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sysfs_dir.c

/*
 * sysfs_dir.c
 *
 * Directory utility functions for libsysfs
 *
 * Copyright (C) IBM Corp. 2003
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 */
#include "libsysfs.h"
#include "sysfs.h"

/**
 * sysfs_del_attribute: routine for dlist integration
 */
static void sysfs_del_attribute(void *attr)
{
        sysfs_close_attribute((struct sysfs_attribute *)attr);
}

/**
 * sysfs_del_link: routine for dlist integration
 */
static void sysfs_del_link(void *ln)
{
        sysfs_close_link((struct sysfs_link *)ln);
}

/**
 * sysfs_del_dir: routine for dlist integration
 */
static void sysfs_del_directory(void *dir)
{
        sysfs_close_directory((struct sysfs_directory *)dir);
}

/**
 * dir_attribute_name_equal: compares dir attributes by name
 * @a: attribute name for comparison
 * @b: sysfs_attribute to be compared.
 * returns 1 if a==b->name or 0 if not equal
 */
static int dir_attribute_name_equal(void *a, void *b)
{
      if (a == NULL || b == NULL)
            return 0;

      if (strcmp(((char *)a), ((struct sysfs_attribute *)b)->name) == 0)
            return 1;

      return 0;
}

/**
 * dir_link_name_equal: compares dir links by name
 * @a: link name for comparison
 * @b: sysfs_link to be compared.
 * returns 1 if a==b->name or 0 if not equal
 */
static int dir_link_name_equal(void *a, void *b)
{
      if (a == NULL || b == NULL)
            return 0;

      if (strcmp(((char *)a), ((struct sysfs_link *)b)->name) == 0)
            return 1;

      return 0;
}

/**
 * dir_subdir_name_equal: compares subdirs by name
 * @a: name of subdirectory to compare
 * @b: sysfs_directory subdirectory to be compared
 * returns 1 if a==b->name or 0 if not equal
 */
static int dir_subdir_name_equal(void *a, void *b)
{
      if (a == NULL || b == NULL)
            return 0;

      if (strcmp(((char *)a), ((struct sysfs_directory *)b)->name) == 0)
            return 1;

      return 0;
}

/**
 * sysfs_close_attribute: closes and cleans up attribute
 * @sysattr: attribute to close.
 */
void sysfs_close_attribute(struct sysfs_attribute *sysattr)
{
      if (sysattr != NULL) {
            if (sysattr->value != NULL && sysattr->value[0] != '\0') /* davidz: latter is a stopgap fix */
                  free(sysattr->value);
            free(sysattr);
      }
}

/**
 * alloc_attribute: allocates and initializes attribute structure
 * returns struct sysfs_attribute with success and NULL with error.
 */
static struct sysfs_attribute *alloc_attribute(void)
{
      return (struct sysfs_attribute *)
                  calloc(1, sizeof(struct sysfs_attribute));
}

/**
 * sysfs_open_attribute: creates sysfs_attribute structure
 * @path: path to attribute.
 * returns sysfs_attribute struct with success and NULL with error.
 */
struct sysfs_attribute *sysfs_open_attribute(const char *path)
{
      struct sysfs_attribute *sysattr = NULL;
      struct stat fileinfo;
      
      if (path == NULL) {
            errno = EINVAL;
            return NULL;
      }
      sysattr = alloc_attribute();
      if (sysattr == NULL) {
            dprintf("Error allocating attribute at %s\n", path);
            return NULL;
      }
      if (sysfs_get_name_from_path(path, sysattr->name, 
                        SYSFS_NAME_LEN) != 0) {
            dprintf("Error retrieving attrib name from path: %s\n", path);
            sysfs_close_attribute(sysattr);
            return NULL;
      }
      safestrcpy(sysattr->path, path);
      if ((stat(sysattr->path, &fileinfo)) != 0) {
            dprintf("Stat failed: No such attribute?\n");
            sysattr->method = 0;
            free(sysattr);
            sysattr = NULL;
      } else {
            if (fileinfo.st_mode & S_IRUSR)
                  sysattr->method |= SYSFS_METHOD_SHOW;
            if (fileinfo.st_mode & S_IWUSR)
                  sysattr->method |= SYSFS_METHOD_STORE;
      }

