pdc_stable.c

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/* 
 *    Interfaces to retrieve and set PDC Stable options (firmware)
 *
 *    Copyright (C) 2005-2006 Thibaut VARENE <[email protected]>
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License, version 2, as
 *    published by the Free Software Foundation.
 *
 *    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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *
 *    DEV NOTE: the PDC Procedures reference states that:
 *    "A minimum of 96 bytes of Stable Storage is required. Providing more than
 *    96 bytes of Stable Storage is optional [...]. Failure to provide the
 *    optional locations from 96 to 192 results in the loss of certain
 *    functionality during boot."
 *
 *    Since locations between 96 and 192 are the various paths, most (if not
 *    all) PA-RISC machines should have them. Anyway, for safety reasons, the
 *    following code can deal with just 96 bytes of Stable Storage, and all
 *    sizes between 96 and 192 bytes (provided they are multiple of struct
 *    device_path size, eg: 128, 160 and 192) to provide full information.
 *    One last word: there's one path we can always count on: the primary path.
 *    Anything above 224 bytes is used for 'osdep2' OS-dependent storage area.
 *
 *    The first OS-dependent area should always be available. Obviously, this is
 *    not true for the other one. Also bear in mind that reading/writing from/to
 *    osdep2 is much more expensive than from/to osdep1.
 *    NOTE: We do not handle the 2 bytes OS-dep area at 0x5D, nor the first
 *    2 bytes of storage available right after OSID. That's a total of 4 bytes
 *    sacrificed: -ETOOLAZY :P
 *
 *    The current policy wrt file permissions is:
 *  - write: root only
 *  - read: (reading triggers PDC calls) ? root only : everyone
 *    The rationale is that PDC calls could hog (DoS) the machine.
 *
 *  TODO:
 *  - timer/fastsize write calls
 */

#undef PDCS_DEBUG
#ifdef PDCS_DEBUG
#define DPRINTK(fmt, args...)   printk(KERN_DEBUG fmt, ## args)
#else
#define DPRINTK(fmt, args...)
#endif

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/capability.h>
#include <linux/ctype.h>
#include <linux/sysfs.h>
#include <linux/kobject.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/spinlock.h>

#include <asm/pdc.h>
#include <asm/page.h>
#include <asm/uaccess.h>
#include <asm/hardware.h>

#define PDCS_VERSION    "0.30"
#define PDCS_PREFIX "PDC Stable Storage"

#define PDCS_ADDR_PPRI  0x00
#define PDCS_ADDR_OSID  0x40
#define PDCS_ADDR_OSD1  0x48
#define PDCS_ADDR_DIAG  0x58
#define PDCS_ADDR_FSIZ  0x5C
#define PDCS_ADDR_PCON  0x60
#define PDCS_ADDR_PALT  0x80
#define PDCS_ADDR_PKBD  0xA0
#define PDCS_ADDR_OSD2  0xE0

MODULE_AUTHOR("Thibaut VARENE <[email protected]>");
MODULE_DESCRIPTION("sysfs interface to HP PDC Stable Storage data");
MODULE_LICENSE("GPL");
MODULE_VERSION(PDCS_VERSION);

/* holds Stable Storage size. Initialized once and for all, no lock needed */
static unsigned long pdcs_size __read_mostly;

/* holds OS ID. Initialized once and for all, hopefully to 0x0006 */
static u16 pdcs_osid __read_mostly;

/* This struct defines what we need to deal with a parisc pdc path entry */
struct pdcspath_entry {
    rwlock_t rw_lock;       /* to protect path entry access */
    short ready;            /* entry record is valid if != 0 */
    unsigned long addr;     /* entry address in stable storage */
    char *name;         /* entry name */
    struct device_path devpath; /* device path in parisc representation */
    struct device *dev;     /* corresponding device */
    struct kobject kobj;
};

struct pdcspath_attribute {
    struct attribute attr;
    ssize_t (*show)(struct pdcspath_entry *entry, char *buf);
    ssize_t (*store)(struct pdcspath_entry *entry, const char *buf, size_t count);
};

#define PDCSPATH_ENTRY(_addr, _name) \
struct pdcspath_entry pdcspath_entry_##_name = { \
    .ready = 0, \
    .addr = _addr, \
    .name = __stringify(_name), \
};

#define PDCS_ATTR(_name, _mode, _show, _store) \
struct kobj_attribute pdcs_attr_##_name = { \
    .attr = {.name = __stringify(_name), .mode = _mode}, \
    .show = _show, \
    .store = _store, \
};

#define PATHS_ATTR(_name, _mode, _show, _store) \
struct pdcspath_attribute paths_attr_##_name = { \
    .attr = {.name = __stringify(_name), .mode = _mode}, \
    .show = _show, \
    .store = _store, \
};

