From: dsteklof@us.ibm.com <dsteklof@us.ibm.com>
Date: Tue, 25 Nov 2003 07:47:43 +0000 (-0800)
Subject: [PATCH] libsysfs changes for sysfsutils 0.3.0
X-Git-Tag: 008~33
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ff44a6b0b7e98c9f696ee13c197d982819991de8;p=systemd

[PATCH] libsysfs changes for sysfsutils 0.3.0

Here's the patch to up the library to the sysfsutils-0_3_0 level. The
following changes:

1) adds class name to sysfs_class_device structure
2) adds bus to sysfs_device
3) gets rid of code that made assumptions as to bus addresses being
unique across buses, which isn't the case.


I still owe you:

1) change getpagesize->sysconf. This is in the CVS tree and part of other
changes we're currently testing. Patch will follow.
2) you need a function to get a sysfs_class_device's parent. We hadn't
considered class devices to have parents, the one example of a multilevel
is the block class. We will add this function and send the patch to you.
---

diff --git a/libsysfs/libsysfs.h b/libsysfs/libsysfs.h
index b3ffc467..f7e989e2 100644
--- a/libsysfs/libsysfs.h
+++ b/libsysfs/libsysfs.h
@@ -32,8 +32,11 @@
 #define SYSFS_FSTYPE_NAME	"sysfs"
 #define SYSFS_PROC_MNTS		"/proc/mounts"
 #define SYSFS_BUS_DIR		"/bus"
+#define SYSFS_BUS_NAME		"bus"
 #define SYSFS_CLASS_DIR		"/class"
+#define SYSFS_CLASS_NAME	"class"
 #define SYSFS_BLOCK_DIR		"/block"
+#define SYSFS_BLOCK_NAME	"block"
 #define SYSFS_DEVICES_DIR	"/devices"
 #define SYSFS_DEVICES_NAME	"devices"
 #define SYSFS_DRIVERS_DIR	"/drivers"
@@ -42,10 +45,6 @@
 #define SYSFS_UNKNOWN		"unknown"
 #define SYSFS_PATH_ENV		"SYSFS_PATH"
 
-/* Some "block" subsystem specific #defines */
-#define SYSFS_QUEUE_NAME	"queue"
-#define SYSFS_IOSCHED_NAME	"iosched"
-
 #define SYSFS_PATH_MAX		255
 #define	SYSFS_NAME_LEN		50
 #define SYSFS_BUS_ID_SIZE	20
@@ -89,8 +88,9 @@ struct sysfs_device {
 	struct dlist *children;	
 	unsigned char name[SYSFS_NAME_LEN];
 	unsigned char bus_id[SYSFS_NAME_LEN];
-	unsigned char path[SYSFS_PATH_MAX];
+	unsigned char bus[SYSFS_NAME_LEN];
 	unsigned char driver_name[SYSFS_NAME_LEN];
+	unsigned char path[SYSFS_PATH_MAX];
 
 	/* for internal use only */
 	struct sysfs_directory *directory;	
@@ -119,6 +119,7 @@ struct sysfs_class_device {
 	struct sysfs_device *sysdevice;		/* NULL if virtual */
 	struct sysfs_driver *driver;		/* NULL if not implemented */
 	unsigned char name[SYSFS_NAME_LEN];
+	unsigned char classname[SYSFS_NAME_LEN];
 	unsigned char path[SYSFS_PATH_MAX];
 
 	/* for internal use only */
@@ -185,10 +186,8 @@ extern struct dlist *sysfs_get_driver_links(struct sysfs_driver *driver);
 extern void sysfs_close_driver_by_name(struct sysfs_driver *driver);
 extern struct sysfs_driver *sysfs_open_driver_by_name
 	(const unsigned char *drv_name, const unsigned char *bus, size_t bsize);
-extern int sysfs_write_driver_attr(unsigned char *drv, unsigned char *attrib,
-				unsigned char *value, size_t len);
-extern int sysfs_read_driver_attr(unsigned char *drv, unsigned char *attrib,
-				unsigned char *value, size_t len);
+extern struct sysfs_attribute *sysfs_open_driver_attr(const unsigned char *bus, 
+		const unsigned char *drv, const unsigned char *attrib);
 
 /* generic sysfs device access */
 extern void sysfs_close_root_device(struct sysfs_root_device *root);
@@ -201,10 +200,8 @@ extern struct sysfs_attribute *sysfs_get_device_attr
 extern struct dlist *sysfs_get_device_attributes(struct sysfs_device *device);
 extern struct sysfs_device *sysfs_open_device_by_id
 	(const unsigned char *bus_id, const unsigned char *bus, size_t bsize);
-extern int sysfs_write_device_attr(unsigned char *dev, unsigned char *attrib,
-				unsigned char *value, size_t len);
-extern int sysfs_read_device_attr(unsigned char *dev, unsigned char *attrib,
-				unsigned char *value, size_t len);
+extern struct sysfs_attribute *sysfs_open_device_attr(const unsigned char *bus, 
+		const unsigned char *bus_id, const unsigned char *attrib);
 
