sysfs.c

/*
    sysfs.c - Part of libsensors, a library for reading Linux sensor data
    Copyright (c) 2005 Mark M. Hoffman <mhoffman@lightlink.com>
    Copyright (C) 2007-2014 Jean Delvare <jdelvare@suse.de>

    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 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.
*/

/*** This file modified by Arm on Jan 23, 2013 to improve performance by substituting calls to fread() with calls to read() and to read non-scaled values. ***/

/* this define needed for strndup() */
#define _GNU_SOURCE

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/vfs.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <limits.h>
#include <errno.h>
#include <dirent.h>
#include <fcntl.h>
#include "data.h"
#include "error.h"
#include "access.h"
#include "general.h"
#include "sysfs.h"


/****************************************************************************/

#define ATTR_MAX    128
#define SYSFS_MAGIC 0x62656572

int sensors_sysfs_no_scaling;

/*
 * Read an attribute from sysfs
 * Returns a pointer to a freshly allocated string; free it yourself.
 * If the file doesn't exist or can't be read, NULL is returned.
 */
static char *sysfs_read_attr(const char *device, const char *attr)
{
    char path[NAME_MAX];
    char buf[ATTR_MAX], *p;
    FILE *f;

    snprintf(path, NAME_MAX, "%s/%s", device, attr);

    if (!(f = fopen(path, "r")))
        return NULL;
    p = fgets(buf, ATTR_MAX, f);
    fclose(f);
    if (!p)
        return NULL;

    /* Last byte is a '\n'; chop that off */
    p = strndup(buf, strlen(buf) - 1);
    if (!p)
        sensors_fatal_error(__func__, "Out of memory");
    return p;
}

/*
 * Call an arbitrary function for each class device of the given class
 * Returns 0 on success (all calls returned 0), a positive errno for
 * local errors, or a negative error value if any call fails.
 */
static int sysfs_foreach_classdev(const char *class_name,
                   int (*func)(const char *, const char *))
{
    char path[NAME_MAX];
    int path_off, ret;
    DIR *dir;
    struct dirent *ent;

    path_off = snprintf(path, NAME_MAX, "%s/class/%s",
                sensors_sysfs_mount, class_name);
    if (!(dir = opendir(path)))
        return errno;

    ret = 0;
    while (!ret && (ent = readdir(dir))) {
        if (ent->d_name[0] == '.')  /* skip hidden entries */
            continue;

        snprintf(path + path_off, NAME_MAX - path_off, "/%s",
             ent->d_name);
        ret = func(path, ent->d_name);
    }

    closedir(dir);
    return ret;
}

/*
 * Call an arbitrary function for each device of the given bus type
 * Returns 0 on success (all calls returned 0), a positive errno for
 * local errors, or a negative error value if any call fails.
 */
static int sysfs_foreach_busdev(const char *bus_type,
                 int (*func)(const char *, const char *))
{
    char path[NAME_MAX];
    int path_off, ret;
    DIR *dir;
    struct dirent *ent;

    path_off = snprintf(path, NAME_MAX, "%s/bus/%s/devices",
                sensors_sysfs_mount, bus_type);
    if (!(dir = opendir(path)))
        return errno;

    ret = 0;
    while (!ret && (ent = readdir(dir))) {
        if (ent->d_name[0] == '.')  /* skip hidden entries */
            continue;

        snprintf(path + path_off, NAME_MAX - path_off, "/%s",
             ent->d_name);
        ret = func(path, ent->d_name);
    }

    closedir(dir);
    return ret;
}

/****************************************************************************/

char sensors_sysfs_mount[NAME_MAX];

static
int get_type_scaling(sensors_subfeature_type type)
{
    /* Multipliers for subfeatures */
    switch (type & 0xFF80) {
    case SENSORS_SUBFEATURE_IN_INPUT:
    case SENSORS_SUBFEATURE_TEMP_INPUT:
    case SENSORS_SUBFEATURE_CURR_INPUT:
    case SENSORS_SUBFEATURE_HUMIDITY_INPUT:
        return 1000;
    case SENSORS_SUBFEATURE_FAN_INPUT:
        return 1;
    case SENSORS_SUBFEATURE_POWER_AVERAGE:
    case SENSORS_SUBFEATURE_ENERGY_INPUT:
        return 1000000;
    }

