chiark / gitweb /
[PATCH] big libsysfs diet (pre 2.0 version)
[elogind.git] / libsysfs / sysfs_device.c
index 2a5353e..7087730 100644 (file)
@@ -3,7 +3,7 @@
  *
  * Generic device utility functions for libsysfs
  *
- * Copyright (C) IBM Corp. 2003
+ * Copyright (C) IBM Corp. 2003-2005
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Lesser General Public
 #include "libsysfs.h"
 #include "sysfs.h"
 
-static int confirm_device_bus(struct sysfs_device *dev, 
-                               unsigned char *busname, unsigned char *bus_id)
+/**
+ * get_dev_driver: fills in the dev->driver_name field 
+ * Returns 0 on SUCCESS and -1 on error
+ */
+static int get_dev_driver(struct sysfs_device *dev)
 {
-        struct sysfs_link *devlink = NULL;
-        unsigned char devpath[SYSFS_PATH_MAX];
-       unsigned char *s = NULL;
-       int result = 0;
-
-        if (busname == NULL || bus_id == NULL)
-                return -1;
+       struct dlist *drvlist;
+       char path[SYSFS_PATH_MAX];
+       char devpath[SYSFS_PATH_MAX];
+       char *drv = NULL, *c;
 
-        if (sysfs_get_mnt_path(devpath, SYSFS_PATH_MAX) != 0)
-                return -1;
+       if (!dev) {
+               errno = EINVAL;
+               return -1;
+       }
 
-       s = &devpath[strlen(devpath)-1];
-       if (strncmp(s, "/", 1) == 0)
-               *s = '\0';
-        strcat(devpath, SYSFS_BUS_DIR);
-        strcat(devpath, "/");
-        strcat(devpath, busname);
-        strcat(devpath, SYSFS_DEVICES_DIR);
-        strcat(devpath, "/");
-        strcat(devpath, bus_id);
+       memset(path, 0, SYSFS_PATH_MAX);
+       memset(devpath, 0, SYSFS_PATH_MAX);
+       safestrcpymax(path, dev->path, SYSFS_PATH_MAX);
+       safestrcatmax(path, "/driver", SYSFS_PATH_MAX);
+       if (!sysfs_path_is_link(path)) {
+               if (!sysfs_get_link(path, devpath, SYSFS_PATH_MAX)) {
+                       if (sysfs_get_name_from_path(devpath, 
+                                       dev->driver_name, SYSFS_NAME_LEN))
+                               return -1;
+               }
+               return 0;
+       }
 
-       devlink = sysfs_open_link(devpath);
-       if (devlink == NULL)
+       /*
+        * Devices on on earlier kernels do not have the "driver" link.
+        * Look it up in the bus directory.
+        */
+       if (dev->bus[0] == '\0')
                return -1;
-
-       if (strcmp(devlink->target, dev->path) == 0)
-               result++;
-       sysfs_close_link(devlink);
-       return result;
+       memset(path, 0, SYSFS_PATH_MAX);
+       memset(devpath, 0, SYSFS_PATH_MAX);
+       safestrcpy(path, dev->path);
+       c = strstr(path, SYSFS_DEVICES_NAME);
+       if (c == NULL) {
+               dprintf("Invalid path to device - %s\n", dev->path);
+               return -1;
+       } else
+               *c = '\0';
+       safestrcat(path, SYSFS_BUS_NAME);
+       safestrcat(path, "/");
+       safestrcat(path, dev->bus);
+       safestrcat(path, "/");
+       safestrcat(path, SYSFS_DRIVERS_NAME);
+
+       drvlist = sysfs_open_directory_list(path);
+       if (drvlist) {
+               dlist_for_each_data(drvlist, drv, char) {
+                       safestrcpy(devpath, path);
+                       safestrcat(devpath, "/");
+                       safestrcat(devpath, drv);
+                       safestrcat(devpath, "/");
+                       safestrcat(devpath, dev->bus_id);
+                       if (sysfs_path_is_link(devpath) == 0) {
+                               safestrcpy(dev->driver_name, drv);
+                               sysfs_close_list(drvlist);
+                               return 0;
+                       }
+               }
+               sysfs_close_list(drvlist);
+       }
+       return -1;
 }
 