 /* generic sysfs bus access */
 extern void sysfs_close_bus(struct sysfs_bus *bus);
@@ -218,8 +215,6 @@ extern struct sysfs_attribute *sysfs_get_bus_attribute(struct sysfs_bus *bus,
 						unsigned char *attrname);
 extern struct sysfs_device *sysfs_open_bus_device(unsigned char *busname, 
 							unsigned char *dev_id);
-extern int sysfs_find_device_bus(const unsigned char *dev_id, 
-					unsigned char *busname,	size_t bsize);
 extern int sysfs_find_driver_bus(const unsigned char *driver, 
 					unsigned char *busname,	size_t bsize);
 
@@ -232,17 +227,14 @@ extern struct sysfs_class *sysfs_open_class(const unsigned char *name);
 extern struct sysfs_class_device *sysfs_get_class_device
 	(struct sysfs_class *class, unsigned char *name);
 extern struct sysfs_class_device *sysfs_open_class_device_by_name
-	(const unsigned char *class, unsigned char *name);
+	(const unsigned char *class, const unsigned char *name);
 extern struct dlist *sysfs_get_classdev_attributes
 	(struct sysfs_class_device *cdev);
-extern int sysfs_find_device_class(const unsigned char *bus_id, 
-		unsigned char *classname, size_t bsize);
 extern struct sysfs_attribute *sysfs_get_classdev_attr
 	(struct sysfs_class_device *clsdev, const unsigned char *name);
-extern int sysfs_write_classdev_attr(unsigned char *dev, unsigned char *attrib, 
-		unsigned char *value, size_t len);
-extern int sysfs_read_classdev_attr(unsigned char *dev, unsigned char *attrib, 
-		unsigned char *value, size_t len);
+extern struct sysfs_attribute *sysfs_open_classdev_attr
+	(const unsigned char *classname, const unsigned char *dev, 
+	 					const unsigned char *attrib); 
 
 #ifdef __cplusplus
 }
diff --git a/libsysfs/sysfs_bus.c b/libsysfs/sysfs_bus.c
index 19fc275d..3111154c 100644
--- a/libsysfs/sysfs_bus.c
+++ b/libsysfs/sysfs_bus.c
@@ -25,12 +25,12 @@
 
 static void sysfs_close_dev(void *dev)
 {
-	        sysfs_close_device((struct sysfs_device *)dev);
+        sysfs_close_device((struct sysfs_device *)dev);
 }
 
 static void sysfs_close_drv(void *drv)
 {
-	        sysfs_close_driver((struct sysfs_driver *)drv);
+        sysfs_close_driver((struct sysfs_driver *)drv);
 }
 
 /*
@@ -423,48 +423,6 @@ struct sysfs_device *sysfs_open_bus_device(unsigned char *busname,
 	return rdev;
 }
 
-/**
- * sysfs_find_device_bus: locates the bus a device is on.
- * @dev_id: device id.
- * @busname: buffer to copy name to
- * @bsize: buffer size
- * returns 0 with success or -1 with error
- */
-int sysfs_find_device_bus(const unsigned char *dev_id, unsigned char *busname, 
-								size_t bsize)
-{
-	unsigned char subsys[SYSFS_NAME_LEN], *bus = NULL, *curdev = NULL; 
-	struct dlist *buslist = NULL, *device_list = NULL;
-
-	if (dev_id == NULL || busname == NULL) {
-		errno = EINVAL;
-		return -1;
-	}
-	
-	strcpy(subsys, SYSFS_BUS_DIR);	/* subsys = /bus */
-	buslist = sysfs_open_subsystem_list(subsys);
-	if (buslist != NULL) {
-		dlist_for_each_data(buslist, bus, char) {
-			device_list = sysfs_open_bus_devices_list(bus);
-			if (device_list != NULL) {
-				dlist_for_each_data(device_list, 
-						curdev, char) {
-					if (strcmp(dev_id, curdev) == 0) {
-						strncpy(busname, 
-							bus, bsize);
-						sysfs_close_list(device_list);
-						sysfs_close_list(buslist);
-						return 0;
-					}
-				}
-			sysfs_close_list(device_list);
-			}
-		}
-		sysfs_close_list(buslist);
-	}
-	return -1;
-}
-
 /**
  * sysfs_find_driver_bus: locates the bus the driver is on.
  * @driver: name of the driver to locate
diff --git a/libsysfs/sysfs_class.c b/libsysfs/sysfs_class.c
index cb6ca9d0..a0273565 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);
 }
@@ -116,9 +116,17 @@ static struct sysfs_directory *open_class_dir(const unsigned char *name)
 		return NULL;
 	}
 