    /* Multipliers for second class subfeatures
       that need their own multiplier */
    switch (type) {
    case SENSORS_SUBFEATURE_POWER_AVERAGE_INTERVAL:
    case SENSORS_SUBFEATURE_VID:
    case SENSORS_SUBFEATURE_TEMP_OFFSET:
        return 1000;
    default:
        return 1;
    }
}

static
char *get_feature_name(sensors_feature_type ftype, char *sfname)
{
    char *name, *underscore;

    switch (ftype) {
    case SENSORS_FEATURE_IN:
    case SENSORS_FEATURE_FAN:
    case SENSORS_FEATURE_TEMP:
    case SENSORS_FEATURE_POWER:
    case SENSORS_FEATURE_ENERGY:
    case SENSORS_FEATURE_CURR:
    case SENSORS_FEATURE_HUMIDITY:
    case SENSORS_FEATURE_INTRUSION:
        underscore = strchr(sfname, '_');
        name = strndup(sfname, underscore - sfname);
        if (!name)
            sensors_fatal_error(__func__, "Out of memory");

        break;
    default:
        name = strdup(sfname);
        if (!name)
            sensors_fatal_error(__func__, "Out of memory");
    }

    return name;
}

/* Static mappings for use by sensors_subfeature_get_type() */
struct subfeature_type_match
{
    const char *name;
    sensors_subfeature_type type;
};

struct feature_type_match
{
    const char *name;
    const struct subfeature_type_match *submatches;
};

static const struct subfeature_type_match temp_matches[] = {
    { "input", SENSORS_SUBFEATURE_TEMP_INPUT },
    { "max", SENSORS_SUBFEATURE_TEMP_MAX },
    { "max_hyst", SENSORS_SUBFEATURE_TEMP_MAX_HYST },
    { "min", SENSORS_SUBFEATURE_TEMP_MIN },
    { "min_hyst", SENSORS_SUBFEATURE_TEMP_MIN_HYST },
    { "crit", SENSORS_SUBFEATURE_TEMP_CRIT },
    { "crit_hyst", SENSORS_SUBFEATURE_TEMP_CRIT_HYST },
    { "lcrit", SENSORS_SUBFEATURE_TEMP_LCRIT },
    { "lcrit_hyst", SENSORS_SUBFEATURE_TEMP_LCRIT_HYST },
    { "emergency", SENSORS_SUBFEATURE_TEMP_EMERGENCY },
    { "emergency_hyst", SENSORS_SUBFEATURE_TEMP_EMERGENCY_HYST },
    { "lowest", SENSORS_SUBFEATURE_TEMP_LOWEST },
    { "highest", SENSORS_SUBFEATURE_TEMP_HIGHEST },
    { "alarm", SENSORS_SUBFEATURE_TEMP_ALARM },
    { "min_alarm", SENSORS_SUBFEATURE_TEMP_MIN_ALARM },
    { "max_alarm", SENSORS_SUBFEATURE_TEMP_MAX_ALARM },
    { "crit_alarm", SENSORS_SUBFEATURE_TEMP_CRIT_ALARM },
    { "emergency_alarm", SENSORS_SUBFEATURE_TEMP_EMERGENCY_ALARM },
    { "lcrit_alarm", SENSORS_SUBFEATURE_TEMP_LCRIT_ALARM },
    { "fault", SENSORS_SUBFEATURE_TEMP_FAULT },
    { "type", SENSORS_SUBFEATURE_TEMP_TYPE },
    { "offset", SENSORS_SUBFEATURE_TEMP_OFFSET },
    { "beep", SENSORS_SUBFEATURE_TEMP_BEEP },
    { NULL, 0 }
};

