[PATCH] udev - drop all methods :)

[elogind.git] / libsysfs / sysfs_device.c

diff --git a/libsysfs/sysfs_device.c b/libsysfs/sysfs_device.c
index 89704dcd8041092abf6b9f8e6c6362a1bf43ba84..66d5f9aef7c71b65b9e9272b053eb4bac8a21525 100644 (file)
--- a/libsysfs/sysfs_device.c
+++ b/libsysfs/sysfs_device.c
@@ -23,6 +23,67 @@
 #include "libsysfs.h"
 #include "sysfs.h"
 
 #include "libsysfs.h"
 #include "sysfs.h"
 

+/**
+ * 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], path[SYSFS_PATH_MAX];
+       unsigned char target[SYSFS_PATH_MAX], *bus = NULL, *c = NULL;
+       struct dlist *buslist = NULL;
+
+       if (dev == NULL) {
+               errno = EINVAL;
+               return -1;
+       }
+
+       memset(subsys, 0, SYSFS_NAME_LEN);
+       strcat(subsys, "/");
+       strcpy(subsys, SYSFS_BUS_NAME);  /* subsys = /bus */
+       buslist = sysfs_open_subsystem_list(subsys);
+       if (buslist != NULL) {
+               dlist_for_each_data(buslist, bus, char) {
+                       memset(path, 0, SYSFS_PATH_MAX);
+                       strcpy(path, dev->path);
+                       c = strstr(path, "/devices");
+                       if (c == NULL) {
+                               dprintf("Invalid path to device %s\n", path);
+                               sysfs_close_list(buslist);
+                               return -1;
+                       }
+                       *c = '\0';
+                       strcat(path, "/");
+                       strcat(path, SYSFS_BUS_NAME);
+                       strcat(path, "/");
+                       strcat(path, bus);
+                       strcat(path, "/");
+                       strcat(path, SYSFS_DEVICES_NAME);
+                       strcat(path, "/");
+                       strcat(path, dev->bus_id);
+                       if ((sysfs_path_is_link(path)) == 0) {
+                               memset(target, 0, SYSFS_PATH_MAX);
+                               if ((sysfs_get_link(path, target, 
+                                                       SYSFS_PATH_MAX)) != 0) {
+                                       dprintf("Error getting link target\n");
+                                       sysfs_close_list(buslist);
+                                       return -1;
+                               }
+                               if (!(strncmp(target, dev->path, 
+                                                       SYSFS_PATH_MAX))) {
+                                       strcpy(dev->bus, bus);
+                                       sysfs_close_list(buslist);
+                                       return 0;
+                               }
+                       }
+                }
+                sysfs_close_list(buslist);
+        }
+        return -1;
+}
+

 /**
  * sysfs_close_device_tree: closes every device in the supplied tree, 
  *     closing children only.
 /**
  * sysfs_close_device_tree: closes every device in the supplied tree, 
  *     closing children only.


@@ -43,14 +104,6 @@ static void sysfs_close_device_tree(struct sysfs_device *devroot)
        }
 }
 
        }
 }
 

-/**
- * sysfs_del_device: routine for dlist integration
- */
-static void sysfs_del_device(void *dev)
-{
-       sysfs_close_device((struct sysfs_device *)dev);
-}
-

 /**
  * sysfs_close_dev_tree: routine for dlist integration
  */
 /**
  * sysfs_close_dev_tree: routine for dlist integration
  */


@@ -66,6 +119,8 @@ static void sysfs_close_dev_tree(void *dev)
 void sysfs_close_device(struct sysfs_device *dev)
 {
        if (dev != NULL) {
 void sysfs_close_device(struct sysfs_device *dev)
 {
        if (dev != NULL) {

+               if (dev->parent != NULL)
+                       sysfs_close_device(dev->parent);

                if (dev->directory != NULL)
                        sysfs_close_directory(dev->directory);
                if (dev->children != NULL && dev->children->count == 0)
                if (dev->directory != NULL)
                        sysfs_close_directory(dev->directory);
                if (dev->children != NULL && dev->children->count == 0)


@@ -84,72 +139,73 @@ static struct sysfs_device *alloc_device(void)
 }
 
 /**
 }
 
 /**

- * sysfs_get_device_attr: searches dev's attributes by name
- * @dev: device to look through
- * @name: attribute name to get
- * returns sysfs_attribute reference with success or NULL with error.
+ * open_device_dir: opens up sysfs_directory for specific root dev
+ * @name: name of root
+ * returns struct sysfs_directory with success and NULL with error