-	strcat(classpath, SYSFS_CLASS_DIR);
-	strcat(classpath, "/");
-	strcat(classpath, name);
+	/* 
+	 * 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) {
+		strcat(classpath, SYSFS_BLOCK_DIR);
+	} else {
+		strcat(classpath, SYSFS_CLASS_DIR);
+		strcat(classpath, "/");
+		strcat(classpath, name);
+	}
 	classdir = sysfs_open_directory(classpath);
 	if (classdir == NULL) {
 		errno = EINVAL;
@@ -134,6 +142,39 @@ static struct sysfs_directory *open_class_dir(const unsigned char *name)
 	return classdir;
 }
 
+/** 
+ * set_classdev_classname: Grabs classname from path
+ * @cdev: class device to set
+ * Returns nothing
+ */
+static void set_classdev_classname(struct sysfs_class_device *cdev)
+{
+	unsigned char *c = NULL, *e = NULL;
+	int count = 0;
+
+	c = strstr(cdev->path, SYSFS_CLASS_DIR);
+	if (c == NULL) 
+		c = strstr(cdev->path, SYSFS_BLOCK_DIR);
+	else {
+		c++;
+		while (c != NULL && *c != '/') 
+			c++;
+	}
+
+	if (c == NULL) 
+		strcpy(cdev->classname, SYSFS_UNKNOWN);
+
+	else {
+		c++;
+		e = c;
+		while (e != NULL && *e != '/' && *e != '\0') {
+			e++;
+			count++;
+		}
+		strncpy(cdev->classname, c, count);
+	}
+}
+
 /**
  * sysfs_open_class_device: Opens and populates class device
  * @path: path to class device.
@@ -178,6 +219,7 @@ struct sysfs_class_device *sysfs_open_class_device(const unsigned char *path)
 	sysfs_read_all_subdirs(dir);
 	cdev->directory = dir;
 	strcpy(cdev->path, dir->path);
+	set_classdev_classname(cdev);
 
 	/* get driver and device, if implemented */
 	if (cdev->directory->links != NULL) {
@@ -303,47 +345,73 @@ struct sysfs_class_device *sysfs_get_class_device(struct sysfs_class *class,
 			name, class_name_equal);
 }
 
+/**
+ * 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 unsigned char *classname, 
+		const unsigned char *clsdev, unsigned 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 (strcmp(classname, SYSFS_BLOCK_NAME) == 0) {
+		strcat(path, SYSFS_BLOCK_DIR);
+	} else {
+		strcat(path, SYSFS_CLASS_DIR);
+		strcat(path, "/");
+		strcat(path, classname);
+	}
+	strcat(path, "/");
+	strcat(path, clsdev);
+	return 0;
+}
+
 /**
  * sysfs_open_class_device_by_name: 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)
+		(const unsigned char *classname, const unsigned char *name)
 {
-	struct sysfs_class *class = NULL;
-	struct sysfs_class_device *cdev = NULL, *rcdev = NULL;
+	unsigned 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(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;
 }
 
 /**
@@ -360,53 +428,6 @@ struct dlist *sysfs_get_classdev_attributes(struct sysfs_class_device *cdev)
 	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
- */
-int sysfs_find_device_class(const unsigned char *bus_id, 
-				unsigned char *classname, size_t bsize)
-{
-	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) {
-		errno = EINVAL;
-		return -1;
-	}
-
-	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);
-	}
-	return -1;
-}
-
 /**
  * sysfs_get_classdev_attr: searches class device's attributes by name
  * @clsdev: class device to look through
@@ -433,99 +454,45 @@ struct sysfs_attribute *sysfs_get_classdev_attr
 }
 
 /**
- * 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;
-	}
-	sysfs_close_class_device(clsdev);
-	return 0;
-}
-
-/**
- * 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 unsigned char *classname,
+		const unsigned char *dev, const unsigned char *attrib)
 {
-	struct sysfs_class_device *clsdev = NULL;
 	struct sysfs_attribute *attribute = NULL;
-	unsigned char class_name[SYSFS_NAME_LEN];
+	unsigned 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);
+	strcat(path, "/");
+	strcat(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;
 }
diff --git a/libsysfs/sysfs_device.c b/libsysfs/sysfs_device.c
index 89704dcd..fbd046f2 100644
--- a/libsysfs/sysfs_device.c
+++ b/libsysfs/sysfs_device.c
@@ -23,6 +23,77 @@
 #include "libsysfs.h"
 #include "sysfs.h"
 