static const struct subfeature_type_match in_matches[] = {
    { "input", SENSORS_SUBFEATURE_IN_INPUT },
    { "min", SENSORS_SUBFEATURE_IN_MIN },
    { "max", SENSORS_SUBFEATURE_IN_MAX },
    { "lcrit", SENSORS_SUBFEATURE_IN_LCRIT },
    { "crit", SENSORS_SUBFEATURE_IN_CRIT },
    { "average", SENSORS_SUBFEATURE_IN_AVERAGE },
    { "lowest", SENSORS_SUBFEATURE_IN_LOWEST },
    { "highest", SENSORS_SUBFEATURE_IN_HIGHEST },
    { "alarm", SENSORS_SUBFEATURE_IN_ALARM },
    { "min_alarm", SENSORS_SUBFEATURE_IN_MIN_ALARM },
    { "max_alarm", SENSORS_SUBFEATURE_IN_MAX_ALARM },
    { "lcrit_alarm", SENSORS_SUBFEATURE_IN_LCRIT_ALARM },
    { "crit_alarm", SENSORS_SUBFEATURE_IN_CRIT_ALARM },
    { "beep", SENSORS_SUBFEATURE_IN_BEEP },
    { NULL, 0 }
};

static const struct subfeature_type_match fan_matches[] = {
    { "input", SENSORS_SUBFEATURE_FAN_INPUT },
    { "min", SENSORS_SUBFEATURE_FAN_MIN },
    { "max", SENSORS_SUBFEATURE_FAN_MAX },
    { "div", SENSORS_SUBFEATURE_FAN_DIV },
    { "pulses", SENSORS_SUBFEATURE_FAN_PULSES },
    { "alarm", SENSORS_SUBFEATURE_FAN_ALARM },
    { "min_alarm", SENSORS_SUBFEATURE_FAN_MIN_ALARM },
    { "max_alarm", SENSORS_SUBFEATURE_FAN_MAX_ALARM },
    { "fault", SENSORS_SUBFEATURE_FAN_FAULT },
    { "beep", SENSORS_SUBFEATURE_FAN_BEEP },
    { NULL, 0 }
};

static const struct subfeature_type_match power_matches[] = {
    { "average", SENSORS_SUBFEATURE_POWER_AVERAGE },
    { "average_highest", SENSORS_SUBFEATURE_POWER_AVERAGE_HIGHEST },
    { "average_lowest", SENSORS_SUBFEATURE_POWER_AVERAGE_LOWEST },
    { "input", SENSORS_SUBFEATURE_POWER_INPUT },
    { "input_highest", SENSORS_SUBFEATURE_POWER_INPUT_HIGHEST },
    { "input_lowest", SENSORS_SUBFEATURE_POWER_INPUT_LOWEST },
    { "cap", SENSORS_SUBFEATURE_POWER_CAP },
    { "cap_hyst", SENSORS_SUBFEATURE_POWER_CAP_HYST },
    { "cap_alarm", SENSORS_SUBFEATURE_POWER_CAP_ALARM },
    { "alarm", SENSORS_SUBFEATURE_POWER_ALARM },
    { "max", SENSORS_SUBFEATURE_POWER_MAX },
    { "max_alarm", SENSORS_SUBFEATURE_POWER_MAX_ALARM },
    { "crit", SENSORS_SUBFEATURE_POWER_CRIT },
    { "crit_alarm", SENSORS_SUBFEATURE_POWER_CRIT_ALARM },
    { "average_interval", SENSORS_SUBFEATURE_POWER_AVERAGE_INTERVAL },
    { NULL, 0 }
};

static const struct subfeature_type_match energy_matches[] = {
    { "input", SENSORS_SUBFEATURE_ENERGY_INPUT },
    { NULL, 0 }
};

static const struct subfeature_type_match curr_matches[] = {
    { "input", SENSORS_SUBFEATURE_CURR_INPUT },
    { "min", SENSORS_SUBFEATURE_CURR_MIN },
    { "max", SENSORS_SUBFEATURE_CURR_MAX },
    { "lcrit", SENSORS_SUBFEATURE_CURR_LCRIT },
    { "crit", SENSORS_SUBFEATURE_CURR_CRIT },
    { "average", SENSORS_SUBFEATURE_CURR_AVERAGE },
    { "lowest", SENSORS_SUBFEATURE_CURR_LOWEST },
    { "highest", SENSORS_SUBFEATURE_CURR_HIGHEST },
    { "alarm", SENSORS_SUBFEATURE_CURR_ALARM },
    { "min_alarm", SENSORS_SUBFEATURE_CURR_MIN_ALARM },
    { "max_alarm", SENSORS_SUBFEATURE_CURR_MAX_ALARM },
    { "lcrit_alarm", SENSORS_SUBFEATURE_CURR_LCRIT_ALARM },
    { "crit_alarm", SENSORS_SUBFEATURE_CURR_CRIT_ALARM },
    { "beep", SENSORS_SUBFEATURE_CURR_BEEP },
    { NULL, 0 }
};

