		return NULL;
 	}
-	if (cls->directory->subdirs == NULL)
-		return 0;
-	dlist_for_each_data(cls->directory->subdirs, cur, 
-			struct sysfs_directory) {
-		dev = sysfs_open_class_device(cur->path);
-		if (dev == NULL) {
-			dprintf("Error opening device at %s\n",	cur->path);
-			continue;
-		}
-		if (cls->devices == NULL)
-			cls->devices = dlist_new_with_delete
+
+	if (cls->devices != NULL) 
+		return cls->devices;
+
+	if (cls->directory == NULL) {
+		cls->directory = sysfs_open_directory(cls->path);
+		if (cls->directory == NULL) 
+			return NULL;
+	}
+
+	if ((sysfs_read_dir_subdirs(cls->directory)) != 0) 
+		return NULL;
+
+	if (cls->directory->subdirs != NULL) {
+		dlist_for_each_data(cls->directory->subdirs, cur, 
+						struct sysfs_directory) {
+			dev = sysfs_open_class_device_path(cur->path);
+			if (dev == NULL) {
+				dprintf("Error opening device at %s\n",	
+								cur->path);
+				continue;
+			}
+			if (cls->devices == NULL)
+				cls->devices = dlist_new_with_delete
 					(sizeof(struct sysfs_class_device),
 					 		sysfs_close_cls_dev);
-		dlist_unshift(cls->devices, dev);
+			dlist_unshift_sorted(cls->devices, dev, sort_list);
+		}
 	}
-	return 0;
+	return cls->devices;
 }
 
 /**
  * sysfs_open_class: opens specific class and all its devices on system
  * returns sysfs_class structure with success or NULL with error.
  */
-struct sysfs_class *sysfs_open_class(const unsigned char *name)
+struct sysfs_class *sysfs_open_class(const char *name)
 {
 	struct sysfs_class *cls = NULL;
-	struct sysfs_directory *classdir = NULL;
+	char classpath[SYSFS_PATH_MAX];
 
 	if (name == NULL) {
 		errno = EINVAL;
 		return NULL;
 	}
 
+	memset(classpath, 0, SYSFS_PATH_MAX);
+        if ((sysfs_get_mnt_path(classpath, SYSFS_PATH_MAX)) != 0) {
+                dprintf("Sysfs not supported on this system\n");
+                return NULL;
+        }
+
+	/* 
+	 * We shall now treat "block" also as a class. Hence, check here
+	 * if "name" is "block" and proceed accordingly
+	 */
+	if (strcmp(name, SYSFS_BLOCK_NAME) == 0) {
+		safestrcat(classpath, "/");
+		safestrcat(classpath, SYSFS_BLOCK_NAME);
+	} else {
+		safestrcat(classpath, "/");
+		safestrcat(classpath, SYSFS_CLASS_NAME);
+		safestrcat(classpath, "/");
+		safestrcat(classpath, name);
+	}
+	if ((sysfs_path_is_dir(classpath)) != 0) {
+		dprintf("Class %s not found on the system\n", name);
+		return NULL;
+	}
+
 	cls = alloc_class();
 	if (cls == NULL) {
 		dprintf("calloc failed\n");
 		return NULL;
 	}
-	strcpy(cls->name, name);	
-	classdir = open_class_dir(name);
-	if (classdir == NULL) {
-		dprintf("Invalid class, %s not supported on this system\n",
-			name);
-		sysfs_close_class(cls);
-		return NULL;
-	}
-	cls->directory = classdir;
-	strcpy(cls->path, classdir->path);
-	if ((get_all_class_devices(cls)) != 0) {
-		dprintf("Error reading %s class devices\n", name);
+	safestrcpy(cls->name, name);	
+	safestrcpy(cls->path, classpath);
+	if ((sysfs_remove_trailing_slash(cls->path)) != 0) {
+		dprintf("Invalid path to class device %s\n", cls->path);
 		sysfs_close_class(cls);
 		return NULL;
 	}
-
+	
 	return cls;
 }
 
@@ -291,59 +273,290 @@ struct sysfs_class *sysfs_open_class(const unsigned char *name)
  * @class: class to find device on
  * @name: class name of the device
  */ 
-struct sysfs_class_device *sysfs_get_class_device(struct sysfs_class *class,
-					unsigned char *name)
+struct sysfs_class_device *sysfs_get_class_device(struct sysfs_class *cls,
+					char *name)
 {
-	if (class == NULL || name == NULL) {
+	if (cls == NULL || name == NULL) {
 		errno = EINVAL;
 		return NULL;
 	}
 