      return sysattr;
}

/**
 * sysfs_write_attribute: write value to the attribute
 * @sysattr: attribute to write
 * @new_value: value to write
 * @len: length of "new_value"
 * returns 0 with success and -1 with error.
 */
int sysfs_write_attribute(struct sysfs_attribute *sysattr,
            const char *new_value, size_t len)
{
      int fd;
      int length;
      
      if (sysattr == NULL || new_value == NULL || len == 0) {
            errno = EINVAL;
            return -1;
      }
      
      if (!(sysattr->method & SYSFS_METHOD_STORE)) {
            dprintf ("Store method not supported for attribute %s\n",
                  sysattr->path);
            errno = EACCES;
            return -1;
      }
      if (sysattr->method & SYSFS_METHOD_SHOW) {
            /*
             * read attribute again to see if we can get an updated value 
             */
            if ((sysfs_read_attribute(sysattr)) != 0) {
                  dprintf("Error reading attribute\n");
                  return -1;
            }
            if ((strncmp(sysattr->value, new_value, sysattr->len)) == 0) {
                  dprintf("Attr %s already has the requested value %s\n",
                              sysattr->name, new_value);
                  return 0;   
            }
      }
      /* 
       * open O_WRONLY since some attributes have no "read" but only
       * "write" permission 
       */ 
      if ((fd = open(sysattr->path, O_WRONLY)) < 0) {
            dprintf("Error reading attribute %s\n", sysattr->path);
            return -1;
      }

      length = write(fd, new_value, len);
      if (length < 0) {
            dprintf("Error writing to the attribute %s - invalid value?\n",
                  sysattr->name);
            close(fd);
            return -1;
      } else if ((unsigned int)length != len) {
            dprintf("Could not write %d bytes to attribute %s\n", 
                              len, sysattr->name);
            /* 
             * since we could not write user supplied number of bytes,
             * restore the old value if one available
             */
            if (sysattr->method & SYSFS_METHOD_SHOW) {
                  length = write(fd, sysattr->value, sysattr->len);
                  close(fd);
                  return -1;
            }
      }
      
      /*
       * Validate length that has been copied. Alloc appropriate area
       * in sysfs_attribute. Verify first if the attribute supports reading
       * (show method). If it does not, do not bother
       */ 
      if (sysattr->method & SYSFS_METHOD_SHOW) {
            if (length != sysattr->len) {
                  sysattr->value = (char *)realloc
                        (sysattr->value, length);
                  sysattr->len = length;
                  safestrcpymax(sysattr->value, new_value, length);
            } else {
                  /*"length" of the new value is same as old one */ 
                  safestrcpymax(sysattr->value, new_value, length);
            }
      }
                  
      close(fd);  
      return 0;
}

/**
 * sysfs_read_attribute: reads value from attribute
 * @sysattr: attribute to read
 * returns 0 with success and -1 with error.
 */
int sysfs_read_attribute(struct sysfs_attribute *sysattr)
{
      char *fbuf = NULL;
      char *vbuf = NULL;
      ssize_t length = 0;
      long pgsize = 0;
      int fd;

      if (sysattr == NULL) {
            errno = EINVAL;
            return -1;
      }
      if (!(sysattr->method & SYSFS_METHOD_SHOW)) {
            dprintf("Show method not supported for attribute %s\n",
                  sysattr->path);
            errno = EACCES;
            return -1;
      }
      pgsize = sysconf(_SC_PAGESIZE);
      fbuf = (char *)calloc(1, pgsize+1);
      if (fbuf == NULL) {
            dprintf("calloc failed\n");
            return -1;
      }
      if ((fd = open(sysattr->path, O_RDONLY)) < 0) {
            dprintf("Error reading attribute %s\n", sysattr->path);
            free(fbuf);
            return -1;
      }
      length = read(fd, fbuf, pgsize);
      if (length < 0) {
            dprintf("Error reading from attribute %s\n", sysattr->path);
            close(fd);
            free(fbuf);
            return -1;
      }
      if (sysattr->len > 0) {
            if ((sysattr->len == length) && 
                        (!(strncmp(sysattr->value, fbuf, length)))) {
                  close(fd);
                  free(fbuf);
                  return 0;
            }
            free(sysattr->value);
      }
      sysattr->len = length;
      close(fd);
      vbuf = (char *)realloc(fbuf, length+1);
      if (vbuf == NULL) {
            dprintf("realloc failed\n");
            free(fbuf);
            return -1;
      }
      sysattr->value = vbuf;