static const struct subfeature_type_match humidity_matches[] = {
    { "input", SENSORS_SUBFEATURE_HUMIDITY_INPUT },
    { NULL, 0 }
};

static const struct subfeature_type_match cpu_matches[] = {
    { "vid", SENSORS_SUBFEATURE_VID },
    { NULL, 0 }
};

static const struct subfeature_type_match intrusion_matches[] = {
    { "alarm", SENSORS_SUBFEATURE_INTRUSION_ALARM },
    { "beep", SENSORS_SUBFEATURE_INTRUSION_BEEP },
    { NULL, 0 }
};
static struct feature_type_match matches[] = {
    { "temp%d%c", temp_matches },
    { "in%d%c", in_matches },
    { "fan%d%c", fan_matches },
    { "cpu%d%c", cpu_matches },
    { "power%d%c", power_matches },
    { "curr%d%c", curr_matches },
    { "energy%d%c", energy_matches },
    { "intrusion%d%c", intrusion_matches },
    { "humidity%d%c", humidity_matches },
};

/* Return the subfeature type and channel number based on the subfeature
   name */
static
sensors_subfeature_type sensors_subfeature_get_type(const char *name, int *nr)
{
    char c;
    int i, count;
    const struct subfeature_type_match *submatches;

    /* Special case */
    if (!strcmp(name, "beep_enable")) {
        *nr = 0;
        return SENSORS_SUBFEATURE_BEEP_ENABLE;
    }

    for (i = 0; i < ARRAY_SIZE(matches); i++)
        if ((count = sscanf(name, matches[i].name, nr, &c)))
            break;

    if (i == ARRAY_SIZE(matches) || count != 2 || c != '_')
        return SENSORS_SUBFEATURE_UNKNOWN;  /* no match */

    submatches = matches[i].submatches;
    name = strchr(name + 3, '_') + 1;
    for (i = 0; submatches[i].name != NULL; i++)
        if (!strcmp(name, submatches[i].name))
            return submatches[i].type;

    return SENSORS_SUBFEATURE_UNKNOWN;
}

static int sensors_compute_max_sf(void)
{
    int i, j, max, offset;
    const struct subfeature_type_match *submatches;
    sensors_feature_type ftype;

    max = 0;
    for (i = 0; i < ARRAY_SIZE(matches); i++) {
        submatches = matches[i].submatches;
        for (j = 0; submatches[j].name != NULL; j++) {
            ftype = submatches[j].type >> 8;

            if (ftype < SENSORS_FEATURE_VID) {
                offset = submatches[j].type & 0x7F;
                if (offset >= max)
                    max = offset + 1;
            } else {
                offset = submatches[j].type & 0xFF;
                if (offset >= max * 2)
                    max = ((offset + 1) + 1) / 2;
            }
        }
    }

    return max;
}

static int sensors_get_attr_mode(const char *device, const char *attr)
{
    char path[NAME_MAX];
    struct stat st;
    int mode = 0;

    snprintf(path, NAME_MAX, "%s/%s", device, attr);
    if (!stat(path, &st)) {
        if (st.st_mode & S_IRUSR)
            mode |= SENSORS_MODE_R;
        if (st.st_mode & S_IWUSR)
            mode |= SENSORS_MODE_W;
    }
    return mode;
}

static int sensors_read_dynamic_chip(sensors_chip_features *chip,
                     const char *dev_path)
{
    int i, fnum = 0, sfnum = 0, prev_slot;
    static int max_subfeatures, feature_size;
    DIR *dir;
    struct dirent *ent;
    struct {
        int count;
        sensors_subfeature *sf;
    } all_types[SENSORS_FEATURE_MAX];
    sensors_subfeature *dyn_subfeatures;
    sensors_feature *dyn_features;
    sensors_feature_type ftype;
    sensors_subfeature_type sftype;

    if (!(dir = opendir(dev_path)))
        return -errno;