 /**
- * get_device_bus: retrieves the bus name the device is on, checks path to
- *     bus' link to make sure it has correct device.
+ * sysfs_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)
+int sysfs_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) {
+       char devpath[SYSFS_PATH_MAX];
+       char subsys[SYSFS_NAME_LEN];
+       char path[SYSFS_PATH_MAX];
+       char target[SYSFS_PATH_MAX];
+       char *bus = NULL, *c;
+       struct dlist *buslist;
+
+       if (!dev) {
                errno = EINVAL;
                return -1;
        }
 
-       strcpy(subsys, SYSFS_BUS_DIR);  /* subsys = /bus */
-       buslist = sysfs_open_subsystem_list(subsys);
-       if (buslist != NULL) {
+       memset(path, 0, SYSFS_PATH_MAX);
+       memset(devpath, 0, SYSFS_PATH_MAX);
+       safestrcpymax(path, dev->path, SYSFS_PATH_MAX);
+       safestrcatmax(path, "/bus", SYSFS_PATH_MAX);
+       if (!sysfs_path_is_link(path)) {
+               if (!sysfs_get_link(path, devpath, SYSFS_PATH_MAX)) {
+                       if (sysfs_get_name_from_path(devpath, 
+                                       dev->bus, SYSFS_NAME_LEN))
+                               return -1;
+               }
+               return 0;
+       }
+
+       /*
+        * Devices on on earlier kernels do not have the "bus" link.
+        * Look it up in the bus directory.
+        */
+       memset(subsys, 0, SYSFS_NAME_LEN);
+       safestrcpy(subsys, dev->path);
+       c = strstr(subsys, SYSFS_DEVICES_NAME);
+       if (c == NULL) {
+               dprintf("Invalid path to device - %s\n", dev->path);
+               return -1;
+       } else 
+               *c = '\0';
+       safestrcat(subsys, SYSFS_BUS_NAME);
+       buslist = sysfs_open_directory_list(subsys);
+       if (buslist) {
                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;
+                       memset(path, 0, SYSFS_PATH_MAX);
+                       safestrcpy(path, subsys);
+                       safestrcat(path, "/");
+                       safestrcat(path, bus);
+                       safestrcat(path, "/");
+                       safestrcat(path, SYSFS_DEVICES_NAME);
+                       safestrcat(path, "/");
+                       safestrcat(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)) {
+                                       dprintf("Error getting link target\n");
+                                       sysfs_close_list(buslist);
+                                       return -1;
+                               }
+                               if (!(strncmp(target, dev->path, 
+                                                       SYSFS_PATH_MAX))) {
+                                       safestrcpy(dev->bus, bus);
+                                       sysfs_close_list(buslist);
+                                       return 0;
+                               }
+                       }
+               }
+               sysfs_close_list(buslist);
+       }
+       return -1;
 }
 
 /**
@@ -103,10 +175,10 @@ static int get_device_bus(struct sysfs_device *dev)
  *     closing children only.
  * @devroot: device root of tree.
  */
-static void sysfs_close_device_tree(struct sysfs_device *devroot)
+void sysfs_close_device_tree(struct sysfs_device *devroot)
 {
-       if (devroot != NULL) {
-               if (devroot->children != NULL) {
+       if (devroot) {
+               if (devroot->children) {
                        struct sysfs_device *child = NULL;
 
                        dlist_for_each_data(devroot->children, child,
@@ -119,32 +191,18 @@ 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
- */
-static void sysfs_close_dev_tree(void *dev)
-{
-       sysfs_close_device_tree((struct sysfs_device *)dev);
-}
-
-/**
  * sysfs_close_device: closes and cleans up a device
  * @dev = device to clean up
  */
 void sysfs_close_device(struct sysfs_device *dev)
 {
-       if (dev != NULL) {
-               if (dev->directory != NULL)
-                       sysfs_close_directory(dev->directory);
-               if (dev->children != NULL && dev->children->count == 0)
+       if (dev) {
+               if (dev->parent)
+                       sysfs_close_device(dev->parent);
+               if (dev->children && dev->children->count)
                        dlist_destroy(dev->children);
+               if (dev->attrlist)
+                       dlist_destroy(dev->attrlist);
                free(dev);
        }
 }
@@ -155,265 +213,89 @@ void sysfs_close_device(struct sysfs_device *dev)
  */
 static struct sysfs_device *alloc_device(void)
 {
-       return (struct sysfs_device *)calloc(1, sizeof(struct sysfs_device));
-}
-
-/**
- * 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_attribute *sysfs_get_device_attr(struct sysfs_device *dev,
-                                               const unsigned char *name)
-{
-       struct sysfs_attribute *cur = NULL;
-
-       if (dev == NULL || dev->directory == NULL 
-           || dev->directory->attributes == NULL || name == NULL) {
-               errno = EINVAL;
-               return NULL;
-       }
-       
-       cur = sysfs_get_directory_attribute(dev->directory, 
-                       (unsigned char *)name);
-       if (cur != NULL)
-               return cur;
-
-       return NULL;
+       return (struct sysfs_device *) calloc(1, sizeof(struct sysfs_device));
 }
 