      return 0;
}

/**
 * sysfs_read_attribute_value: given path to attribute, return its value.
 *    values can be up to a pagesize, if buffer is smaller the value will 
 *    be truncated. 
 * @attrpath: sysfs path to attribute
 * @value: buffer to put value
 * @vsize: size of value buffer
 * returns 0 with success and -1 with error.
 */
int sysfs_read_attribute_value(const char *attrpath, 
                              char *value, size_t vsize)
{
      struct sysfs_attribute *attr = NULL;
      size_t length = 0;

      if (attrpath == NULL || value == NULL || vsize == 0) {
            errno = EINVAL;
            return -1;
      }

      attr = sysfs_open_attribute(attrpath);
      if (attr == NULL) {
            dprintf("Invalid attribute path %s\n", attrpath);
            errno = EINVAL;
            return -1;
      }
      if((sysfs_read_attribute(attr)) != 0 || attr->value == NULL) {
            dprintf("Error reading from attribute %s\n", attrpath);
            sysfs_close_attribute(attr);
            return -1;
      }
      length = strlen(attr->value);
      if (length > vsize) 
            dprintf("Value length %d is larger than supplied buffer %d\n",
                  length, vsize);
      safestrcpymax(value, attr->value, vsize);
      sysfs_close_attribute(attr);

      return 0;
}

/**
 * sysfs_get_value_from_attrbutes: given a linked list of attributes and an 
 *    attribute name, return its value
 * @attr: attribute to search
 * @name: name to look for
 * returns char * value - could be NULL
 */
char *sysfs_get_value_from_attributes(struct dlist *attr, const char *name)
{     
      struct sysfs_attribute *cur = NULL;
      
      if (attr == NULL || name == NULL) {
            errno = EINVAL;
            return NULL;
      }
      dlist_for_each_data(attr, cur, struct sysfs_attribute) {
            if (strcmp(cur->name, name) == 0)
                  return cur->value;
      }
      return NULL;
}

/**
 * sysfs_close_link: closes and cleans up link.
 * @ln: link to close.
 */
void sysfs_close_link(struct sysfs_link *ln)
{
      if (ln != NULL) 
            free(ln);
}

/**
 * sysfs_close_directory: closes directory, cleans up attributes and links
 * @sysdir: sysfs_directory to close
 */
void sysfs_close_directory(struct sysfs_directory *sysdir)
{
      if (sysdir != NULL) {
            if (sysdir->subdirs != NULL) 
                  dlist_destroy(sysdir->subdirs);
            if (sysdir->links != NULL)
                  dlist_destroy(sysdir->links);
            if (sysdir->attributes != NULL) 
                  dlist_destroy(sysdir->attributes);
            free(sysdir);
            sysdir = NULL;
      }
}

/**
 * alloc_directory: allocates and initializes directory structure
 * returns struct sysfs_directory with success or NULL with error.
 */
static struct sysfs_directory *alloc_directory(void)
{
      return (struct sysfs_directory *)
                  calloc(1, sizeof(struct sysfs_directory));
}

/**
 * alloc_link: allocates and initializes link structure
 * returns struct sysfs_link with success or NULL with error.
 */
static struct sysfs_link *alloc_link(void)
{
      return (struct sysfs_link *)calloc(1, sizeof(struct sysfs_link));
}

