diff options
Diffstat (limited to 'alsactl/init_sysfs.c')
| -rw-r--r-- | alsactl/init_sysfs.c | 158 |
1 files changed, 158 insertions, 0 deletions
diff --git a/alsactl/init_sysfs.c b/alsactl/init_sysfs.c new file mode 100644 index 0000000..0cbada2 --- /dev/null +++ b/alsactl/init_sysfs.c @@ -0,0 +1,158 @@ +/* + * Copyright (C) 2005-2006 Kay Sievers <kay.sievers@vrfy.org> + * 2008 Jaroslav Kysela <perex@perex.cz> + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License as published by the + * Free Software Foundation version 2 of the License. + * + * This program 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 + * General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. + * + */ + + +static char sysfs_path[PATH_SIZE]; + +/* attribute value cache */ +static LIST_HEAD(attr_list); +struct sysfs_attr { + struct list_head node; + char path[PATH_SIZE]; + char *value; /* points to value_local if value is cached */ + char value_local[NAME_SIZE]; +}; + +static int sysfs_init(void) +{ + const char *env; + char sysfs_test[PATH_SIZE]; + + env = getenv("SYSFS_PATH"); + if (env) { + strlcpy(sysfs_path, env, sizeof(sysfs_path)); + remove_trailing_chars(sysfs_path, '/'); + } else + strlcpy(sysfs_path, "/sys", sizeof(sysfs_path)); + dbg("sysfs_path='%s'", sysfs_path); + + strlcpy(sysfs_test, sysfs_path, sizeof(sysfs_test)); + strlcat(sysfs_test, "/kernel/uevent_helper", sizeof(sysfs_test)); + if (access(sysfs_test, F_OK)) { + error("sysfs path '%s' is invalid\n", sysfs_path); + return -errno; + } + + INIT_LIST_HEAD(&attr_list); + return 0; +} + +static void sysfs_cleanup(void) +{ + struct sysfs_attr *attr_loop; + struct sysfs_attr *attr_temp; + + list_for_each_entry_safe(attr_loop, attr_temp, &attr_list, node) { + list_del(&attr_loop->node); + free(attr_loop); + } +} + +static char *sysfs_attr_get_value(const char *devpath, const char *attr_name) +{ + char path_full[PATH_SIZE]; + const char *path; + char value[NAME_SIZE]; + struct sysfs_attr *attr_loop; + struct sysfs_attr *attr; + struct stat statbuf; + int fd; + ssize_t size; + size_t sysfs_len; + + dbg("open '%s'/'%s'", devpath, attr_name); + sysfs_len = strlcpy(path_full, sysfs_path, sizeof(path_full)); + path = &path_full[sysfs_len]; + strlcat(path_full, devpath, sizeof(path_full)); + strlcat(path_full, "/", sizeof(path_full)); + strlcat(path_full, attr_name, sizeof(path_full)); + + /* look for attribute in cache */ + list_for_each_entry(attr_loop, &attr_list, node) { + if (strcmp(attr_loop->path, path) == 0) { + dbg("found in cache '%s'", attr_loop->path); + return attr_loop->value; + } + } + + /* store attribute in cache (also negatives are kept in cache) */ + dbg("new uncached attribute '%s'", path_full); + attr = malloc(sizeof(struct sysfs_attr)); + if (attr == NULL) + return NULL; + memset(attr, 0x00, sizeof(struct sysfs_attr)); + strlcpy(attr->path, path, sizeof(attr->path)); + dbg("add to cache '%s'", path_full); + list_add(&attr->node, &attr_list); + + if (lstat(path_full, &statbuf) != 0) { + dbg("stat '%s' failed: %s", path_full, strerror(errno)); + goto out; + } + + if (S_ISLNK(statbuf.st_mode)) { + /* links return the last element of the target path */ + char link_target[PATH_SIZE]; + int len; + const char *pos; + + len = readlink(path_full, link_target, sizeof(link_target)); + if (len > 0) { + link_target[len] = '\0'; + pos = strrchr(link_target, '/'); + if (pos != NULL) { + dbg("cache '%s' with link value '%s'", path_full, pos+1); + strlcpy(attr->value_local, &pos[1], sizeof(attr->value_local)); + attr->value = attr->value_local; + } + } + goto out; + } + + /* skip directories */ + if (S_ISDIR(statbuf.st_mode)) + goto out; + + /* skip non-readable files */ + if ((statbuf.st_mode & S_IRUSR) == 0) + goto out; + + /* read attribute value */ + fd = open(path_full, O_RDONLY); + if (fd < 0) { + dbg("attribute '%s' does not exist", path_full); + goto out; + } + size = read(fd, value, sizeof(value)); + close(fd); + if (size < 0) + goto out; + if (size == sizeof(value)) + goto out; + + /* got a valid value, store and return it */ + value[size] = '\0'; + remove_trailing_chars(value, '\n'); + dbg("cache '%s' with attribute value '%s'", path_full, value); + strlcpy(attr->value_local, value, sizeof(attr->value_local)); + attr->value = attr->value_local; + +out: + return attr->value; +} |