    /* Dynamically figure out the max number of subfeatures */
    if (!max_subfeatures) {
        max_subfeatures = sensors_compute_max_sf();
        feature_size = max_subfeatures * 2;
    }

    /* We use a set of large sparse tables at first (one per main
       feature type present) to store all found subfeatures, so that we
       can store them sorted and then later create a dense sorted table. */
    memset(&all_types, 0, sizeof(all_types));

    while ((ent = readdir(dir))) {
        char *name;
        int nr;

        /* Skip directories and symlinks */
        if (ent->d_type != DT_REG)
            continue;

        name = ent->d_name;

        sftype = sensors_subfeature_get_type(name, &nr);
        if (sftype == SENSORS_SUBFEATURE_UNKNOWN)
            continue;
        ftype = sftype >> 8;

        /* Adjust the channel number */
        switch (ftype) {
        case SENSORS_FEATURE_FAN:
        case SENSORS_FEATURE_TEMP:
        case SENSORS_FEATURE_POWER:
        case SENSORS_FEATURE_ENERGY:
        case SENSORS_FEATURE_CURR:
        case SENSORS_FEATURE_HUMIDITY:
            nr--;
            break;
        default:
            break;
        }

        /* Skip invalid entries. The high limit is arbitrary, we just
           don't want to allocate an insane amount of memory. */
        if (nr < 0 || nr >= 1024) {
#ifdef DEBUG
            sensors_fatal_error(__func__,
                        "Invalid channel number!");
#endif
            continue;
        }

        /* (Re-)allocate memory if needed */
        if (all_types[ftype].count < nr + 1) {
            int old_count = all_types[ftype].count;
            int step = ftype < SENSORS_FEATURE_VID ? 8 :
                   ftype < SENSORS_FEATURE_BEEP_ENABLE ? 2 : 1;

            while (all_types[ftype].count < nr + 1)
                all_types[ftype].count += step;

            all_types[ftype].sf = realloc(all_types[ftype].sf,
                        all_types[ftype].count *
                        feature_size *
                        sizeof(sensors_subfeature));
            if (!all_types[ftype].sf)
                sensors_fatal_error(__func__, "Out of memory");
            memset(all_types[ftype].sf + old_count * feature_size,
                   0, (all_types[ftype].count - old_count) *
                  feature_size * sizeof(sensors_subfeature));
        }

        /* "calculate" a place to store the subfeature in our sparse,
           sorted table */
        if (ftype < SENSORS_FEATURE_VID)
            i = nr * feature_size +
                ((sftype & 0x80) >> 7) * max_subfeatures +
                (sftype & 0x7F);
        else
            i = nr * feature_size + (sftype & 0xFF);

        if (all_types[ftype].sf[i].name) {
#ifdef DEBUG
            sensors_fatal_error(__func__, "Duplicate subfeature");
#endif
            continue;
        }

        /* fill in the subfeature members */
        all_types[ftype].sf[i].type = sftype;
        all_types[ftype].sf[i].name = strdup(name);
        if (!all_types[ftype].sf[i].name)
            sensors_fatal_error(__func__, "Out of memory");

        /* Other and misc subfeatures are never scaled */
        if (sftype < SENSORS_SUBFEATURE_VID && !(sftype & 0x80))
            all_types[ftype].sf[i].flags |= SENSORS_COMPUTE_MAPPING;
        all_types[ftype].sf[i].flags |=
                    sensors_get_attr_mode(dev_path, name);

        sfnum++;
    }
    closedir(dir);

    if (!sfnum) { /* No subfeature */
        chip->subfeature = NULL;
        goto exit_free;
    }

    /* How many main features? */
    for (ftype = 0; ftype < SENSORS_FEATURE_MAX; ftype++) {
    prev_slot = -1;
        for (i = 0; i < all_types[ftype].count * feature_size; i++) {
            if (!all_types[ftype].sf[i].name)
            continue;

            if (i / feature_size != prev_slot) {
            fnum++;
                prev_slot = i / feature_size;
            }
        }
    }

    dyn_subfeatures = calloc(sfnum, sizeof(sensors_subfeature));
    dyn_features = calloc(fnum, sizeof(sensors_feature));
    if (!dyn_subfeatures || !dyn_features)
        sensors_fatal_error(__func__, "Out of memory");