/**
 * sysfs_read_all_subdirs: calls sysfs_read_directory for all subdirs
 * @sysdir: directory whose subdirs need reading.
 * returns 0 with success and -1 with error.
 */
int sysfs_read_all_subdirs(struct sysfs_directory *sysdir)
{
      struct sysfs_directory *cursub = NULL;
      int retval = 0;

      if (sysdir == NULL) {
            errno = EINVAL;
            return -1;
      }
      if (sysdir->subdirs == NULL) 
            if ((sysfs_read_dir_subdirs(sysdir)) != 0) 
                  return 0;
      if (sysdir->subdirs != NULL) {
            dlist_for_each_data(sysdir->subdirs, cursub, 
                                    struct sysfs_directory) {
                  if ((sysfs_read_dir_subdirs(cursub)) != 0) {
                        dprintf ("Error reading subdirectory %s\n",
                                    cursub->name);
                        retval = -1;
                  }
            }
      }
      if (!retval)
            errno = 0;
      return retval;
}

/**
 * sysfs_open_directory: opens a sysfs directory, creates dir struct, and
 *          returns.
 * @path: path of directory to open.
 * returns: struct sysfs_directory * with success and NULL on error.
 */
struct sysfs_directory *sysfs_open_directory(const char *path)
{
      struct sysfs_directory *sdir = NULL;

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

      if (sysfs_path_is_dir(path) != 0) {
            dprintf("Invalid path to directory %s\n", path);
            errno = EINVAL;
            return NULL;
      }

      sdir = alloc_directory();
      if (sdir == NULL) {
            dprintf("Error allocating directory %s\n", path);
            return NULL;
      }
      if (sysfs_get_name_from_path(path, sdir->name, SYSFS_NAME_LEN) != 0) {
            dprintf("Error getting directory name from path: %s\n", path);
            sysfs_close_directory(sdir);
            return NULL;
      }
      safestrcpy(sdir->path, path);

      return sdir;
}

/**
 * sysfs_open_link: opens a sysfs link, creates struct, and returns
 * @path: path of link to open.
 * returns: struct sysfs_link * with success and NULL on error.
 */
struct sysfs_link *sysfs_open_link(const char *linkpath)
{
      struct sysfs_link *ln = NULL;

      if (linkpath == NULL || strlen(linkpath) > SYSFS_PATH_MAX) {
            errno = EINVAL;
            return NULL;
      }

      ln = alloc_link();
      if (ln == NULL) {
            dprintf("Error allocating link %s\n", linkpath);
            return NULL;
      }
      safestrcpy(ln->path, linkpath);
      if ((sysfs_get_name_from_path(linkpath, ln->name, SYSFS_NAME_LEN)) != 0
          || (sysfs_get_link(linkpath, ln->target, SYSFS_PATH_MAX)) != 0) {
            sysfs_close_link(ln);
            errno = EINVAL;
            dprintf("Invalid link path %s\n", linkpath);
            return NULL;
      }

      return ln;
}

/**
 * add_attribute: open and add attribute at path to given directory
 * @sysdir: directory to add attribute to
 * @path: path to attribute
 * returns 0 with success and -1 with error.
 */
static int add_attribute(struct sysfs_directory *sysdir, const char *path)
{
      struct sysfs_attribute *attr = NULL;

      attr = sysfs_open_attribute(path);
      if (attr == NULL) {
            dprintf("Error opening attribute %s\n",   path);
            return -1;
      }
      if (attr->method & SYSFS_METHOD_SHOW) {
            if ((sysfs_read_attribute(attr)) != 0) {
                  dprintf("Error reading attribute %s\n",   path);
                  sysfs_close_attribute(attr);
                  return 0;
            }
      }
                                          
      if (sysdir->attributes == NULL) {
            sysdir->attributes = dlist_new_with_delete
                  (sizeof(struct sysfs_attribute), sysfs_del_attribute);
      }
      dlist_unshift_sorted(sysdir->attributes, attr, sort_list);