+static int confirm_device_bus(struct sysfs_device *dev, 
+				unsigned char *busname, unsigned char *bus_id)
+{
+        struct sysfs_link *devlink = NULL;
+        unsigned char devpath[SYSFS_PATH_MAX];
+	int result = 0;
+
+        if (busname == NULL || bus_id == NULL)
+                return -1;
+
+        if (sysfs_get_mnt_path(devpath, SYSFS_PATH_MAX) != 0)
+                return -1;
+
+        strcat(devpath, SYSFS_BUS_DIR);
+        strcat(devpath, "/");
+        strcat(devpath, busname);
+        strcat(devpath, SYSFS_DEVICES_DIR);
+        strcat(devpath, "/");
+        strcat(devpath, bus_id);
+
+	devlink = sysfs_open_link(devpath);
+	if (devlink == NULL)
+		return -1;
+
+	if (strcmp(devlink->target, dev->path) == 0)
+		result++;
+	sysfs_close_link(devlink);
+	return result;
+}
+
+/**
+ * get_device_bus: retrieves the bus name the device is on, checks path to
+ *	bus' link to make sure it has correct device.
+ * @dev: device to get busname.
+ * returns 0 with success and -1 with error.
+ */
+static int get_device_bus(struct sysfs_device *dev)
+{
+	unsigned char subsys[SYSFS_NAME_LEN], *bus = NULL, *curdev = NULL;
+	struct dlist *buslist = NULL, *device_list = NULL;
+
+	if (dev == NULL) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	strcpy(subsys, SYSFS_BUS_DIR);  /* subsys = /bus */
+	buslist = sysfs_open_subsystem_list(subsys);
+	if (buslist != NULL) {
+		dlist_for_each_data(buslist, bus, char) {
+			device_list = sysfs_open_bus_devices_list(bus);
+			if (device_list != NULL) {
+				dlist_for_each_data(device_list,
+							curdev, char) {
+					if (strcmp(dev->bus_id, curdev) == 0
+					    && confirm_device_bus(dev, bus,
+					    curdev) > 0) {
+						strcpy(dev->bus, bus);
+                                                sysfs_close_list(device_list);
+                                                sysfs_close_list(buslist);
+                                                return 0;
+                                        }
+                                }
+                        sysfs_close_list(device_list);
+                        }
+                }
+                sysfs_close_list(buslist);
+        }
+        return -1;
+}
+
 /**
  * sysfs_close_device_tree: closes every device in the supplied tree, 
  * 	closing children only.
@@ -150,6 +221,9 @@ struct sysfs_device *sysfs_open_device(const unsigned char *path)
 	 * implies that the dev->name and dev->bus_id contain same data.
 	 */
 	strncpy(dev->name, sdir->name, SYSFS_NAME_LEN);
+	
+	if (get_device_bus(dev) != 0)
+		strcpy(dev->bus, SYSFS_UNKNOWN);
 
 	return dev;
 }
@@ -338,55 +412,6 @@ struct dlist *sysfs_get_device_attributes(struct sysfs_device *device)
 	return (device->directory->attributes);
 }
 
-/**
- * sysfs_open_device_by_id: open a device by id (use the "bus" subsystem)
- * @bus_id: bus_id of the device to open - has to be the "bus_id" in 
- * 		/sys/bus/xxx/devices
- * @bus: bus the device belongs to
- * @bsize: size of the bus buffer
- * returns struct sysfs_device if found, NULL otherwise
- * NOTE: 
- * 1. Use sysfs_close_device to close the device
- * 2. Bus the device is on must be supplied
- * 	Use sysfs_find_device_bus to get the bus name
- */
-struct sysfs_device *sysfs_open_device_by_id(const unsigned char *bus_id, 
-		const unsigned char *bus, size_t bsize)
-{
-	char sysfs_path[SYSFS_PATH_MAX], device_path[SYSFS_PATH_MAX];
-	struct sysfs_device *device = NULL;
-
-	if (bus_id == NULL || bus == NULL) {
-		errno = EINVAL;
-		return NULL;
-	}
-	memset(sysfs_path, 0, SYSFS_PATH_MAX);
-	if ((sysfs_get_mnt_path(sysfs_path, SYSFS_PATH_MAX)) != 0) {
-		dprintf("Error getting sysfs mount path\n");
-		return NULL;
-	}
-	strcat(sysfs_path, SYSFS_BUS_DIR);
-	strcat(sysfs_path, "/");
-	strncat(sysfs_path, bus, bsize);
-	strcat(sysfs_path, SYSFS_DEVICES_DIR);
-	strcat(sysfs_path, "/");
-	strcat(sysfs_path, bus_id);
-
-	/* devices under /sys/bus/xxx/devices are links to devices subsystem */
-	if ((sysfs_get_link(sysfs_path, device_path, SYSFS_PATH_MAX)) < 0) {
-		dprintf("Error getting device path\n");
-		return NULL;
-	}
-	
-	device = sysfs_open_device(device_path);
-	if (device == NULL) {
-		dprintf("Error opening device %s\n", bus_id);
-		return NULL;
-	}
-
-	return device;
-}
-
 /**
  * get_device_absolute_path: looks up the bus the device is on, gets 
  * 		absolute path to the device
@@ -395,29 +420,24 @@ struct sysfs_device *sysfs_open_device_by_id(const unsigned char *bus_id,
  * @psize: size of "path"
  * Returns 0 on success -1 on failure
  */
-static int get_device_absolute_path(const unsigned char *device, 
-					unsigned char *path, size_t psize)
+static int get_device_absolute_path(const unsigned char *device,
+		const unsigned char *bus, unsigned char *path, size_t psize)
 {
-	unsigned char bus_name[SYSFS_NAME_LEN], bus_path[SYSFS_PATH_MAX];
+	unsigned char bus_path[SYSFS_NAME_LEN];
 