 /**
- * 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
  */
-struct sysfs_device *sysfs_open_device(const unsigned char *path)
+struct sysfs_device *sysfs_open_device_path(const char *path)
 {
-       struct sysfs_device *dev = NULL;
-       struct sysfs_directory *sdir = NULL;
+       struct sysfs_device *dev;
 
-       if (path == NULL) {
+       if (!path) {
                errno = EINVAL;
                return NULL;
        }
-       dev = alloc_device();   
-       if (dev == NULL) {
+       if (sysfs_path_is_dir(path)) {
+               dprintf("Incorrect path to device: %s\n", path);
+               return NULL;
+       }
+       dev = alloc_device();
+       if (!dev) {
                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)) {
                errno = EINVAL;
+               dprintf("Error getting device bus_id\n");
                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);
+       safestrcpy(dev->path, path);
+       if (sysfs_remove_trailing_slash(dev->path)) {
+               dprintf("Invalid path to device %s\n", dev->path);
                sysfs_close_device(dev);
                return NULL;
        }
-       dev->directory = sdir;
-       strcpy(dev->bus_id, sdir->name);
-       strcpy(dev->path, sdir->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.
         */
-       strncpy(dev->name, sdir->name, SYSFS_NAME_LEN);
-       
-       if (get_device_bus(dev) != 0)
-               strcpy(dev->bus, SYSFS_UNKNOWN);
-
-       return dev;
-}
+       safestrcpy(dev->name, dev->bus_id);
 
-/**
- * sysfs_open_device_tree: opens root device and all of its children,
- *     creating a tree of devices. Only opens children.
- * @path: sysfs path to devices
- * returns struct sysfs_device and its children with success or NULL with
- *     error.
- */
-static struct sysfs_device *sysfs_open_device_tree(const unsigned char *path)
-{
-       struct sysfs_device *rootdev = NULL, *new = NULL;
-       struct sysfs_directory *cur = NULL;
+       if (sysfs_get_device_bus(dev))
+               dprintf("Could not get device bus\n");
 
-       if (path == NULL) {
-               errno = EINVAL;
-               return NULL;
-       }
-       rootdev = sysfs_open_device(path);
-       if (rootdev == NULL) {
-               dprintf("Error opening root device at %s\n", path);
-               return NULL;
-       }
-       if (rootdev->directory->subdirs != NULL) {
-               dlist_for_each_data(rootdev->directory->subdirs, cur,
-                               struct sysfs_directory) {
-                       new = sysfs_open_device_tree(cur->path);
-                       if (new == NULL) {
-                               dprintf("Error opening device tree at %s\n",
-                                       cur->path);
-                               sysfs_close_device_tree(rootdev);
-                               return NULL;
-                       }
-                       if (rootdev->children == NULL)
-                               rootdev->children = dlist_new_with_delete
-                                       (sizeof(struct sysfs_device),
-                                       sysfs_del_device);
-                       dlist_unshift(rootdev->children, new);
-               }
+       if (get_dev_driver(dev)) {
+               dprintf("Could not get device %s's driver\n", dev->bus_id);
+               safestrcpy(dev->driver_name, SYSFS_UNKNOWN);
        }
 
-       return rootdev;
-}
-
-/**
- * sysfs_close_root_device: closes root and all devices
- * @root: root device to close
- */
-void sysfs_close_root_device(struct sysfs_root_device *root)
-{
-       if (root != NULL) {
-               if (root->devices != NULL)
-                       dlist_destroy(root->devices);
-               if (root->directory != NULL)
-                       sysfs_close_directory(root->directory);
-               free(root);
-       }
+       return dev;
 }
 