#define to_pdcspath_attribute(_attr) container_of(_attr, struct pdcspath_attribute, attr)
#define to_pdcspath_entry(obj)  container_of(obj, struct pdcspath_entry, kobj)

static int
pdcspath_fetch(struct pdcspath_entry *entry)
{
    struct device_path *devpath;

    if (!entry)
        return -EINVAL;

    devpath = &entry->devpath;
    
    DPRINTK("%s: fetch: 0x%p, 0x%p, addr: 0x%lx\n", __func__,
            entry, devpath, entry->addr);

    /* addr, devpath and count must be word aligned */
    if (pdc_stable_read(entry->addr, devpath, sizeof(*devpath)) != PDC_OK)
        return -EIO;
        
    /* Find the matching device.
       NOTE: hardware_path overlays with device_path, so the nice cast can
       be used */
    entry->dev = hwpath_to_device((struct hardware_path *)devpath);

    entry->ready = 1;
    
    DPRINTK("%s: device: 0x%p\n", __func__, entry->dev);
    
    return 0;
}

static void
pdcspath_store(struct pdcspath_entry *entry)
{
    struct device_path *devpath;

    BUG_ON(!entry);

    devpath = &entry->devpath;
    
    /* We expect the caller to set the ready flag to 0 if the hardware
       path struct provided is invalid, so that we know we have to fill it.
       First case, we don't have a preset hwpath... */
    if (!entry->ready) {
        /* ...but we have a device, map it */
        BUG_ON(!entry->dev);
        device_to_hwpath(entry->dev, (struct hardware_path *)devpath);
    }
    /* else, we expect the provided hwpath to be valid. */
    
    DPRINTK("%s: store: 0x%p, 0x%p, addr: 0x%lx\n", __func__,
            entry, devpath, entry->addr);

    /* addr, devpath and count must be word aligned */
    if (pdc_stable_write(entry->addr, devpath, sizeof(*devpath)) != PDC_OK) {
        printk(KERN_ERR "%s: an error occurred when writing to PDC.\n"
                "It is likely that the Stable Storage data has been corrupted.\n"
                "Please check it carefully upon next reboot.\n", __func__);
        WARN_ON(1);
    }
        
    /* kobject is already registered */
    entry->ready = 2;
    
    DPRINTK("%s: device: 0x%p\n", __func__, entry->dev);
}

static ssize_t
pdcspath_hwpath_read(struct pdcspath_entry *entry, char *buf)
{
    char *out = buf;
    struct device_path *devpath;
    short i;

    if (!entry || !buf)
        return -EINVAL;

    read_lock(&entry->rw_lock);
    devpath = &entry->devpath;
    i = entry->ready;
    read_unlock(&entry->rw_lock);

    if (!i) /* entry is not ready */
        return -ENODATA;
    
    for (i = 0; i < 6; i++) {
        if (devpath->bc[i] >= 128)
            continue;
        out += sprintf(out, "%u/", (unsigned char)devpath->bc[i]);
    }
    out += sprintf(out, "%u\n", (unsigned char)devpath->mod);
    
    return out - buf;
}

static ssize_t
pdcspath_hwpath_write(struct pdcspath_entry *entry, const char *buf, size_t count)
{
    struct hardware_path hwpath;
    unsigned short i;
    char in[count+1], *temp;
    struct device *dev;
    int ret;

    if (!entry || !buf || !count)
        return -EINVAL;

    /* We'll use a local copy of buf */
    memset(in, 0, count+1);
    strncpy(in, buf, count);
    
    /* Let's clean up the target. 0xff is a blank pattern */
    memset(&hwpath, 0xff, sizeof(hwpath));
    
    /* First, pick the mod field (the last one of the input string) */
    if (!(temp = strrchr(in, '/')))
        return -EINVAL;
            
    hwpath.mod = simple_strtoul(temp+1, NULL, 10);
    in[temp-in] = '\0'; /* truncate the remaining string. just precaution */
    DPRINTK("%s: mod: %d\n", __func__, hwpath.mod);
    
    /* Then, loop for each delimiter, making sure we don't have too many.
       we write the bc fields in a down-top way. No matter what, we stop
       before writing the last field. If there are too many fields anyway,
       then the user is a moron and it'll be caught up later when we'll
       check the consistency of the given hwpath. */
    for (i=5; ((temp = strrchr(in, '/'))) && (temp-in > 0) && (likely(i)); i--) {
        hwpath.bc[i] = simple_strtoul(temp+1, NULL, 10);
        in[temp-in] = '\0';
        DPRINTK("%s: bc[%d]: %d\n", __func__, i, hwpath.bc[i]);
    }
    