 	if (device == NULL || path == NULL) {
 		errno = EINVAL;
 		return -1;
 	}
 
-	memset(bus_name, 0, SYSFS_NAME_LEN);
 	memset(bus_path, 0, SYSFS_NAME_LEN);
-	if ((sysfs_find_device_bus(device, bus_name, SYSFS_NAME_LEN)) != 0) {
-		dprintf("Device %s not found\n", device);
-		return -1;
-	}
 	if (sysfs_get_mnt_path(bus_path, SYSFS_PATH_MAX) != 0) {
 		dprintf ("Sysfs not supported on this system\n");
 		return -1;
 	}
 	strcat(bus_path, SYSFS_BUS_DIR);
 	strcat(bus_path, "/");
-	strcat(bus_path, bus_name);
+	strcat(bus_path, bus);
 	strcat(bus_path, SYSFS_DEVICES_DIR);
 	strcat(bus_path, "/");
 	strcat(bus_path, device);
@@ -433,106 +453,85 @@ static int get_device_absolute_path(const unsigned char *device,
 }
 
 /**
- * sysfs_write_device_attr: modify a "writable" attribute for the given device
- * @dev: device bus_id for which attribute has to be changed
- * @attrib: attribute to change
- * @value: value to change to
- * @len: "value" length to write
- * Returns 0 on success -1 on error
- */ 
-int sysfs_write_device_attr(unsigned char *dev, unsigned char *attrib,
-					unsigned char *value, size_t len)
+ * sysfs_open_device_by_id: open a device by id (use the "bus" subsystem)
+ * @bus_id: bus_id of the device to open - has to be the "bus_id" in 
+ * 		/sys/bus/xxx/devices
+ * @bus: bus the device belongs to
+ * @bsize: size of the bus buffer
+ * returns struct sysfs_device if found, NULL otherwise
+ * NOTE: 
+ * 1. Use sysfs_close_device to close the device
+ * 2. Bus the device is on must be supplied
+ * 	Use sysfs_find_device_bus to get the bus name
+ */
+struct sysfs_device *sysfs_open_device_by_id(const unsigned char *bus_id, 
+		const unsigned char *bus, size_t bsize)
 {
-	struct sysfs_attribute *attribute = NULL;
-	unsigned char devpath[SYSFS_PATH_MAX];
+	char sysfs_path[SYSFS_PATH_MAX];
+	struct sysfs_device *device = NULL;
 
-	if (dev == NULL || attrib == NULL || value == NULL) {
+	if (bus_id == NULL || bus == NULL) {
 		errno = EINVAL;
-		return -1;
-	}
-	
-	memset(devpath, 0, SYSFS_PATH_MAX);
-	if ((get_device_absolute_path(dev, devpath, SYSFS_PATH_MAX)) != 0) {
-		dprintf("Error finding absolute path to device %s\n", dev);
-		return -1;
-	}
-	strcat(devpath, "/");
-	strcat(devpath, attrib);
-	attribute = sysfs_open_attribute(devpath);
-	if (attribute == NULL) {
-		dprintf("Attribute %s could not be retrieved for device %s\n",
-				attrib, dev);
-		return -1;
+		return NULL;
 	}
-	if (attribute->method & SYSFS_METHOD_SHOW) {
-		if ((sysfs_read_attribute(attribute)) != 0) {
-			dprintf("Error reading attribute %s for device %s\n",
-					attrib, dev);
-			sysfs_close_attribute(attribute);
-			return -1;
-		}
+	memset(sysfs_path, 0, SYSFS_PATH_MAX);
+	if ((get_device_absolute_path(bus_id, bus, sysfs_path, 
+						SYSFS_PATH_MAX)) != 0) {
+		dprintf("Error getting to device %s\n", bus_id);
+		return NULL;
 	}
-	if ((sysfs_write_attribute(attribute, value, len)) < 0) {
-		dprintf("Error setting %s to %s\n", attrib, value);
-		sysfs_close_attribute(attribute);
-		return -1;
+	
+	device = sysfs_open_device(sysfs_path);
+	if (device == NULL) {
+		dprintf("Error opening device %s\n", bus_id);
+		return NULL;
 	}
-	sysfs_close_attribute(attribute);
-	return 0;
+
+	return device;
 }
 