-	return (struct sysfs_class_device *)dlist_find_custom(class->devices,
+	if (cls->devices == NULL) {
+		cls->devices = sysfs_get_class_devices(cls);
+		if (cls->devices == NULL) 
+			return NULL;
+	}
+	return (struct sysfs_class_device *)dlist_find_custom(cls->devices,
 			name, class_name_equal);
 }
 
 /**
- * sysfs_open_class_device_by_name: Locates a specific class_device and returns it.
+ * sysfs_get_classdev_device: returns the sysfs_device corresponding to
+ * 		sysfs_class_device, if present
+ * @clsdev: class device whose sysfs_device is required
+ * Returns sysfs_device on success, NULL on error or if device is not
+ * implemented
+ */ 
+struct sysfs_device *sysfs_get_classdev_device
+			(struct sysfs_class_device *clsdev)
+{
+	struct sysfs_link *devlink = NULL;
+	char devpath[SYSFS_PATH_MAX];
+	
+	if (clsdev == NULL) {
+		errno = EINVAL;
+		return NULL;
+	}
+	safestrcpy(devpath, clsdev->path);
+	safestrcat(devpath, "/device");
+	if ((sysfs_path_is_link(devpath)) != 0) {
+		if (clsdev->sysdevice != NULL) {
+			sysfs_close_device(clsdev->sysdevice);
+			clsdev->sysdevice = NULL;
+		}
+		return NULL;
+	}
+	
+	if (clsdev->directory == NULL) {
+		clsdev->directory = sysfs_open_directory(clsdev->path);
+		if (clsdev->directory == NULL)
+			return NULL;
+	}
+	devlink = sysfs_get_directory_link(clsdev->directory, "device");
+	if (devlink == NULL) {
+		if (clsdev->sysdevice != NULL) {
+			dprintf("Device link no longer exists\n");
+			sysfs_close_device(clsdev->sysdevice);
+			clsdev->sysdevice = NULL;
+		}
+		return NULL;
+	}
+
+	if (clsdev->sysdevice != NULL) {
+		if (!strncmp(devlink->target, clsdev->sysdevice->path,
+						SYSFS_PATH_MAX)) 
+			/* sysdevice hasn't changed */
+			return (clsdev->sysdevice);
+		else 
+			/* come here only if the device link for has changed */
+			sysfs_close_device(clsdev->sysdevice);
+	}
+
+	clsdev->sysdevice = sysfs_open_device_path(devlink->target);
+	if (clsdev->sysdevice == NULL)
+		return NULL;
+
+	return (clsdev->sysdevice);
+}
+				
+/**
+ * sysfs_get_classdev_driver: returns the sysfs_driver corresponding to
+ * 		sysfs_class_device, if present
+ * @clsdev: class device whose sysfs_device is required
+ * Returns sysfs_driver on success, NULL on error or if driver is not
+ * implemented
+ */ 
+struct sysfs_driver *sysfs_get_classdev_driver
+			(struct sysfs_class_device *clsdev)
+{
+	struct sysfs_link *drvlink = NULL;
+	char drvpath[SYSFS_PATH_MAX];
+	
+	if (clsdev == NULL) {
+		errno = EINVAL;
+		return NULL;
+	}
+ 	safestrcpy(drvpath, clsdev->path);
+	safestrcat(drvpath, "/driver");
+	if ((sysfs_path_is_link(drvpath)) != 0) {
+		if (clsdev->driver != NULL) {
+			sysfs_close_driver(clsdev->driver);
+			clsdev->driver = NULL;
+		}
+		return NULL;
+	}
+	 
+	if (clsdev->directory == NULL) {
+		clsdev->directory = sysfs_open_directory(clsdev->path);
+		if (clsdev->directory == NULL)
+			return NULL;
+	}
+	drvlink = sysfs_get_directory_link(clsdev->directory, "driver");
+	if (drvlink == NULL) {
+		if (clsdev->driver != NULL) {
+			dprintf("Driver link no longer exists\n");
+			sysfs_close_driver(clsdev->driver);
+			clsdev->driver = NULL;
+		}
+		return NULL;
+	}
+	if (clsdev->driver != NULL) {
+		if (!strncmp(drvlink->target, clsdev->driver->path,
+	      						SYSFS_PATH_MAX))
+			/* driver hasn't changed */
+	 		return (clsdev->driver);
+ 		else
+			/* come here only if the device link for has changed */
+			sysfs_close_driver(clsdev->driver);
+	}
+		
+	clsdev->driver = sysfs_open_driver_path(drvlink->target);
+	if (clsdev->driver == NULL)
+		return NULL;
+
+	return (clsdev->driver);
+}
+
+/** 
+ * get_blockdev_parent: Get the parent class device for a "block" subsystem 
+ * 		device if present
+ * @clsdev: block subsystem class device whose parent needs to be found
+ * Returns 0 on success and 1 on error