      return 0;
}

/**
 * add_subdirectory: open and add subdirectory at path to given directory
 * @sysdir: directory to add subdir to
 * @path: path to subdirectory
 * returns 0 with success and -1 with error.
 */
static int add_subdirectory(struct sysfs_directory *sysdir, const char *path)
{
      struct sysfs_directory *subdir = NULL;

      subdir = sysfs_open_directory(path);
      if (subdir == NULL) {
            dprintf("Error opening directory %s\n", path);
            return -1;
      }
      if (sysdir->subdirs == NULL)
            sysdir->subdirs = dlist_new_with_delete
                  (sizeof(struct sysfs_directory), sysfs_del_directory);
      dlist_unshift_sorted(sysdir->subdirs, subdir, sort_list);
      return 0;
}

/**
 * add_link: open and add link at path to given directory
 * @sysdir: directory to add link to
 * @path: path to link
 * returns 0 with success and -1 with error.
 */
static int add_link(struct sysfs_directory *sysdir, const char *path)
{
      struct sysfs_link *ln = NULL;

      ln = sysfs_open_link(path);
      if (ln == NULL) {
            dprintf("Error opening link %s\n", path);
            return -1;
      }
      if (sysdir->links == NULL)
            sysdir->links = dlist_new_with_delete
                        (sizeof(struct sysfs_link), sysfs_del_link);
      dlist_unshift_sorted(sysdir->links, ln, sort_list);
      return 0;
}

/**
 * sysfs_read_dir_attributes: grabs attributes for the given directory
 * @sysdir: sysfs directory to open
 * returns 0 with success and -1 with error.
 */
int sysfs_read_dir_attributes(struct sysfs_directory *sysdir)
{
      DIR *dir = NULL;
      struct dirent *dirent = NULL;
      char file_path[SYSFS_PATH_MAX];
      int retval = 0;

      if (sysdir == NULL) {
            errno = EINVAL;
            return -1;
      }
      dir = opendir(sysdir->path);
      if (dir == NULL) {
            dprintf("Error opening directory %s\n", sysdir->path);
            return -1;
      }
      while(((dirent = readdir(dir)) != NULL) && retval == 0) {
            if (0 == strcmp(dirent->d_name, "."))
                   continue;
            if (0 == strcmp(dirent->d_name, ".."))
                  continue;
            memset(file_path, 0, SYSFS_PATH_MAX);
            safestrcpy(file_path, sysdir->path);
            safestrcat(file_path, "/");
            safestrcat(file_path, dirent->d_name);
            if ((sysfs_path_is_file(file_path)) == 0)
                  retval = add_attribute(sysdir, file_path);
      }
      closedir(dir);
      if (!retval)
            errno = 0;
      return(retval);
}

/**
 * sysfs_read_dir_links: grabs links in a specific directory
 * @sysdir: sysfs directory to read links
 * returns 0 with success and -1 with error.
 */
int sysfs_read_dir_links(struct sysfs_directory *sysdir)
{
      DIR *dir = NULL;
      struct dirent *dirent = NULL;
      char file_path[SYSFS_PATH_MAX];
      int retval = 0;

      if (sysdir == NULL) {
            errno = EINVAL;
            return -1;
      }
      dir = opendir(sysdir->path);
      if (dir == NULL) {
            dprintf("Error opening directory %s\n", sysdir->path);
            return -1;
      }
      while(((dirent = readdir(dir)) != NULL) && retval == 0) {
            if (0 == strcmp(dirent->d_name, "."))
                   continue;
            if (0 == strcmp(dirent->d_name, ".."))
                  continue;
            memset(file_path, 0, SYSFS_PATH_MAX);
            safestrcpy(file_path, sysdir->path);
            safestrcat(file_path, "/");
            safestrcat(file_path, dirent->d_name);
            if ((sysfs_path_is_link(file_path)) == 0) {
                  retval = add_link(sysdir, file_path);
                  if (retval != 0)
                        break;
            }
      }
      closedir(dir);
      if (!retval)
            errno = 0;
      return(retval);
}