-/**
- * sysfs_read_device_attr: read an attribute of the given device
- * @dev: device bus_id for which attribute has to be changed
- * @attrib: attribute to read
- * @value: buffer to return value in
- * @len: size of buffer available
- * Returns 0 on success -1 on error
- */ 
-int sysfs_read_device_attr(unsigned char *dev, unsigned char *attrib,
-					unsigned char *value, size_t len)
+/*
+ * sysfs_open_device_attr: open the given device's attribute
+ * @bus: Bus on which to look
+ * @dev_id: device for which attribute is required
+ * @attrname: name of the attribute to look for
+ * Returns struct sysfs_attribute on success and NULL on failure
+ * 
+ * NOTE:
+ * 	A call to sysfs_close_attribute() is required to close
+ * 	the attribute returned and free memory. 
+ */
+struct sysfs_attribute *sysfs_open_device_attr(const unsigned char *bus,
+		const unsigned char *bus_id, const unsigned char *attrib)
 {
 	struct sysfs_attribute *attribute = NULL;
 	unsigned char devpath[SYSFS_PATH_MAX];
-
-	if (dev == NULL || attrib == NULL || value == NULL) {
+	
+	if (bus == NULL || bus_id == NULL || attrib == NULL) {
 		errno = EINVAL;
-		return -1;
+		return NULL;
 	}
-	
+
 	memset(devpath, 0, SYSFS_PATH_MAX);
-	if ((get_device_absolute_path(dev, devpath, SYSFS_PATH_MAX)) != 0) {
-		dprintf("Error finding absolute path to device %s\n", dev);
-		return -1;
+	if ((get_device_absolute_path(bus_id, bus, devpath, 
+					SYSFS_PATH_MAX)) != 0) {
+		dprintf("Error getting to device %s\n", bus_id);
+		return NULL;
 	}
 	strcat(devpath, "/");
 	strcat(devpath, attrib);
 	attribute = sysfs_open_attribute(devpath);
 	if (attribute == NULL) {
 		dprintf("Error opening attribute %s for device %s\n",
-				attrib, dev);
-		return -1;
-	}
-	if (!(attribute->method & SYSFS_METHOD_SHOW)) {
-		dprintf("Show method not supported for attribute %s\n",
-				attrib);
-		sysfs_close_attribute(attribute);
-		return -1;
+				attrib, bus_id);
+		return NULL;
 	}
 	if ((sysfs_read_attribute(attribute)) != 0) {
 		dprintf("Error reading attribute %s for device %s\n",
-				attrib, dev);
+				attrib, bus_id);
 		sysfs_close_attribute(attribute);
-		return -1;
-	}
-	if (attribute->len > len) {
-		dprintf("Value length %d is larger than supplied buffer %d\n",
-				attribute->len, len);
-		sysfs_close_attribute(attribute);
-		return -1;
+		return NULL;
 	}
-	strncpy(value, attribute->value, attribute->len);
-	value[(attribute->len)+1] = 0;
-	sysfs_close_attribute(attribute);
-	return 0;
+	return attribute;
 }
+
diff --git a/libsysfs/sysfs_driver.c b/libsysfs/sysfs_driver.c
index f8e842c6..0011177e 100644
--- a/libsysfs/sysfs_driver.c
+++ b/libsysfs/sysfs_driver.c
@@ -162,6 +162,35 @@ struct dlist *sysfs_get_driver_links(struct sysfs_driver *driver)
 	return(driver->directory->links);
 }
 
+/**
+ * get_driver_path: looks up the bus the driver is on and builds path to
+ * 		the driver.
+ * @bus: bus on which to search
+ * @drv: driver to look for
+ * @path: buffer to return path to driver
+ * @psize: size of "path"
+ * Returns 0 on success and -1 on error
+ */
+static int get_driver_path(const unsigned char *bus, const unsigned char *drv, 
+				unsigned char *path, size_t psize)
+{
+	if (bus == NULL || drv == NULL || path == NULL) {
+		errno = EINVAL;
+		return -1;
+	}
+	if (sysfs_get_mnt_path(path, psize) != 0) {
+		dprintf("Error getting sysfs mount path\n");
+		return -1;
+	}
+	strcat(path, SYSFS_BUS_DIR);
+	strcat(path, "/");
+	strcat(path, bus);
+	strcat(path, SYSFS_DRIVERS_DIR);
+	strcat(path, "/");
+	strcat(path, drv);
+	return 0;
+}
+
 /**
  * sysfs_open_driver_by_name: open a driver by name and return the bus
  * the driver is on.
@@ -188,16 +217,10 @@ struct sysfs_driver *sysfs_open_driver_by_name(const unsigned char *drv_name,
 	}
 
 	memset(path, 0, SYSFS_PATH_MAX);
-	if (sysfs_get_mnt_path(path, SYSFS_PATH_MAX) != 0) {
-		dprintf("Error getting sysfs mount path\n");
+	if (get_driver_path(bus, drv_name, path, SYSFS_PATH_MAX) != 0) {
+		dprintf("Error getting to driver %s\n", drv_name);
 		return NULL;
 	}
-	strcat(path, SYSFS_BUS_DIR);
-	strcat(path, "/");
-	strcat(path, bus);
-	strcat(path, SYSFS_DRIVERS_DIR);
-	strcat(path, "/");
-	strcat(path, drv_name);
 	driver = sysfs_open_driver(path);
 	if (driver == NULL) {
 		dprintf("Could not open driver %s\n", drv_name);
@@ -224,114 +247,33 @@ struct sysfs_driver *sysfs_open_driver_by_name(const unsigned char *drv_name,
 	return driver;
 }
 