+ */
+static int get_blockdev_parent(struct sysfs_class_device *clsdev)
+{
+	char parent_path[SYSFS_PATH_MAX], *c = NULL;
+
+	safestrcpy(parent_path, clsdev->path);
+	c = strstr(parent_path, SYSFS_BLOCK_NAME);
+	if (c == NULL) {
+		dprintf("Class device %s does not belong to BLOCK subsystem\n",
+				clsdev->name);
+		return 1;
+	}
+	c += strlen(SYSFS_BLOCK_NAME);
+	if (*c == '/')
+		c++;
+	else
+		goto errout;
+
+       /* validate whether the given class device is a partition or not */
+        if ((strncmp(c, clsdev->name, strlen(clsdev->name))) == 0) {
+                dprintf("%s not a partition\n", clsdev->name);
+                return 1;
+        }
+		      
+      	c = strchr(c, '/');
+	if (c == NULL)
+		goto errout;
+
+	*c = '\0';
+					
+	clsdev->parent = sysfs_open_class_device_path(parent_path);
+	if (clsdev->parent == NULL) {
+		dprintf("Error opening the parent class device at %s\n", 
+								parent_path);
+		return 1;
+	}
+	return 0;
+
+errout:
+	dprintf("Invalid path %s\n", clsdev->path);
+	return 1;
+}
+
+/**
+ * sysfs_get_classdev_parent: Retrieves the parent of a class device. 
+ * 	eg., when working with hda1, this function can be used to retrieve the
+ * 		sysfs_class_device for hda
+ * 		
+ * @clsdev: class device whose parent details are required.
+ * Returns sysfs_class_device of the parent on success, NULL on failure
+ */ 
+struct sysfs_class_device *sysfs_get_classdev_parent
+				(struct sysfs_class_device *clsdev)
+{
+	if (clsdev == NULL) {
+		errno = EINVAL;
+		return NULL;
+	}
+	if (clsdev->parent != NULL)
+		return (clsdev->parent);
+	
+	/* 
+	 * As of now, only block devices have a parent child heirarchy in sysfs
+	 * We do not know, if, in the future, more classes will have a similar
+	 * structure. Hence, we now call a specialized function for block and
+	 * later we can add support functions for other subsystems as required.
+	 */ 
+	if (!(strncmp(clsdev->classname, SYSFS_BLOCK_NAME, 
+					sizeof(SYSFS_BLOCK_NAME)))) {
+		if ((get_blockdev_parent(clsdev)) == 0) 
+			return (clsdev->parent);
+	}
+	return NULL;
+}
+
+/**
+ * get_classdev_path: given the class and a device in the class, return the
+ * 		absolute path to the device
+ * @classname: name of the class
+ * @clsdev: the class device
+ * @path: buffer to return path
+ * @psize: size of "path"
+ * Returns 0 on SUCCESS or -1 on error
+ */
+static int get_classdev_path(const char *classname, const char *clsdev, 
+		char *path, size_t len)
+{
+	if (classname == NULL || clsdev == NULL || path == NULL) {
+		errno = EINVAL;
+		return -1;
+	}
+        if (sysfs_get_mnt_path(path, len) != 0) {
+                dprintf("Error getting sysfs mount path\n");
+                return -1;
+	}
+	if (strncmp(classname, SYSFS_BLOCK_NAME,
+				sizeof(SYSFS_BLOCK_NAME)) == 0) {
+		safestrcatmax(path, "/", len);
+		safestrcatmax(path, SYSFS_BLOCK_NAME, len);
+	} else {
+		safestrcatmax(path, "/", len);
+		safestrcatmax(path, SYSFS_CLASS_NAME, len);
+		safestrcatmax(path, "/", len);
+		safestrcatmax(path, classname, len);
+	}
+	safestrcatmax(path, "/", len);
+	safestrcatmax(path, clsdev, len);
+	return 0;
+}
+
+/**
+ * sysfs_open_class_device: Locates a specific class_device and returns it.
  * Class_device must be closed using sysfs_close_class_device
  * @classname: Class to search
  * @name: name of the class_device
+ * 
+ * NOTE:
+ * 	Call sysfs_close_class_device() to close the class device
  */
-struct sysfs_class_device *sysfs_open_class_device_by_name
-		(const unsigned char *classname, unsigned char *name)
+struct sysfs_class_device *sysfs_open_class_device
+		(const char *classname, const char *name)
 {
-	struct sysfs_class *class = NULL;
-	struct sysfs_class_device *cdev = NULL, *rcdev = NULL;
+	char devpath[SYSFS_PATH_MAX];
+	struct sysfs_class_device *cdev = NULL;
 