 /**
- * 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
+ * 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.
  */
-static struct sysfs_directory *open_root_device_dir(const unsigned char *name)
+struct sysfs_attribute *sysfs_get_device_attr(struct sysfs_device *dev,
+                                               const 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) {
+       if (!dev || !name) {
                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
- * @root: root device to open devices for
- * returns 0 with success and -1 with error
- */
-static int get_all_root_devices(struct sysfs_root_device *root)
-{
-       struct sysfs_device *dev = NULL;
-       struct sysfs_directory *cur = NULL;
-
-       if (root == NULL || root->directory == NULL) {
-               errno = EINVAL;
-               return -1;
-       }
-       if (root->directory->subdirs == NULL)
-               return 0;
-
-       dlist_for_each_data(root->directory->subdirs, cur,
-                       struct sysfs_directory) {
-               dev = sysfs_open_device_tree(cur->path);
-               if (dev == NULL) {
-                       dprintf ("Error opening device at %s\n", cur->path);
-                       continue;
-               }
-               if (root->devices == NULL)
-                       root->devices = dlist_new_with_delete
-                               (sizeof(struct sysfs_device), 
-                               sysfs_close_dev_tree);
-               dlist_unshift(root->devices, dev);
-       }
-
-       return 0;
+       return get_attribute(dev, (char *)name);
 }
 
 /**
- * sysfs_open_root_device: opens sysfs devices root and all of its
- *     devices.
- * @name: name of /sys/devices/root to open
- * returns struct sysfs_root_device if success and NULL with error
+ * sysfs_get_device_attributes: gets list of device attributes
+ * @dev: device whose attributes list is needed
+ * returns dlist of attributes on success or NULL on error
  */
-struct sysfs_root_device *sysfs_open_root_device(const unsigned char *name)
+struct dlist *sysfs_get_device_attributes(struct sysfs_device *dev)
 {
-       struct sysfs_root_device *root = NULL;
-       struct sysfs_directory *rootdir = NULL;
-
-       if (name == NULL) {
+       if (!dev) {
                errno = EINVAL;
                return NULL;
        }
-
-       root = (struct sysfs_root_device *)calloc
-                                       (1, sizeof(struct sysfs_root_device));
-       if (root == NULL) {
-               dprintf("calloc failure\n");
-               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);
-               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);
-               return NULL;
-       }
-
-       return root;
-}
-
-/**
- * sysfs_get_device_attributes: returns a dlist of attributes corresponding to
- *     the specific device
- * @device: struct sysfs_device * for which attributes are to be returned
- */
-struct dlist *sysfs_get_device_attributes(struct sysfs_device *device)
-{
-       if (device == NULL || device->directory == NULL) 
-               return NULL;
-
-       return (device->directory->attributes);
+       return get_attributes_list(dev);
 }
 
 /**
@@ -424,32 +306,34 @@ struct dlist *sysfs_get_device_attributes(struct sysfs_device *device)
  * @psize: size of "path"
  * Returns 0 on success -1 on failure
  */
-static int get_device_absolute_path(const unsigned char *device,
-               const unsigned char *bus, unsigned char *path, size_t psize)
+static int get_device_absolute_path(const char *device,        const char *bus, 
+                               char *path, size_t psize)
 {
-       unsigned char bus_path[SYSFS_NAME_LEN];
+       char bus_path[SYSFS_PATH_MAX];
 
-       if (device == NULL || path == NULL) {
+       if (!device || !path) {
                errno = EINVAL;
                return -1;
        }
 
-       memset(bus_path, 0, SYSFS_NAME_LEN);
-       if (sysfs_get_mnt_path(bus_path, SYSFS_PATH_MAX) != 0) {
+       memset(bus_path, 0, SYSFS_PATH_MAX);
+       if (sysfs_get_mnt_path(bus_path, SYSFS_PATH_MAX)) {
                dprintf ("Sysfs not supported on this system\n");
                return -1;
        }
-       strcat(bus_path, SYSFS_BUS_DIR);
-       strcat(bus_path, "/");
-       strcat(bus_path, bus);
-       strcat(bus_path, SYSFS_DEVICES_DIR);
-       strcat(bus_path, "/");
-       strcat(bus_path, device);
+       safestrcat(bus_path, "/");
+       safestrcat(bus_path, SYSFS_BUS_NAME);
+       safestrcat(bus_path, "/");
+       safestrcat(bus_path, bus);
+       safestrcat(bus_path, "/");
+       safestrcat(bus_path, SYSFS_DEVICES_NAME);
+       safestrcat(bus_path, "/");
+       safestrcat(bus_path, device);
        /*
         * We now are at /sys/bus/"bus_name"/devices/"device" which is a link.
         * Now read this link to reach to the device.
         */ 
-       if ((sysfs_get_link(bus_path, path, SYSFS_PATH_MAX)) != 0) {
+       if (sysfs_get_link(bus_path, path, psize)) {
                dprintf("Error getting to device %s\n", device);
                return -1;
        }
@@ -457,36 +341,34 @@ static int get_device_absolute_path(const unsigned char *device,
 }
 