  */
  */

-struct sysfs_attribute *sysfs_get_device_attr(struct sysfs_device *dev,
-                                               const unsigned char *name)
+static struct sysfs_directory *open_device_dir(const unsigned char *path)

 {
 {

-       struct sysfs_attribute *cur = NULL;
+       struct sysfs_directory *rdir = NULL;

 
 

-       if (dev == NULL || dev->directory == NULL 
-           || dev->directory->attributes == NULL || name == NULL) {
+       if (path == NULL) {

                errno = EINVAL;
                return NULL;
        }
                errno = EINVAL;
                return NULL;
        }

-       
-       cur = sysfs_get_directory_attribute(dev->directory, 
-                       (unsigned char *)name);
-       if (cur != NULL)
-               return cur;

 
 

-       return NULL;
+       rdir = sysfs_open_directory(path);
+       if (rdir == NULL) {
+               errno = EINVAL;
+               dprintf ("Device %s not supported on this system\n", path);
+               return NULL;
+       }
+       if ((sysfs_read_dir_subdirs(rdir)) != 0) {
+               dprintf ("Error reading device at dir %s\n", path);
+               sysfs_close_directory(rdir);
+               return NULL;
+       }
+       
+       return rdir;

 }
 
 /**
 }
 
 /**

- * sysfs_open_device: opens and populates device structure
+ * sysfs_open_device_path: opens and populates device structure

  * @path: path to device, this is the /sys/devices/ path
  * returns sysfs_device structure with success or NULL with error
  */
  * @path: path to device, this is the /sys/devices/ path
  * returns sysfs_device structure with success or NULL with error
  */

-struct sysfs_device *sysfs_open_device(const unsigned char *path)
+struct sysfs_device *sysfs_open_device_path(const unsigned char *path)

 {
        struct sysfs_device *dev = NULL;
 {
        struct sysfs_device *dev = NULL;

-       struct sysfs_directory *sdir = NULL;

 
        if (path == NULL) {
                errno = EINVAL;
                return NULL;
        }
 
        if (path == NULL) {
                errno = EINVAL;
                return NULL;
        }

+       if ((sysfs_path_is_dir(path)) != 0) {
+               dprintf("Incorrect path to device: %s\n", path);
+               return NULL;
+       }

        dev = alloc_device();   
        if (dev == NULL) {
                dprintf("Error allocating device at %s\n", path);
                return NULL;
        }
        dev = alloc_device();   
        if (dev == NULL) {
                dprintf("Error allocating device at %s\n", path);
                return NULL;
        }

-       sdir = sysfs_open_directory(path);
-       if (sdir == NULL) {
-               dprintf("Invalid device at %s\n", path);
+       if ((sysfs_get_name_from_path(path, dev->bus_id, 
+                                       SYSFS_NAME_LEN)) != 0) {

                errno = EINVAL;
                errno = EINVAL;

+               dprintf("Error getting device bus_id\n");

                sysfs_close_device(dev);
                return NULL;
        }
                sysfs_close_device(dev);
                return NULL;
        }

-       if ((sysfs_read_directory(sdir)) != 0) {
-               dprintf("Error reading device directory at %s\n", path);
-               sysfs_close_directory(sdir);
-               sysfs_close_device(dev);
-               return NULL;
-       }
-       dev->directory = sdir;
-       strcpy(dev->bus_id, sdir->name);
-       strcpy(dev->path, sdir->path);
-
+       strcpy(dev->path, path);

        /* 
         * The "name" attribute no longer exists... return the device's
         * sysfs representation instead, in the "dev->name" field, which
         * implies that the dev->name and dev->bus_id contain same data.
         */
        /* 
         * The "name" attribute no longer exists... return the device's
         * sysfs representation instead, in the "dev->name" field, which
         * implies that the dev->name and dev->bus_id contain same data.
         */

-       strncpy(dev->name, sdir->name, SYSFS_NAME_LEN);
+       strncpy(dev->name, dev->bus_id, SYSFS_NAME_LEN);
+       
+       if (get_device_bus(dev) != 0)
+               strcpy(dev->bus, SYSFS_UNKNOWN);

 
        return dev;
 }
 
        return dev;
 }


@@ -170,11 +226,16 @@ static struct sysfs_device *sysfs_open_device_tree(const unsigned char *path)
                errno = EINVAL;
                return NULL;
        }
                errno = EINVAL;
                return NULL;
        }