    /* Store the final field */     
    hwpath.bc[i] = simple_strtoul(in, NULL, 10);
    DPRINTK("%s: bc[%d]: %d\n", __func__, i, hwpath.bc[i]);
    
    /* Now we check that the user isn't trying to lure us */
    if (!(dev = hwpath_to_device((struct hardware_path *)&hwpath))) {
        printk(KERN_WARNING "%s: attempt to set invalid \"%s\" "
            "hardware path: %s\n", __func__, entry->name, buf);
        return -EINVAL;
    }
    
    /* So far so good, let's get in deep */
    write_lock(&entry->rw_lock);
    entry->ready = 0;
    entry->dev = dev;
    
    /* Now, dive in. Write back to the hardware */
    pdcspath_store(entry);
    
    /* Update the symlink to the real device */
    sysfs_remove_link(&entry->kobj, "device");
    ret = sysfs_create_link(&entry->kobj, &entry->dev->kobj, "device");
    WARN_ON(ret);

    write_unlock(&entry->rw_lock);
    
    printk(KERN_INFO PDCS_PREFIX ": changed \"%s\" path to \"%s\"\n",
        entry->name, buf);
    
    return count;
}

static ssize_t
pdcspath_layer_read(struct pdcspath_entry *entry, char *buf)
{
    char *out = buf;
    struct device_path *devpath;
    short i;

    if (!entry || !buf)
        return -EINVAL;
    
    read_lock(&entry->rw_lock);
    devpath = &entry->devpath;
    i = entry->ready;
    read_unlock(&entry->rw_lock);

    if (!i) /* entry is not ready */
        return -ENODATA;
    
    for (i = 0; i < 6 && devpath->layers[i]; i++)
        out += sprintf(out, "%u ", devpath->layers[i]);

    out += sprintf(out, "\n");
    
    return out - buf;
}

static ssize_t
pdcspath_layer_write(struct pdcspath_entry *entry, const char *buf, size_t count)
{
    unsigned int layers[6]; /* device-specific info (ctlr#, unit#, ...) */
    unsigned short i;
    char in[count+1], *temp;

    if (!entry || !buf || !count)
        return -EINVAL;

    /* We'll use a local copy of buf */
    memset(in, 0, count+1);
    strncpy(in, buf, count);
    
    /* Let's clean up the target. 0 is a blank pattern */
    memset(&layers, 0, sizeof(layers));
    
    /* First, pick the first layer */
    if (unlikely(!isdigit(*in)))
        return -EINVAL;
    layers[0] = simple_strtoul(in, NULL, 10);
    DPRINTK("%s: layer[0]: %d\n", __func__, layers[0]);
    
    temp = in;
    for (i=1; ((temp = strchr(temp, '.'))) && (likely(i<6)); i++) {
        if (unlikely(!isdigit(*(++temp))))
            return -EINVAL;
        layers[i] = simple_strtoul(temp, NULL, 10);
        DPRINTK("%s: layer[%d]: %d\n", __func__, i, layers[i]);
    }
        
    /* So far so good, let's get in deep */
    write_lock(&entry->rw_lock);
    
    /* First, overwrite the current layers with the new ones, not touching
       the hardware path. */
    memcpy(&entry->devpath.layers, &layers, sizeof(layers));
    
    /* Now, dive in. Write back to the hardware */
    pdcspath_store(entry);
    write_unlock(&entry->rw_lock);
    
    printk(KERN_INFO PDCS_PREFIX ": changed \"%s\" layers to \"%s\"\n",
        entry->name, buf);
    
    return count;
}

static ssize_t
pdcspath_attr_show(struct kobject *kobj, struct attribute *attr, char *buf)
{
    struct pdcspath_entry *entry = to_pdcspath_entry(kobj);
    struct pdcspath_attribute *pdcs_attr = to_pdcspath_attribute(attr);
    ssize_t ret = 0;

    if (pdcs_attr->show)
        ret = pdcs_attr->show(entry, buf);

    return ret;
}

static ssize_t
pdcspath_attr_store(struct kobject *kobj, struct attribute *attr,
            const char *buf, size_t count)
{
    struct pdcspath_entry *entry = to_pdcspath_entry(kobj);
    struct pdcspath_attribute *pdcs_attr = to_pdcspath_attribute(attr);
    ssize_t ret = 0;

    if (!capable(CAP_SYS_ADMIN))
        return -EACCES;

    if (pdcs_attr->store)
        ret = pdcs_attr->store(entry, buf, count);

    return ret;
}

static const struct sysfs_ops pdcspath_attr_ops = {
    .show = pdcspath_attr_show,
    .store = pdcspath_attr_store,
};