/**
 * sysfs_read_dir_subdirs: grabs subdirs in a specific directory
 * @sysdir: sysfs directory to read links
 * returns 0 with success and -1 with error.
 */
int sysfs_read_dir_subdirs(struct sysfs_directory *sysdir)
{
      DIR *dir = NULL;
      struct dirent *dirent = NULL;
      char file_path[SYSFS_PATH_MAX];
      int retval = 0;

      if (sysdir == NULL) {
            errno = EINVAL;
            return -1;
      }
      dir = opendir(sysdir->path);
      if (dir == NULL) {
            dprintf("Error opening directory %s\n", sysdir->path);
            return -1;
      }
      while(((dirent = readdir(dir)) != NULL) && retval == 0) {
            if (0 == strcmp(dirent->d_name, "."))
                   continue;
            if (0 == strcmp(dirent->d_name, ".."))
                  continue;
            memset(file_path, 0, SYSFS_PATH_MAX);
            safestrcpy(file_path, sysdir->path);
            safestrcat(file_path, "/");
            safestrcat(file_path, dirent->d_name);
            if ((sysfs_path_is_dir(file_path)) == 0)
                  retval = add_subdirectory(sysdir, file_path);
      }
      closedir(dir);
      if (!retval)
            errno = 0;
      return(retval);
}

/**
 * sysfs_read_directory: grabs attributes, links, and subdirectories
 * @sysdir: sysfs directory to open
 * returns 0 with success and -1 with error.
 */
int sysfs_read_directory(struct sysfs_directory *sysdir)
{
      DIR *dir = NULL;
      struct dirent *dirent = NULL;
      struct stat astats;
      char file_path[SYSFS_PATH_MAX];
      int retval = 0;

      if (sysdir == NULL) {
            errno = EINVAL;
            return -1;
      }
      dir = opendir(sysdir->path);
      if (dir == NULL) {
            dprintf("Error opening directory %s\n", sysdir->path);
            return -1;
      }
      while(((dirent = readdir(dir)) != NULL) && retval == 0) {
            if (0 == strcmp(dirent->d_name, "."))
                   continue;
            if (0 == strcmp(dirent->d_name, ".."))
                  continue;
            memset(file_path, 0, SYSFS_PATH_MAX);
            safestrcpy(file_path, sysdir->path);
            safestrcat(file_path, "/");
            safestrcat(file_path, dirent->d_name);
            if ((lstat(file_path, &astats)) != 0) {
                  dprintf("stat failed\n");
                  continue;
            }
            if (S_ISDIR(astats.st_mode)) 
                  retval = add_subdirectory(sysdir, file_path);

            else if (S_ISLNK(astats.st_mode))
                  retval = add_link(sysdir, file_path);

            else if (S_ISREG(astats.st_mode))
                  retval = add_attribute(sysdir, file_path);
      }
      closedir(dir);
      if (!retval)
            errno = 0;
      return(retval);
}

/**
 * sysfs_refresh_dir_attributes: Refresh attributes list
 * @sysdir: directory whose list of attributes to refresh
 * Returns 0 on success, 1 on failure
 */
int sysfs_refresh_dir_attributes(struct sysfs_directory *sysdir)
{
      if (sysdir == NULL) {
            errno = EINVAL;
            return 1;
      }
      if ((sysfs_path_is_dir(sysdir->path)) != 0) {
            dprintf("Invalid path to directory %s\n", sysdir->path);
            errno = EINVAL;
            return 1;
      }
      if (sysdir->attributes != NULL) {
            dlist_destroy(sysdir->attributes);
            sysdir->attributes = NULL;
      }
      if ((sysfs_read_dir_attributes(sysdir)) != 0) {
            dprintf("Error refreshing attributes for directory %s\n", 
                                          sysdir->path);
            return 1;
      }
      errno = 0;
      return 0;
}