 	if (classname == NULL || name == NULL) {
 		errno = EINVAL;
 		return NULL;
 	}
 	
-	class = sysfs_open_class(classname);
-	if (class == NULL) {
-		dprintf("Error opening class %s\n", classname);
+	memset(devpath, 0, SYSFS_PATH_MAX);
+	if ((get_classdev_path(classname, name, devpath, 
+					SYSFS_PATH_MAX)) != 0) {
+		dprintf("Error getting to device %s on class %s\n",
+							name, classname);
 		return NULL;
 	}
-
-	cdev = sysfs_get_class_device(class, name);
+	
+	cdev = sysfs_open_class_device_path(devpath);
 	if (cdev == NULL) {
 		dprintf("Error getting class device %s from class %s\n",
 				name, classname);
-		sysfs_close_class(class);
-		return NULL;
-	}
-
-	rcdev = sysfs_open_class_device(cdev->directory->path);
-	if (rcdev == NULL) {
-		dprintf("Error getting class device %s from class %s\n",
-				name, classname);
-		sysfs_close_class(class);
 		return NULL;
 	}
-	sysfs_close_class(class);
-	
-	return rcdev;
+	return cdev;
 }
 
 /**
@@ -354,57 +567,47 @@ struct sysfs_class_device *sysfs_open_class_device_by_name
  */
 struct dlist *sysfs_get_classdev_attributes(struct sysfs_class_device *cdev)
 {
-	if (cdev == NULL || cdev->directory == NULL)
+	if (cdev == NULL)
 		return NULL;
 
+	if (cdev->directory == NULL) {
+		cdev->directory = sysfs_open_directory(cdev->path);
+		if (cdev->directory == NULL) 
+			return NULL;
+	}
+	if (cdev->directory->attributes == NULL) {
+		if ((sysfs_read_dir_attributes(cdev->directory)) != 0) 
+			return NULL;
+	}
 	return (cdev->directory->attributes);
 }
 
 /**
- * sysfs_find_device_class: locates the device the device is on
- * @bus_id: device to look for
- * @classname: buffer to copy class name to
- * @bsize: size of buffer
- * returns 0 with success and -1 with error
+ * sysfs_refresh_clsassdev_attributes: refreshes the driver's list of attributes
+ * @clsdev: sysfs_class_device whose attributes to refresh
+ *
+ * NOTE: Upon return, prior references to sysfs_attributes for this classdev
+ *              _may_ not be valid
+ *
+ * Returns list of attributes on success and NULL on failure
  */
-int sysfs_find_device_class(const unsigned char *bus_id, 
-				unsigned char *classname, size_t bsize)
+struct dlist *sysfs_refresh_classdev_attributes
+			(struct sysfs_class_device *clsdev)
 {
-	unsigned char class[SYSFS_NAME_LEN], clspath[SYSFS_NAME_LEN];
-	unsigned char *cls = NULL, *clsdev = NULL;
-	struct dlist *clslist = NULL, *clsdev_list = NULL;
-
-	if (bus_id == NULL || classname == NULL) {
+	if (clsdev == NULL) {
 		errno = EINVAL;
-		return -1;
+		return NULL;
 	}
 