-       rootdev = sysfs_open_device(path);
+       rootdev = sysfs_open_device_path(path);

        if (rootdev == NULL) {
                dprintf("Error opening root device at %s\n", path);
                return NULL;
        }
        if (rootdev == NULL) {
                dprintf("Error opening root device at %s\n", path);
                return NULL;
        }

+       if (rootdev->directory == NULL) {
+               rootdev->directory = open_device_dir(rootdev->path);
+               if (rootdev->directory == NULL) 
+                       return NULL;
+       }

        if (rootdev->directory->subdirs != NULL) {
                dlist_for_each_data(rootdev->directory->subdirs, cur,
                                struct sysfs_directory) {
        if (rootdev->directory->subdirs != NULL) {
                dlist_for_each_data(rootdev->directory->subdirs, cur,
                                struct sysfs_directory) {


@@ -188,7 +249,7 @@ static struct sysfs_device *sysfs_open_device_tree(const unsigned char *path)
                        if (rootdev->children == NULL)
                                rootdev->children = dlist_new_with_delete
                                        (sizeof(struct sysfs_device),
                        if (rootdev->children == NULL)
                                rootdev->children = dlist_new_with_delete
                                        (sizeof(struct sysfs_device),

-                                       sysfs_del_device);
+                                       sysfs_close_dev_tree);

                        dlist_unshift(rootdev->children, new);
                }
        }
                        dlist_unshift(rootdev->children, new);
                }
        }


@@ -212,60 +273,25 @@ void sysfs_close_root_device(struct sysfs_root_device *root)
 }
 
 /**
 }
 
 /**

- * open_root_device_dir: opens up sysfs_directory for specific root dev
- * @name: name of root
- * returns struct sysfs_directory with success and NULL with error
- */
-static struct sysfs_directory *open_root_device_dir(const unsigned char *name)
-{
-       struct sysfs_directory *rdir = NULL;
-       unsigned char rootpath[SYSFS_PATH_MAX];
-
-       if (name == NULL) {
-               errno = EINVAL;
-               return NULL;
-       }
-
-       memset(rootpath, 0, SYSFS_PATH_MAX);
-       if (sysfs_get_mnt_path(rootpath, SYSFS_PATH_MAX) != 0) {
-               dprintf ("Sysfs not supported on this system\n");
-               return NULL;
-       }
-
-       strcat(rootpath, SYSFS_DEVICES_DIR);
-       strcat(rootpath, "/");
-       strcat(rootpath, name);
-       rdir = sysfs_open_directory(rootpath);
-       if (rdir == NULL) {
-               errno = EINVAL;
-               dprintf ("Root device %s not supported on this system\n",
-                       name);
-               return NULL;
-       }
-       if (sysfs_read_directory(rdir) != 0) {
-               dprintf ("Error reading %s root device at dir %s\n", name,
-                       rootpath);
-               sysfs_close_directory(rdir);
-               return NULL;
-       }
-       
-       return rdir;
-}
-
-/**
- * get_all_root_devices: opens up all the devices under this root device
+ * sysfs_get_root_devices: opens up all the devices under this root device

  * @root: root device to open devices for
  * @root: root device to open devices for

- * returns 0 with success and -1 with error
+ * returns dlist of devices with success and NULL with error

  */
  */

-static int get_all_root_devices(struct sysfs_root_device *root)
+struct dlist *sysfs_get_root_devices(struct sysfs_root_device *root)

 {
        struct sysfs_device *dev = NULL;
        struct sysfs_directory *cur = NULL;
 
 {
        struct sysfs_device *dev = NULL;
        struct sysfs_directory *cur = NULL;
 

-       if (root == NULL || root->directory == NULL) {
+       if (root == NULL) {

                errno = EINVAL;
                errno = EINVAL;

-               return -1;
+               return NULL;
+       }
+       if (root->directory == NULL) {
+               root->directory = open_device_dir(root->path);
+               if (root->directory == NULL)
+                       return NULL;

        }
        }

+               

        if (root->directory->subdirs == NULL)
                return 0;
 
        if (root->directory->subdirs == NULL)
                return 0;
 


@@ -283,7 +309,7 @@ static int get_all_root_devices(struct sysfs_root_device *root)
                dlist_unshift(root->devices, dev);
        }
 
                dlist_unshift(root->devices, dev);
        }
 

-       return 0;
+       return root->devices;

