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#include <string.h>
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#include <sysfs/libsysfs.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <sys/sysmacros.h>
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#define DEV_BUFFER_LENGTH 20
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* helper function that compares the string dev against the
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* attribute "dev" in directory dir
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* returns 1 if match is found, else 0
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dir_matches_device(const char *dir, const char *dev) {
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int dev_attr_len, dev_parm_len, ret = 0;
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struct sysfs_attribute *devattr;
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char path[SYSFS_PATH_MAX];
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devattr = sysfs_open_attribute(path);
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sysfs_read_attribute(devattr);
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/* exclude white space from comparison */
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dev_attr_len = strspn(devattr->value, "1234567890:");
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dev_parm_len = strlen(dev);
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if (dev_attr_len != dev_parm_len )
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else if (!strncmp(dev,devattr->value, dev_parm_len))
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sysfs_close_attribute(devattr);
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#define PATH_BUFFER_LENGTH 256
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#define BLOCKPATH "/sys/block/"
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#define DEVICE_LINK "device"
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#define DEV_ATTRIBUTE "dev"
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* Helper function that expects a file name and returns 1 if this
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* is a directory or 0 otherwise.
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static int isdir(char *name) {
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if (lstat(name, &statbuf) < 0)
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return S_ISDIR(statbuf.st_mode);
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* Helper function that expects a directory name in sysfs of the form
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* /sys/block/<devname>/ or /sys/block/<devname>/<partname>/.
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* It will try to read the file "dev" in this directory and compare
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* it's contents with the given dev string of the form <major>:<minor>.
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* Trailing white space (newline) is ignored.
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* The buffer name is expected to be long enough to hold the additional "dev".
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* Returns 1 if the directory matches dev, 0 otherwise.
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static int check_directory(char *name, char *dev) {
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char buffer[DEV_BUFFER_LENGTH];
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int dev_attr_len, dev_parm_len, namelen;
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namelen = strlen(name);
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if ((PATH_BUFFER_LENGTH - namelen) < sizeof(DEV_ATTRIBUTE))
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strcpy(end, DEV_ATTRIBUTE);
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fd = open(name, O_RDONLY);
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count = read(fd, buffer, DEV_BUFFER_LENGTH);
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dev_attr_len = strspn(buffer, "1234567890:");
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dev_parm_len = strlen(dev);
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if (dev_attr_len != dev_parm_len )
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return (strncmp(dev, buffer, dev_parm_len) == 0);
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* Helper function that expects a directory name in sysfs of the form
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* /sys/block/<devname>/. It will try to read a link "device"
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* in this directory and extract the busid, which is the last part
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* of that link. The buffer name is expected to be long enough
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* to hold the additional "device".
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* name: block device path in sysfs.
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* busid: buffer in which the busid string will be returned
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* returns 0 for successfull operation and -1 in case of an error.
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static int extract_busid(char *name, char *busid) {
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char linkbuffer[PATH_BUFFER_LENGTH];
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namelen = strlen(name);
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if ((PATH_BUFFER_LENGTH - namelen) < sizeof(DEVICE_LINK))
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end = name + namelen;
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strcpy(end, DEVICE_LINK);
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count = readlink(name, linkbuffer, PATH_BUFFER_LENGTH - 1);
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linkbuffer[count] = 0;
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start = strrchr(linkbuffer, '/');
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strcpy(busid, start);
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* Helper function that makes some basic checks on a directory entry.
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* The function checks if there is still enough space left in the buffer
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* for the new string, excludes '.' and '..', and verifies that the entry
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* is actually a directory.
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* buffer: the beginning of the name buffer
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* oldend: the current end of the string in the name buffer
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* dir: the dirent in question
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* returns: a pointer to the new end of the string in buffer or NULL if
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* one of the checks failed
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static char *append_if_directory(char *buffer, char *oldend, struct dirent *dir) {
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int oldlength, dirlength;
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if (strcmp(dir->d_name, ".") == 0 ||
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strcmp(dir->d_name, "..") == 0)
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oldlength = strlen(buffer);
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dirlength = strlen(dir->d_name);
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if (PATH_BUFFER_LENGTH < oldlength + dirlength + 2)
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strcpy(oldend, dir->d_name);
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if (!isdir(buffer)) {
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newend = oldend + dirlength;
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* helper function that searches for a specific block device and returns
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* sysfs: structure that represents the sysfs root directory
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* dev: <major>:<minor> of the device
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* busid: buffer in which the busid string will be returned
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* returns 0 for successfull operation and -1 in case of an error.
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* returns 0 for successfull operation and -1 in case of an error.
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find_busid_in_sysfs(const char *sysfs, char *dev, char *busid) {
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char *dir, *subdir, *blkdevdir;
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struct dlist *blockdirs, *blocksubdirs;
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char path[SYSFS_PATH_MAX], path1[SYSFS_PATH_MAX];
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strcat(path, SYSFS_BLOCK_NAME);
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blockdirs = sysfs_open_directory_list(path);
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/* go through all directories and subdirectories in /sys/block
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* e.g. /sys/block/dasda as well as /sys/block/dasda1 etc.
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* match the attribute 'dev' against the string we build in
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static int find_busid_in_sysfs(char *dev, char *busid) {
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DIR *blockdir, *diskdir;
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struct dirent *blockde, *diskde;
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char namebuffer[PATH_BUFFER_LENGTH];
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char *blockend, *diskend = NULL, *partend;
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/* everything, including the other helper functions, works on the
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* same buffer area 'namebuffer'. The pointers blockend, diskend
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* and partend point to the end of the various names.
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* "/sys/block/dasda/dasda1/"
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dlist_for_each_data(blockdirs, dir, char) {
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blocksubdirs = sysfs_open_directory_list(dir);
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dlist_for_each_data(blocksubdirs, subdir, char) {
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strcat(path1, subdir);
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if (dir_matches_device(path1, dev)) {
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if (dir_matches_device(path1, dev)) {
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strcpy(namebuffer,BLOCKPATH);
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blockdir = opendir(namebuffer);
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blockend = namebuffer + strlen(namebuffer);
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/* check each entry in /sys/block */
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while ((blockde = readdir(blockdir))) {
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diskend = append_if_directory(namebuffer, blockend, blockde);
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found = check_directory(namebuffer, dev);
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diskdir = opendir(namebuffer);
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/* check each entry in /sys/block/<disk name> */
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while ((diskde = readdir(diskdir))) {
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partend = append_if_directory(
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namebuffer, diskend, diskde);
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found = check_directory(namebuffer, dev);
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* now that we have the right block device, we can follow the
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* link to the device and extract the busid
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strcpy(path, blkdevdir);
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strcat(path, "/device");
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sysfs_get_link(path, path1, SYSFS_PATH_MAX);
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if (sysfs_get_name_from_path(path1, busid, SYSFS_BUS_ID_SIZE))
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*diskend = 0; /* remove partition directory from name */
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return extract_busid(namebuffer, busid);
added
removed
libu2s/u2s.c