-/**
- * get_driver_path: looks up the bus the driver is on and builds path to
- * 		the driver.
- * @drv: driver to look for
- * @path: buffer to return path to driver
- * @psize: size of "path"
- * Returns 0 on success and -1 on error
- */
-static int get_driver_path(const unsigned char *drv, 
-				unsigned char *path, size_t psize)
-{
-	unsigned char bus_name[SYSFS_NAME_LEN];
-
-	if (drv == NULL || path == NULL) {
-		errno = EINVAL;
-		return -1;
-	}
-	memset(bus_name, 0, SYSFS_NAME_LEN);
-	memset(path, 0, SYSFS_PATH_MAX);
-	if ((sysfs_find_driver_bus(drv, bus_name, SYSFS_NAME_LEN)) < 0) {
-		dprintf("Driver %s not found\n", drv);
-		return -1;
-	}
-	if (sysfs_get_mnt_path(path, SYSFS_PATH_MAX) != 0) {
-		dprintf("Error getting sysfs mount path\n");
-		return -1;
-	}
-	strcat(path, SYSFS_BUS_DIR);
-	strcat(path, "/");
-	strcat(path, bus_name);
-	strcat(path, SYSFS_DRIVERS_DIR);
-	strcat(path, "/");
-	strcat(path, drv);
-	fprintf(stdout, "get_driver_path %s\n", path);
-	return 0;
-}
-
-/**
- * sysfs_write_driver_attr: modify "writable" driver attribute
- * @drv: driver whose attribute has to be modified
- * @attrib: Attribute to be modified
- * @value: Value to change to
- * Returns 0 on success -1 on failure
- */ 
-int sysfs_write_driver_attr(unsigned char *drv, unsigned char *attrib,
-					unsigned char *value, size_t len)
-{
-	struct sysfs_attribute *attribute = NULL;
-	unsigned char path[SYSFS_PATH_MAX];
-
-	if (drv == NULL || attrib == NULL || value == NULL) {
-		errno = EINVAL;
-		return -1;
-	}
-
-	memset(path, 0, SYSFS_PATH_MAX);
-	if ((get_driver_path(drv, path, SYSFS_PATH_MAX)) != 0) {
-		dprintf("Error getting to driver %s\n", drv);
-		return -1;
-	}
-	strcat(path, "/");
-	strcat(path, attrib);
-	attribute = sysfs_open_attribute(path);
-        if (attribute == NULL) {
-                dprintf("Attribute %s could not be retrieved for driver %s\n",
-							attrib, drv);
-		return -1;
-	}
-	if (attribute->method & SYSFS_METHOD_SHOW) {
-		if ((sysfs_read_attribute(attribute)) != 0) {
-			dprintf("Error reading attribute %s for driver %s\n",
-					attrib, drv);
-			sysfs_close_attribute(attribute);
-			return -1;
-		}
-	}
-	if ((sysfs_write_attribute(attribute, value, len)) < 0) {
-		dprintf("Error setting %s to %s\n", attrib, value);
-		sysfs_close_attribute(attribute);
-		return -1;
-	}
-	sysfs_close_attribute(attribute);
-	return 0;
-}
 
 /**
- * sysfs_read_driver_attr: read the user supplied driver attribute
+ * sysfs_open_driver_attr: read the user supplied driver attribute
+ * @bus: bus on which to look 
  * @drv: driver whose attribute has to be read
  * @attrib: Attribute to be read
- * @value: Buffer to return the read value
- * @len: Length of the buffer "value"
- * Returns 0 on success -1 on failure
+ * Returns struct sysfs_attribute on success and NULL on failure
+ *
+ * NOTE:
+ * 	A call to sysfs_close_attribute() is required to close the
+ * 	attribute returned and to free memory
  */ 
-int sysfs_read_driver_attr(unsigned char *drv, unsigned char *attrib,
-					unsigned char *value, size_t len)
+struct sysfs_attribute *sysfs_open_driver_attr(const unsigned char *bus, 
+		const unsigned char *drv, const unsigned char *attrib)
 {
 	struct sysfs_attribute *attribute = NULL;
 	unsigned char path[SYSFS_PATH_MAX];
 