 }
 
 /**
 }
 
 /**


@@ -295,33 +321,37 @@ static int get_all_root_devices(struct sysfs_root_device *root)
 struct sysfs_root_device *sysfs_open_root_device(const unsigned char *name)
 {
        struct sysfs_root_device *root = NULL;
 struct sysfs_root_device *sysfs_open_root_device(const unsigned char *name)
 {
        struct sysfs_root_device *root = NULL;

-       struct sysfs_directory *rootdir = NULL;
+       unsigned char rootpath[SYSFS_PATH_MAX];

 
        if (name == NULL) {
                errno = EINVAL;
                return NULL;
        }
 
 
        if (name == NULL) {
                errno = EINVAL;
                return NULL;
        }
 

-       root = (struct sysfs_root_device *)calloc
-                                       (1, sizeof(struct sysfs_root_device));
-       if (root == NULL) {
-               dprintf("calloc failure\n");
+       memset(rootpath, 0, SYSFS_PATH_MAX);
+       if (sysfs_get_mnt_path(rootpath, SYSFS_PATH_MAX) != 0) {
+               dprintf ("Sysfs not supported on this system\n");

                return NULL;
        }
                return NULL;
        }

-       rootdir = open_root_device_dir(name);
-       if (rootdir == NULL) {
-               dprintf ("Invalid root device, %s not supported\n", name);
-               sysfs_close_root_device(root);
+
+       if (sysfs_trailing_slash(rootpath) == 0)
+               strcat(rootpath, "/");
+       strcat(rootpath, SYSFS_DEVICES_NAME);
+       strcat(rootpath, "/");
+       strcat(rootpath, name);
+       if ((sysfs_path_is_dir(rootpath)) != 0) {
+               errno = EINVAL;
+               dprintf("Invalid root device: %s\n", name);

                return NULL;
        }
                return NULL;
        }

-       strcpy(root->path, rootdir->path);
-       root->directory = rootdir;
-       if (get_all_root_devices(root) != 0) {
-               dprintf ("Error retrieving devices for root %s\n", name);
-               sysfs_close_root_device(root);
+       root = (struct sysfs_root_device *)calloc
+                                       (1, sizeof(struct sysfs_root_device));
+       if (root == NULL) {
+               dprintf("calloc failure\n");

                return NULL;
        }
                return NULL;
        }

-
+       strcpy(root->name, name);
+       strcpy(root->path, rootpath);

        return root;
 }
 
        return root;
 }
 


@@ -332,59 +362,56 @@ struct sysfs_root_device *sysfs_open_root_device(const unsigned char *name)
  */
 struct dlist *sysfs_get_device_attributes(struct sysfs_device *device)
 {
  */
 struct dlist *sysfs_get_device_attributes(struct sysfs_device *device)
 {

-       if (device == NULL || device->directory == NULL) 
+       if (device == NULL) 

                return NULL;
 
                return NULL;
 

+       if (device->directory == NULL) {
+               device->directory = sysfs_open_directory(device->path);
+               if (device->directory == NULL) 
+                       return NULL;
+       }
+       if (device->directory->attributes == NULL) {
+               if ((sysfs_read_dir_attributes(device->directory)) != 0)
+                       return NULL;
+       } else {
+               if ((sysfs_path_is_dir(device->path)) != 0) {
+                       dprintf("Device at %s no longer exists", device->path);
+                       return NULL;
+               }
+               if ((sysfs_refresh_attributes
+                               (device->directory->attributes)) != 0) {
+                       dprintf("Error refreshing device attributes\n");
+                       return NULL;
+               }
+       }

        return (device->directory->attributes);
 }
 
 /**
        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
+ * sysfs_get_device_attr: searches dev's attributes by name
+ * @dev: device to look through
+ * @name: attribute name to get
+ * returns sysfs_attribute reference with success or NULL with error.

  */
  */

-struct sysfs_device *sysfs_open_device_by_id(const unsigned char *bus_id, 
-               const unsigned char *bus, size_t bsize)
+struct sysfs_attribute *sysfs_get_device_attr(struct sysfs_device *dev,
+                                               const unsigned char *name)

 {
 {

-       char sysfs_path[SYSFS_PATH_MAX], device_path[SYSFS_PATH_MAX];
-       struct sysfs_device *device = NULL;
+       struct sysfs_attribute *cur = NULL;
+       struct dlist *attrlist = NULL;

 
 

-       if (bus_id == NULL || bus == NULL) {
+       if (dev == NULL || name == NULL) {

                errno = EINVAL;
                return 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");
+       attrlist = sysfs_get_device_attributes(dev);
+       if (attrlist == NULL)

                return NULL;
                return NULL;