    /* Copy from the sparse array to the compact array */
    sfnum = 0;
    fnum = -1;
    for (ftype = 0; ftype < SENSORS_FEATURE_MAX; ftype++) {
    prev_slot = -1;
        for (i = 0; i < all_types[ftype].count * feature_size; i++) {
            if (!all_types[ftype].sf[i].name)
            continue;

        /* New main feature? */
            if (i / feature_size != prev_slot) {
            fnum++;
                prev_slot = i / feature_size;

                dyn_features[fnum].name =
                    get_feature_name(ftype,
                        all_types[ftype].sf[i].name);
            dyn_features[fnum].number = fnum;
            dyn_features[fnum].first_subfeature = sfnum;
            dyn_features[fnum].type = ftype;
        }

            dyn_subfeatures[sfnum] = all_types[ftype].sf[i];
        dyn_subfeatures[sfnum].number = sfnum;
        /* Back to the feature */
        dyn_subfeatures[sfnum].mapping = fnum;

        sfnum++;
    }
    }

    chip->subfeature = dyn_subfeatures;
    chip->subfeature_count = sfnum;
    chip->feature = dyn_features;
    chip->feature_count = ++fnum;

exit_free:
    for (ftype = 0; ftype < SENSORS_FEATURE_MAX; ftype++)
        free(all_types[ftype].sf);
    return 0;
}

/* returns !0 if sysfs filesystem was found, 0 otherwise */
int sensors_init_sysfs(void)
{
    struct statfs statfsbuf;

    snprintf(sensors_sysfs_mount, NAME_MAX, "%s", "/sys");
    if (statfs(sensors_sysfs_mount, &statfsbuf) < 0
     || statfsbuf.f_type != SYSFS_MAGIC)
        return 0;

    return 1;
}

/* returns: number of devices added (0 or 1) if successful, <0 otherwise */
static int sensors_read_one_sysfs_chip(const char *dev_path,
                       const char *dev_name,
                       const char *hwmon_path)
{
    int domain, bus, slot, fn, vendor, product, id;
    int err = -SENSORS_ERR_KERNEL;
    char *bus_attr;
    char bus_path[NAME_MAX];
    char linkpath[NAME_MAX];
    char subsys_path[NAME_MAX], *subsys;
    int sub_len;
    sensors_chip_features entry;

    /* ignore any device without name attribute */
    if (!(entry.chip.prefix = sysfs_read_attr(hwmon_path, "name")))
        return 0;

    entry.chip.path = strdup(hwmon_path);
    if (!entry.chip.path)
        sensors_fatal_error(__func__, "Out of memory");

    if (dev_path == NULL) {
        /* Virtual device */
        entry.chip.bus.type = SENSORS_BUS_TYPE_VIRTUAL;
        entry.chip.bus.nr = 0;
        /* For now we assume that virtual devices are unique */
        entry.chip.addr = 0;
        goto done;
    }

    /* Find bus type */
    snprintf(linkpath, NAME_MAX, "%s/subsystem", dev_path);
    sub_len = readlink(linkpath, subsys_path, NAME_MAX - 1);
    if (sub_len < 0 && errno == ENOENT) {
        /* Fallback to "bus" link for kernels <= 2.6.17 */
        snprintf(linkpath, NAME_MAX, "%s/bus", dev_path);
        sub_len = readlink(linkpath, subsys_path, NAME_MAX - 1);
    }
    if (sub_len < 0) {
        /* Older kernels (<= 2.6.11) have neither the subsystem
           symlink nor the bus symlink */
        if (errno == ENOENT)
            subsys = NULL;
        else
            goto exit_free;
    } else {
        subsys_path[sub_len] = '\0';
        subsys = strrchr(subsys_path, '/') + 1;
    }

    if ((!subsys || !strcmp(subsys, "i2c")) &&
        sscanf(dev_name, "%hd-%x", &entry.chip.bus.nr,
           &entry.chip.addr) == 2) {
        /* find out if legacy ISA or not */
        if (entry.chip.bus.nr == 9191) {
            entry.chip.bus.type = SENSORS_BUS_TYPE_ISA;
            entry.chip.bus.nr = 0;
        } else {
            entry.chip.bus.type = SENSORS_BUS_TYPE_I2C;
            snprintf(bus_path, sizeof(bus_path),
                "%s/class/i2c-adapter/i2c-%d/device",
                sensors_sysfs_mount, entry.chip.bus.nr);