-	if (drv == NULL || attrib == NULL || value == NULL) {
+	if (bus == NULL || drv == NULL || attrib == NULL) {
 		errno = EINVAL;
-		return -1;
+		return NULL;
 	}
 
 	memset(path, 0, SYSFS_NAME_LEN);
-	if ((get_driver_path(drv, path, SYSFS_PATH_MAX)) != 0) {
+	if ((get_driver_path(bus, drv, path, SYSFS_PATH_MAX)) != 0) {
 		dprintf("Error getting to driver %s\n", drv);
-		return -1;
+		return NULL;
 	}
 	strcat(path, "/");
 	strcat(path, attrib);
@@ -339,29 +281,14 @@ int sysfs_read_driver_attr(unsigned char *drv, unsigned char *attrib,
         if (attribute == NULL) {
 		dprintf("Error opening attribute %s for driver %s\n",
 				attrib, drv);
-		return -1;
-	}
-	if (!(attribute->method & SYSFS_METHOD_SHOW)) {
-		dprintf("Show method not supported for attribute %s\n",
-				attrib);
-		sysfs_close_attribute(attribute);
-		return -1;
+		return NULL;
 	}
 	if ((sysfs_read_attribute(attribute)) != 0) {
                 dprintf("Error reading attribute %s for driver %s\n", 
 				attrib, drv);
 		sysfs_close_attribute(attribute);
-		return -1;
-	}
-	if (attribute->len > len) {
-		dprintf("Value length %d is larger than supplied buffer %d\n",
-				attribute->len, len);
-		sysfs_close_attribute(attribute);
-		return -1;
+		return NULL;
 	}
-	strncpy(value, attribute->value, attribute->len);
-	value[(attribute->len)+1] = 0;
-	sysfs_close_attribute(attribute);
-	return 0;
+	return attribute;
 }
 
diff --git a/libsysfs/sysfs_utils.c b/libsysfs/sysfs_utils.c
index 3e50bc61..4e96051c 100644
--- a/libsysfs/sysfs_utils.c
+++ b/libsysfs/sysfs_utils.c
@@ -92,7 +92,7 @@ int sysfs_get_mnt_path(unsigned char *mnt_path, size_t len)
 		return -1;
 	}
 	sysfs_path = getenv(SYSFS_PATH_ENV);
-	if (sysfs_path != NULL)
+	if (sysfs_path != NULL) 
 		strncpy(mnt_path, sysfs_path, len);
 	else
 		ret = sysfs_get_fs_mnt_path(SYSFS_FSTYPE_NAME, mnt_path, len);
@@ -109,13 +109,19 @@ int sysfs_get_mnt_path(unsigned char *mnt_path, size_t len)
 int sysfs_get_name_from_path(const unsigned char *path, unsigned char *name, 
 								size_t len)
 {
+	unsigned char tmp[SYSFS_PATH_MAX];
 	unsigned char *n = NULL;
                                                                                 
 	if (path == NULL || name == NULL) {
 		errno = EINVAL;
 		return -1;
 	}
-	n = strrchr(path, '/');
+	memset(tmp, 0, SYSFS_PATH_MAX);
+	strcpy(tmp, path);
+	n = &tmp[strlen(tmp)-1];
+	if (strncmp(n, "/", 1) == 0)
+		*n = '\0';	
+	n = strrchr(tmp, '/');
 	if (n == NULL) {
 		errno = EINVAL;
 		return -1;
@@ -169,10 +175,7 @@ int sysfs_get_link(const unsigned char *path, unsigned char *target, size_t len)
 		if (*s == '/')
 			count++;
 	}
-
-	if (s == NULL)
-		return -1;
-
+	
 	strncpy(s, d, (SYSFS_PATH_MAX-strlen(devdir)));
 	strncpy(target, devdir, len);
 
@@ -184,7 +187,7 @@ int sysfs_get_link(const unsigned char *path, unsigned char *target, size_t len)
  * sysfs_del_name: free function for sysfs_open_subsystem_list
  * @name: memory area to be freed
  */ 
-void sysfs_del_name(void *name)
+static void sysfs_del_name(void *name)
 {
 	free(name);
 }
@@ -210,8 +213,10 @@ void sysfs_close_list(struct dlist *list)
 struct dlist *sysfs_open_subsystem_list(unsigned char *name)
 {
 	unsigned char sysfs_path[SYSFS_PATH_MAX], *subsys_name = NULL;
+	unsigned char *c = NULL;
 	struct sysfs_directory *dir = NULL, *cur = NULL;
 	struct dlist *list = NULL;
+	struct stat astats;
 	
 	if (name == NULL)
 		return NULL;
@@ -251,6 +256,27 @@ struct dlist *sysfs_open_subsystem_list(unsigned char *name)
 		}
 	}
 	sysfs_close_directory(dir);
+	/*
+	 * We are now considering "block" as a "class". Hence, if the subsys
+	 * name requested here is "class", verify if "block" is supported on
+	 * this system and return the same.
+	 */ 
+	if (strcmp(name, SYSFS_CLASS_DIR) == 0) {
+		c = strstr(sysfs_path, SYSFS_CLASS_NAME);
+		if (c == NULL)
+			goto out;
+		strcpy(c, SYSFS_BLOCK_NAME);
+		if ((lstat(sysfs_path, &astats)) != 0) {
+			dprintf("stat() failed\n");
+			goto out;
+		}
+		if (S_ISDIR(astats.st_mode)) {
+			subsys_name = (char *)calloc(1, SYSFS_NAME_LEN);
+			strcpy(subsys_name, SYSFS_BLOCK_NAME);
+			dlist_unshift(list, subsys_name);
+		}
+	}
+out:
 	return list;
 }