 /**
- * sysfs_open_device_by_id: open a device by id (use the "bus" subsystem)
+ * sysfs_open_device: open a device by id (use the "bus" subsystem)
+ * @bus: bus the device belongs to
  * @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_device *sysfs_open_device(const char *bus,        const char *bus_id)
 {
        char sysfs_path[SYSFS_PATH_MAX];
-       struct sysfs_device *device = NULL;
+       struct sysfs_device *device;
 
-       if (bus_id == NULL || bus == NULL) {
+       if (!bus_id || !bus) {
                errno = EINVAL;
                return NULL;
        }
        memset(sysfs_path, 0, SYSFS_PATH_MAX);
-       if ((get_device_absolute_path(bus_id, bus, sysfs_path, 
-                                               SYSFS_PATH_MAX)) != 0) {
+       if (get_device_absolute_path(bus_id, bus, sysfs_path, 
+                               SYSFS_PATH_MAX)) {
                dprintf("Error getting to device %s\n", bus_id);
                return NULL;
        }
        
-       device = sysfs_open_device(sysfs_path);
-       if (device == NULL) {
+       device = sysfs_open_device_path(sysfs_path);
+       if (!device) {
                dprintf("Error opening device %s\n", bus_id);
                return NULL;
        }
@@ -494,48 +376,56 @@ struct sysfs_device *sysfs_open_device_by_id(const unsigned char *bus_id,
        return device;
 }
 
-/*
- * 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. 
+/**
+ * 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_attribute *sysfs_open_device_attr(const unsigned char *bus,
-               const unsigned char *bus_id, const unsigned char *attrib)
+struct sysfs_device *sysfs_get_device_parent(struct sysfs_device *dev)
 {
-       struct sysfs_attribute *attribute = NULL;
-       unsigned char devpath[SYSFS_PATH_MAX];
-       
-       if (bus == NULL || bus_id == NULL || attrib == NULL) {
+       char ppath[SYSFS_PATH_MAX], *tmp;
+
+       if (!dev) {
                errno = EINVAL;
                return NULL;
        }
 
-       memset(devpath, 0, SYSFS_PATH_MAX);
-       if ((get_device_absolute_path(bus_id, bus, devpath, 
-                                       SYSFS_PATH_MAX)) != 0) {
-               dprintf("Error getting to device %s\n", bus_id);
+       if (dev->parent)
+               return (dev->parent);
+
+       memset(ppath, 0, SYSFS_PATH_MAX);
+       safestrcpy(ppath, dev->path);
+       tmp = strrchr(ppath, '/');
+       if (!tmp) {
+               dprintf("Invalid path to device %s\n", ppath);
                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, bus_id);
+       if (*(tmp + 1) == '\0') {
+               *tmp = '\0';
+               tmp = strrchr(tmp, '/');
+               if (tmp == NULL) {
+                       dprintf("Invalid path to device %s\n", ppath);
+                       return NULL;
+               }
+       }
+       *tmp = '\0';
+
+       /*
+        * All "devices" have the "detach_state" attribute - validate here
+        */
+       safestrcat(ppath, "/detach_state");
+       if (sysfs_path_is_file(ppath)) {
+               dprintf("Device at %s does not have a parent\n", dev->path);
                return NULL;
        }
-       if ((sysfs_read_attribute(attribute)) != 0) {
-               dprintf("Error reading attribute %s for device %s\n",
-                               attrib, bus_id);
-               sysfs_close_attribute(attribute);
+       tmp = strrchr(ppath, '/');
+       *tmp = '\0';
+       dev->parent = sysfs_open_device_path(ppath);
+       if (!dev->parent) {
+               dprintf("Error opening device %s's parent at %s\n", 
+                                       dev->bus_id, ppath);
                return NULL;
        }
-       return attribute;
+       return (dev->parent);
 }
-