-       }
-       
-       device = sysfs_open_device(device_path);
-       if (device == NULL) {
-               dprintf("Error opening device %s\n", bus_id);
-               return NULL;
-       }

 
 

-       return device;
+       cur = sysfs_get_directory_attribute(dev->directory, 
+                       (unsigned char *)name);
+
+       return cur;

 }
 
 /**
 }
 
 /**


@@ -395,30 +422,28 @@ struct sysfs_device *sysfs_open_device_by_id(const unsigned char *bus_id,
  * @psize: size of "path"
  * Returns 0 on success -1 on failure
  */
  * @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_PATH_MAX];

 
        if (device == NULL || path == NULL) {
                errno = EINVAL;
                return -1;
        }
 
 
        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;
-       }
+       memset(bus_path, 0, SYSFS_PATH_MAX);

        if (sysfs_get_mnt_path(bus_path, SYSFS_PATH_MAX) != 0) {
                dprintf ("Sysfs not supported on this system\n");
                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);
+       if (sysfs_trailing_slash(bus_path) == 0)
+               strcat(bus_path, "/");
+       strcat(bus_path, SYSFS_BUS_NAME);

        strcat(bus_path, "/");
        strcat(bus_path, "/");

-       strcat(bus_path, bus_name);
-       strcat(bus_path, SYSFS_DEVICES_DIR);
+       strcat(bus_path, bus);
+       strcat(bus_path, "/");
+       strcat(bus_path, SYSFS_DEVICES_NAME);

        strcat(bus_path, "/");
        strcat(bus_path, device);
        /*
        strcat(bus_path, "/");
        strcat(bus_path, device);
        /*


@@ -433,106 +458,138 @@ 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: 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
+ * 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(const unsigned char *bus_id, 
+                                               const unsigned char *bus)

 {
 {

-       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;
                errno = EINVAL;

-               return -1;
+               return NULL;
+       }
+       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;

        }
        
        }
        

-       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;
+       device = sysfs_open_device_path(sysfs_path);
+       if (device == NULL) {
+               dprintf("Error opening device %s\n", bus_id);
+               return NULL;

        }
        }

-       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 device;
+}
+
+/**
+ * sysfs_get_device_parent: opens up given device's parent and returns a 
+ *     reference to its sysfs_device
+ * @dev: sysfs_device whose parent is requested
+ * Returns sysfs_device of the parent on success and NULL on failure
+ */
+struct sysfs_device *sysfs_get_device_parent(struct sysfs_device *dev)
+{
+       unsigned char ppath[SYSFS_PATH_MAX], *tmp = NULL;
+
+       if (dev == NULL) {
+               errno = EINVAL;
+               return NULL;
+       }
+
+       if (dev->parent != NULL)
+               return (dev->parent);
+
+       memset(ppath, 0, SYSFS_PATH_MAX);
+       strcpy(ppath, dev->path);
+       tmp = strrchr(ppath, '/');
+       if (tmp == NULL) {
+               dprintf("Invalid path to device %s\n", ppath);
+               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;
+       if (*(tmp +1) == '\0') {
+               *tmp = '\0';
+               tmp = strrchr(tmp, '/');
+               if (tmp == NULL) {
+                       dprintf("Invalid path to device %s\n", ppath);
+                       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;
+       *tmp = '\0';
+       
+       /*
+        * All "devices" have the "detach_state" attribute - validate here
+        */
+       strcat(ppath, "/detach_state");
+       if ((sysfs_path_is_file(ppath)) != 0) {
+               dprintf("Device at %s does not have a parent\n", dev->path);
+               return NULL;

        }
        }

-       sysfs_close_attribute(attribute);
-       return 0;
+       tmp = strrchr(ppath, '/');
+       *tmp = '\0';
+       dev->parent = sysfs_open_device_path(ppath);
+       if (dev->parent == NULL) {
+               dprintf("Error opening device %s's parent at %s\n", 
+                                       dev->bus_id, ppath);
+               return NULL;
+       }
+       return (dev->parent);

 }
 
 }
 

-/**
- * 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];
 {
        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;
                errno = EINVAL;

-               return -1;
+               return NULL;

        }
        }

-       
+

        memset(devpath, 0, SYSFS_PATH_MAX);
        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",
        }
        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",
        }
        if ((sysfs_read_attribute(attribute)) != 0) {
                dprintf("Error reading attribute %s for device %s\n",

-                               attrib, dev);
+                               attrib, bus_id);

                sysfs_close_attribute(attribute);
                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;

 }
 }

+