            if ((bus_attr = sysfs_read_attr(bus_path, "name"))) {
                if (!strncmp(bus_attr, "ISA ", 4)) {
                    entry.chip.bus.type = SENSORS_BUS_TYPE_ISA;
                    entry.chip.bus.nr = 0;
                }

                free(bus_attr);
            }
        }
    } else
    if ((!subsys || !strcmp(subsys, "spi")) &&
        sscanf(dev_name, "spi%hd.%d", &entry.chip.bus.nr,
           &entry.chip.addr) == 2) {
        /* SPI */
        entry.chip.bus.type = SENSORS_BUS_TYPE_SPI;
    } else
    if ((!subsys || !strcmp(subsys, "pci")) &&
        sscanf(dev_name, "%x:%x:%x.%x", &domain, &bus, &slot, &fn) == 4) {
        /* PCI */
        entry.chip.addr = (domain << 16) + (bus << 8) + (slot << 3) + fn;
        entry.chip.bus.type = SENSORS_BUS_TYPE_PCI;
        entry.chip.bus.nr = 0;
    } else
    if ((!subsys || !strcmp(subsys, "platform") ||
            !strcmp(subsys, "of_platform"))) {
        /* must be new ISA (platform driver) */
        if (sscanf(dev_name, "%*[a-z0-9_].%d", &entry.chip.addr) != 1)
            entry.chip.addr = 0;
        entry.chip.bus.type = SENSORS_BUS_TYPE_ISA;
        entry.chip.bus.nr = 0;
    } else if (subsys && !strcmp(subsys, "acpi")) {
        entry.chip.bus.type = SENSORS_BUS_TYPE_ACPI;
        /* For now we assume that acpi devices are unique */
        entry.chip.bus.nr = 0;
        entry.chip.addr = 0;
    } else
    if (subsys && !strcmp(subsys, "hid") &&
        sscanf(dev_name, "%x:%x:%x.%x", &bus, &vendor, &product, &id) == 4) {
        entry.chip.bus.type = SENSORS_BUS_TYPE_HID;
        /* As of kernel 2.6.32, the hid device names don't look good */
        entry.chip.bus.nr = bus;
        entry.chip.addr = id;
    } else {
        /* Ignore unknown device */
        err = 0;
        goto exit_free;
    }

done:
    if (sensors_read_dynamic_chip(&entry, hwmon_path) < 0)
        goto exit_free;
    if (!entry.subfeature) { /* No subfeature, discard chip */
        err = 0;
        goto exit_free;
    }
    sensors_add_proc_chips(&entry);

    return 1;

exit_free:
    free(entry.chip.prefix);
    free(entry.chip.path);
    return err;
}

static int sensors_add_hwmon_device_compat(const char *path,
                       const char *dev_name)
{
    int err;

    err = sensors_read_one_sysfs_chip(path, dev_name, path);
    if (err < 0)
        return err;
    return 0;
}

/* returns 0 if successful, !0 otherwise */
static int sensors_read_sysfs_chips_compat(void)
{
    int ret;

    ret = sysfs_foreach_busdev("i2c", sensors_add_hwmon_device_compat);
    if (ret && ret != ENOENT)
        return -SENSORS_ERR_KERNEL;

    return 0;
}

static int sensors_add_hwmon_device(const char *path, const char *classdev)
{
    char linkpath[NAME_MAX];
    char device[NAME_MAX], *device_p;
    int dev_len, err;
    (void)classdev; /* hide warning */

    snprintf(linkpath, NAME_MAX, "%s/device", path);
    dev_len = readlink(linkpath, device, NAME_MAX - 1);
    if (dev_len < 0) {
        /* No device link? Treat as virtual */
        err = sensors_read_one_sysfs_chip(NULL, NULL, path);
    } else {
        device[dev_len] = '\0';
        device_p = strrchr(device, '/') + 1;