-	strcpy(class, SYSFS_CLASS_DIR);
-	clslist = sysfs_open_subsystem_list(class);
-	if (clslist != NULL) {
-		dlist_for_each_data(clslist, cls, char) {
-			memset(clspath, 0, SYSFS_NAME_LEN);
-			strcpy(clspath, SYSFS_CLASS_DIR);
-			strcat(clspath, "/");
-			strcat(clspath, cls);
-			clsdev_list = sysfs_open_subsystem_list(clspath);
-			if (clsdev_list != NULL) {
-				dlist_for_each_data(clsdev_list, 
-							clsdev, char) {
-					if (strcmp(bus_id, clsdev) == 0) {
-						strncpy(classname, 
-								cls, bsize);
-						sysfs_close_list(clsdev_list);
-						sysfs_close_list(clslist);
-						return 0;
-					}
-				}
-				sysfs_close_list(clsdev_list);
-			}
-		}
-		sysfs_close_list(clslist);
+	if (clsdev->directory == NULL)
+		return (sysfs_get_classdev_attributes(clsdev));
+
+	if ((sysfs_refresh_dir_attributes(clsdev->directory)) != 0) {
+		dprintf("Error refreshing class_device attributes\n");
+		return NULL;
 	}
-	return -1;
+
+	return (clsdev->directory->attributes);
 }
 
 /**
@@ -414,118 +617,92 @@ int sysfs_find_device_class(const unsigned char *bus_id,
  * returns sysfs_attribute reference with success or NULL with error
  */
 struct sysfs_attribute *sysfs_get_classdev_attr
-		(struct sysfs_class_device *clsdev, const unsigned char *name)
+		(struct sysfs_class_device *clsdev, const char *name)
 {
 	struct sysfs_attribute *cur = NULL;
-
-	if (clsdev == NULL || clsdev->directory == NULL ||
-		clsdev->directory->attributes == NULL || name == NULL) {
+	struct sysfs_directory *sdir = NULL;
+	struct dlist *attrlist = NULL;
+	
+	if (clsdev == NULL || name == NULL) {
 		errno = EINVAL;
 		return NULL;
 	}
-
-	cur = sysfs_get_directory_attribute(clsdev->directory,
-						(unsigned char *)name);
-	if (cur != NULL)
-		return cur;
-
-	return NULL;
-}
-
-/**
- * sysfs_write_classdev_attr: modify writable attribute value for the given
- * 				class device
- * @dev: class device name for which the attribute has to be changed
- * @attrib: attribute to change
- * @value: value to change to
- * @len: size of buffer at "value"
- * Returns 0 on success and -1 on error
- */
-int sysfs_write_classdev_attr(unsigned char *dev, unsigned char *attrib,
-				unsigned char *value, size_t len)
-{
-	struct sysfs_class_device *clsdev = NULL;
-	struct sysfs_attribute *attribute = NULL;
-	unsigned char class_name[SYSFS_NAME_LEN];
-
-	if (dev == NULL || attrib == NULL || value == NULL) {
-		errno = EINVAL;
-		return -1;
-	}
 	
-	memset(class_name, 0, SYSFS_NAME_LEN);
-	if ((sysfs_find_device_class(dev, 
-					class_name, SYSFS_NAME_LEN)) < 0) {
-		dprintf("Class device %s not found\n", dev);
-		return -1;
-	}
-	clsdev = sysfs_open_class_device_by_name(class_name, dev);
-	if (clsdev == NULL) {
-		dprintf("Error opening %s in class %s\n", dev, class_name);
-		return -1;
-	}
-	attribute = sysfs_get_directory_attribute(clsdev->directory, attrib);
-	if (attribute == NULL) {
-		dprintf("Attribute %s not defined for device %s on class %s\n",
-				attrib, dev, class_name);
-		sysfs_close_class_device(clsdev);
-		return -1;
-	}
-	if ((sysfs_write_attribute(attribute, value, len)) < 0) {
-		dprintf("Error setting %s to %s\n", attrib, value);
-		sysfs_close_class_device(clsdev);
-		return -1;
+	/* 
+	 * First, see if it's in the current directory. Then look at 
+	 * subdirs since class devices can have subdirs of attributes.
+	 */ 
+	attrlist = sysfs_get_classdev_attributes(clsdev);
+	if (attrlist != NULL) {
+		cur = sysfs_get_directory_attribute(clsdev->directory,
+						(char *)name);
+		if (cur != NULL)
+			return cur;
+	}
+
+	if (clsdev->directory == NULL)
+		return NULL;
+
+	if (clsdev->directory->subdirs == NULL) 
+		if ((sysfs_read_dir_subdirs(clsdev->directory)) != 0 ||
+		    clsdev->directory->subdirs == NULL) 
+			return NULL;
+
+	if (clsdev->directory->subdirs != NULL) {
+		dlist_for_each_data(clsdev->directory->subdirs, sdir,
+						struct sysfs_directory) {
+			if ((sysfs_path_is_dir(sdir->path)) != 0) 
+				continue;
+			cur = sysfs_get_directory_attribute(sdir,
+							(char *)name);
+			if (cur == NULL)
+				continue;
+		}
 	}
-	sysfs_close_class_device(clsdev);
-	return 0;
+	return cur;
 }
 