/**
 * sysfs_refresh_dir_links: Refresh links list
 * @sysdir: directory whose list of links to refresh
 * Returns 0 on success, 1 on failure
 */
int sysfs_refresh_dir_links(struct sysfs_directory *sysdir)
{
      if (sysdir == NULL) {
            errno = EINVAL;
            return 1;
      }
      if ((sysfs_path_is_dir(sysdir->path)) != 0) {
            dprintf("Invalid path to directory %s\n", sysdir->path);
            errno = EINVAL;
            return 1;
      }
      if (sysdir->links != NULL) {
            dlist_destroy(sysdir->links);
            sysdir->links = NULL;
      }
      if ((sysfs_read_dir_links(sysdir)) != 0) {
            dprintf("Error refreshing links for directory %s\n", 
                                          sysdir->path);
            return 1;
      }
      errno = 0;
      return 0;
}

/**
 * sysfs_refresh_dir_subdirs: Refresh subdirs list
 * @sysdir: directory whose list of subdirs to refresh
 * Returns 0 on success, 1 on failure
 */
int sysfs_refresh_dir_subdirs(struct sysfs_directory *sysdir)
{
      if (sysdir == NULL) {
            errno = EINVAL;
            return 1;
      }
      if ((sysfs_path_is_dir(sysdir->path)) != 0) {
            dprintf("Invalid path to directory %s\n", sysdir->path);
            errno = EINVAL;
            return 1;
      }
      if (sysdir->subdirs != NULL) {
            dlist_destroy(sysdir->subdirs);
            sysdir->subdirs = NULL;
      }
      if ((sysfs_read_dir_subdirs(sysdir)) != 0) {
            dprintf("Error refreshing subdirs for directory %s\n", 
                                          sysdir->path);
            return 1;
      }
      errno = 0;
      return 0;
}

/**
 * sysfs_get_directory_attribute: retrieves attribute attrname from current
 *    directory only
 * @dir: directory to retrieve attribute from
 * @attrname: name of attribute to look for
 *
 * NOTE: Since we know the attribute to look for, this routine looks for the
 *    attribute if it was created _after_ the attrlist was read initially.
 *    
 * returns sysfs_attribute if found and NULL if not found
 */
struct sysfs_attribute *sysfs_get_directory_attribute
                  (struct sysfs_directory *dir, char *attrname)
{
      struct sysfs_attribute *attr = NULL;
      char new_path[SYSFS_PATH_MAX];
      
      if (dir == NULL || attrname == NULL) {
            errno = EINVAL;
            return NULL;
      }

      if (dir->attributes == NULL) 
            if ((sysfs_read_dir_attributes(dir) != 0) 
                || (dir->attributes == NULL))
                  return NULL;

      attr = (struct sysfs_attribute *)dlist_find_custom
                  (dir->attributes, attrname, dir_attribute_name_equal);
      if (attr != NULL) {
            if ((attr->method & SYSFS_METHOD_SHOW) &&
                  (sysfs_read_attribute(attr)) != 0) {
                  dprintf("Error reading attribute %s\n", attr->name);
                  return NULL;
            }
      } else {
            memset(new_path, 0, SYSFS_PATH_MAX);
            safestrcpy(new_path, dir->path);
            safestrcat(new_path, "/");
            safestrcat(new_path, attrname);
            if ((sysfs_path_is_file(new_path)) == 0) {
                  if ((add_attribute(dir, new_path)) == 0) {
                        attr = (struct sysfs_attribute *)
                              dlist_find_custom(dir->attributes,
                              attrname, dir_attribute_name_equal);
                  }
            }
      }
            
      return attr;
}

/**
 * sysfs_get_directory_link: retrieves link from one directory list
 * @dir: directory to retrieve link from
 * @linkname: name of link to look for
 * returns reference to sysfs_link if found and NULL if not found
 */
struct sysfs_link *sysfs_get_directory_link
                  (struct sysfs_directory *dir, char *linkname)
{
      if (dir == NULL || linkname == NULL) {
            errno = EINVAL;
            return NULL;
      }
      if (dir->links == NULL) {
            if ((sysfs_read_dir_links(dir) != 0) || (dir->links == NULL))
                  return NULL;
      } else {
            if ((sysfs_refresh_dir_links(dir)) != 0) 
                  return NULL;
      }

      return (struct sysfs_link *)dlist_find_custom(dir->links,
            linkname, dir_link_name_equal);
}