        /* The attributes we want might be those of the hwmon class
           device, or those of the device itself. */
        err = sensors_read_one_sysfs_chip(linkpath, device_p, path);
        if (err == 0)
            err = sensors_read_one_sysfs_chip(linkpath, device_p,
                              linkpath);
    }
    if (err < 0)
        return err;
    return 0;
}

/* returns 0 if successful, !0 otherwise */
int sensors_read_sysfs_chips(void)
{
    int ret;

    ret = sysfs_foreach_classdev("hwmon", sensors_add_hwmon_device);
    if (ret == ENOENT) {
        /* compatibility function for kernel 2.6.n where n <= 13 */
        return sensors_read_sysfs_chips_compat();
    }

    if (ret > 0)
        ret = -SENSORS_ERR_KERNEL;
    return ret;
}

/* returns 0 if successful, !0 otherwise */
static int sensors_add_i2c_bus(const char *path, const char *classdev)
{
    sensors_bus entry;

    if (sscanf(classdev, "i2c-%hd", &entry.bus.nr) != 1 ||
        entry.bus.nr == 9191) /* legacy ISA */
        return 0;
    entry.bus.type = SENSORS_BUS_TYPE_I2C;

    /* Get the adapter name from the classdev "name" attribute
     * (Linux 2.6.20 and later). If it fails, fall back to
     * the device "name" attribute (for older kernels). */
    entry.adapter = sysfs_read_attr(path, "name");
    if (!entry.adapter)
        entry.adapter = sysfs_read_attr(path, "device/name");
    if (entry.adapter)
        sensors_add_proc_bus(&entry);

    return 0;
}

/* returns 0 if successful, !0 otherwise */
int sensors_read_sysfs_bus(void)
{
    int ret;

    ret = sysfs_foreach_classdev("i2c-adapter", sensors_add_i2c_bus);
    if (ret == ENOENT)
        ret = sysfs_foreach_busdev("i2c", sensors_add_i2c_bus);
    if (ret && ret != ENOENT)
        return -SENSORS_ERR_KERNEL;

    return 0;
}

int sensors_read_sysfs_attr(const sensors_chip_name *name,
                const sensors_subfeature *subfeature,
                double *value)
{
    char n[NAME_MAX];
    int f;

    snprintf(n, NAME_MAX, "%s/%s", name->path, subfeature->name);
    if ((f = open(n, O_RDONLY)) != -1) {
        int res, err = 0;
        char buf[512];
        int count;

        errno = 0;
        if ((count = read(f, buf, sizeof(buf) - 1)) == -1) {
            if (errno == EIO)
                err = -SENSORS_ERR_IO;
            else
                err = -SENSORS_ERR_ACCESS_R;
        } else {
            buf[count] = '\0';
            errno = 0;
            res = sscanf(buf, "%lf", value);
            if (res == EOF && errno == EIO)
                err = -SENSORS_ERR_IO;
            else if (res != 1)
                err = -SENSORS_ERR_ACCESS_R;
        }
        res = close(f);
        if (err)
            return err;

        if (res != 0) {
            if (errno == EIO)
                return -SENSORS_ERR_IO;
            else
                return -SENSORS_ERR_ACCESS_R;
        }
        if (!sensors_sysfs_no_scaling)
            *value /= get_type_scaling(subfeature->type);
    } else
        return -SENSORS_ERR_KERNEL;

    return 0;
}

int sensors_write_sysfs_attr(const sensors_chip_name *name,
                 const sensors_subfeature *subfeature,
                 double value)
{
    char n[NAME_MAX];
    FILE *f;

    snprintf(n, NAME_MAX, "%s/%s", name->path, subfeature->name);
    if ((f = fopen(n, "w"))) {
        int res, err = 0;

        if (!sensors_sysfs_no_scaling)
            value *= get_type_scaling(subfeature->type);
        res = fprintf(f, "%d", (int) value);
        if (res == -EIO)
            err = -SENSORS_ERR_IO;
        else if (res < 0)
            err = -SENSORS_ERR_ACCESS_W;
        res = fclose(f);
        if (err)
            return err;

        if (res == EOF) {
            if (errno == EIO)
                return -SENSORS_ERR_IO;
            else
                return -SENSORS_ERR_ACCESS_W;
        }
    } else
        return -SENSORS_ERR_KERNEL;

    return 0;
}