 /**
- * sysfs_read_classdev_attr: read an attribute for a given class device
+ * sysfs_open_classdev_attr: read an attribute for a given class device
+ * @classname: name of the class on which to look
  * @dev: class device name for which the attribute has to be read
  * @attrib: attribute to read
- * @value: buffer to return value to user
- * @len: size of buffer at "value"
- * Returns 0 on success and -1 on error
+ * Returns sysfs_attribute * on SUCCESS and NULL on error
+ * 
+ * NOTE:
+ * 	A call to sysfs_close_attribute() is required to close the
+ * 	attribute returned and to free memory
  */
-int sysfs_read_classdev_attr(unsigned char *dev, unsigned char *attrib,
-				unsigned char *value, size_t len)
+struct sysfs_attribute *sysfs_open_classdev_attr(const char *classname,
+		const char *dev, const char *attrib)
 {
-	struct sysfs_class_device *clsdev = NULL;
 	struct sysfs_attribute *attribute = NULL;
-	unsigned char class_name[SYSFS_NAME_LEN];
+	char path[SYSFS_PATH_MAX];
 
-	if (dev == NULL || attrib == NULL || value == NULL) {
+	if (classname == NULL || dev == NULL || attrib == NULL) {
 		errno = EINVAL;
-		return -1;
-	}
-	
-	memset(class_name, 0, SYSFS_NAME_LEN);
-	if ((sysfs_find_device_class(dev, 
-					class_name, SYSFS_NAME_LEN)) < 0) {
-		dprintf("Class device %s not found\n", dev);
-		return -1;
+		return NULL;
 	}
-	clsdev = sysfs_open_class_device_by_name(class_name, dev);
-	if (clsdev == NULL) {
-		dprintf("Error opening %s in class %s\n", dev, class_name);
-		return -1;
+	memset(path, 0, SYSFS_PATH_MAX);
+	if ((get_classdev_path(classname, dev, path, SYSFS_PATH_MAX)) != 0) {
+		dprintf("Error getting to device %s on class %s\n",
+						dev, classname);
+		return NULL;
 	}
-	attribute = sysfs_get_directory_attribute(clsdev->directory, attrib);
+	safestrcat(path, "/");
+	safestrcat(path, attrib);
+	attribute = sysfs_open_attribute(path);
 	if (attribute == NULL) {
-		dprintf("Attribute %s not defined for device %s on class %s\n",
-				attrib, dev, class_name);
-		sysfs_close_class_device(clsdev);
-		return -1;
+		dprintf("Error opening attribute %s on class device %s\n",
+				attrib, dev);
+		return NULL;
 	}
-	if (attribute->len > len) {
-		dprintf("Value length %d is greater that suppled buffer %d\n",
-				attribute->len, len);
-		sysfs_close_class_device(clsdev);
-		return -1;
+	if ((sysfs_read_attribute(attribute)) != 0) {
+		dprintf("Error reading attribute %s for class device %s\n",
+				attrib, dev);
+		sysfs_close_attribute(attribute);
+		return NULL;
 	}
-	strncpy(value, attribute->value, attribute->len);
-	value[(attribute->len)+1] = 0;
-	sysfs_close_class_device(clsdev);
-	return 0;
+	return attribute;
 }
+