/**
 * sysfs_get_subdirectory: retrieves subdirectory by name.
 * @dir: directory to search for subdirectory.
 * @subname: subdirectory name to get.
 * returns reference to subdirectory or NULL if not found
 */
struct sysfs_directory *sysfs_get_subdirectory(struct sysfs_directory *dir,
                                    char *subname)
{
      struct sysfs_directory *sub = NULL, *cursub = NULL;

      if (dir == NULL || subname == NULL) {
            errno = EINVAL;
            return NULL;
      }

      if (dir->subdirs == NULL)
            if (sysfs_read_dir_subdirs(dir) != 0)
                  return NULL;

      sub = (struct sysfs_directory *)dlist_find_custom(dir->subdirs,
            subname, dir_subdir_name_equal);
      if (sub != NULL) 
            return sub;

      if (dir->subdirs != NULL) {
            dlist_for_each_data(dir->subdirs, cursub, 
                              struct sysfs_directory) {
                  if (cursub->subdirs == NULL) {
                        if (sysfs_read_dir_subdirs(cursub) != 0)
                              continue;
                        if (cursub->subdirs == NULL)
                              continue;
                  }
                  sub = sysfs_get_subdirectory(cursub, subname);
                  if (sub != NULL)
                        return sub;
            }
      }
      return NULL;
}

/**
 * sysfs_get_subdirectory_link: looks through all subdirs for specific link.
 * @dir: directory and subdirectories to search for link.
 * @linkname: link name to get.
 * returns reference to link or NULL if not found
 */
struct sysfs_link *sysfs_get_subdirectory_link(struct sysfs_directory *dir,
                                    char *linkname)
{
      struct sysfs_directory *cursub = NULL;
      struct sysfs_link *ln = NULL;

      if (dir == NULL || linkname == NULL) {
            errno = EINVAL;
            return NULL;
      }

      ln = sysfs_get_directory_link(dir, linkname);
      if (ln != NULL)
            return ln;

      if (dir->subdirs == NULL) 
            if (sysfs_read_dir_subdirs(dir) != 0)
                  return NULL;

      if (dir->subdirs != NULL) {
            dlist_for_each_data(dir->subdirs, cursub, 
                                    struct sysfs_directory) {
                  ln = sysfs_get_subdirectory_link(cursub, linkname);
                  if (ln != NULL)
                        return ln;
            }
      }
      return NULL;
}

/**
 * sysfs_get_dir_attributes: returns dlist of directory attributes
 * @dir: directory to retrieve attributes from
 * returns dlist of attributes or NULL
 */
struct dlist *sysfs_get_dir_attributes(struct sysfs_directory *dir)
{
      if (dir == NULL) {
            errno = EINVAL;
            return NULL;
      }

      if (dir->attributes == NULL) {
            if (sysfs_read_dir_attributes(dir) != 0)
                  return NULL;
      }

      return (dir->attributes);
}

/**
 * sysfs_get_dir_links: returns dlist of directory links
 * @dir: directory to return links for
 * returns dlist of links or NULL
 */
struct dlist *sysfs_get_dir_links(struct sysfs_directory *dir)
{
      if (dir == NULL) {
            errno = EINVAL;
            return NULL;
      }

      if (dir->links == NULL) {
            if (sysfs_read_dir_links(dir) != 0)
                  return NULL;
      }

      return (dir->links);
}

/**
 * sysfs_get_dir_subdirs: returns dlist of directory subdirectories
 * @dir: directory to return subdirs for
 * returns dlist of subdirs or NULL
 */
struct dlist *sysfs_get_dir_subdirs(struct sysfs_directory *dir)
{
      if (dir == NULL) {
            errno = EINVAL;
            return NULL;
      }

      if (dir->subdirs == NULL) {
            if (sysfs_read_dir_subdirs(dir) != 0)
                  return NULL;
      }

      return (dir->subdirs);
}

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