/* These are the two attributes of any PDC path. */
static PATHS_ATTR(hwpath, 0644, pdcspath_hwpath_read, pdcspath_hwpath_write);
static PATHS_ATTR(layer, 0644, pdcspath_layer_read, pdcspath_layer_write);

static struct attribute *paths_subsys_attrs[] = {
    &paths_attr_hwpath.attr,
    &paths_attr_layer.attr,
    NULL,
};

/* Specific kobject type for our PDC paths */
static struct kobj_type ktype_pdcspath = {
    .sysfs_ops = &pdcspath_attr_ops,
    .default_attrs = paths_subsys_attrs,
};

/* We hard define the 4 types of path we expect to find */
static PDCSPATH_ENTRY(PDCS_ADDR_PPRI, primary);
static PDCSPATH_ENTRY(PDCS_ADDR_PCON, console);
static PDCSPATH_ENTRY(PDCS_ADDR_PALT, alternative);
static PDCSPATH_ENTRY(PDCS_ADDR_PKBD, keyboard);

/* An array containing all PDC paths we will deal with */
static struct pdcspath_entry *pdcspath_entries[] = {
    &pdcspath_entry_primary,
    &pdcspath_entry_alternative,
    &pdcspath_entry_console,
    &pdcspath_entry_keyboard,
    NULL,
};


/* For more insight of what's going on here, refer to PDC Procedures doc,
 * Section PDC_STABLE */

static ssize_t pdcs_size_read(struct kobject *kobj,
                  struct kobj_attribute *attr,
                  char *buf)
{
    char *out = buf;

    if (!buf)
        return -EINVAL;

    /* show the size of the stable storage */
    out += sprintf(out, "%ld\n", pdcs_size);

    return out - buf;
}

static ssize_t pdcs_auto_read(struct kobject *kobj,
                  struct kobj_attribute *attr,
                  char *buf, int knob)
{
    char *out = buf;
    struct pdcspath_entry *pathentry;

    if (!buf)
        return -EINVAL;

    /* Current flags are stored in primary boot path entry */
    pathentry = &pdcspath_entry_primary;

    read_lock(&pathentry->rw_lock);
    out += sprintf(out, "%s\n", (pathentry->devpath.flags & knob) ?
                    "On" : "Off");
    read_unlock(&pathentry->rw_lock);

    return out - buf;
}

static ssize_t pdcs_autoboot_read(struct kobject *kobj,
                  struct kobj_attribute *attr, char *buf)
{
    return pdcs_auto_read(kobj, attr, buf, PF_AUTOBOOT);
}

static ssize_t pdcs_autosearch_read(struct kobject *kobj,
                    struct kobj_attribute *attr, char *buf)
{
    return pdcs_auto_read(kobj, attr, buf, PF_AUTOSEARCH);
}

static ssize_t pdcs_timer_read(struct kobject *kobj,
                   struct kobj_attribute *attr, char *buf)
{
    char *out = buf;
    struct pdcspath_entry *pathentry;

    if (!buf)
        return -EINVAL;

    /* Current flags are stored in primary boot path entry */
    pathentry = &pdcspath_entry_primary;

    /* print the timer value in seconds */
    read_lock(&pathentry->rw_lock);
    out += sprintf(out, "%u\n", (pathentry->devpath.flags & PF_TIMER) ?
                (1 << (pathentry->devpath.flags & PF_TIMER)) : 0);
    read_unlock(&pathentry->rw_lock);

    return out - buf;
}

static ssize_t pdcs_osid_read(struct kobject *kobj,
                  struct kobj_attribute *attr, char *buf)
{
    char *out = buf;

    if (!buf)
        return -EINVAL;

    out += sprintf(out, "%s dependent data (0x%.4x)\n",
        os_id_to_string(pdcs_osid), pdcs_osid);

    return out - buf;
}

static ssize_t pdcs_osdep1_read(struct kobject *kobj,
                struct kobj_attribute *attr, char *buf)
{
    char *out = buf;
    u32 result[4];

    if (!buf)
        return -EINVAL;

    if (pdc_stable_read(PDCS_ADDR_OSD1, &result, sizeof(result)) != PDC_OK)
        return -EIO;

    out += sprintf(out, "0x%.8x\n", result[0]);
    out += sprintf(out, "0x%.8x\n", result[1]);
    out += sprintf(out, "0x%.8x\n", result[2]);
    out += sprintf(out, "0x%.8x\n", result[3]);

    return out - buf;
}

static ssize_t pdcs_diagnostic_read(struct kobject *kobj,
                    struct kobj_attribute *attr, char *buf)
{
    char *out = buf;
    u32 result;

    if (!buf)
        return -EINVAL;

    /* get diagnostic */
    if (pdc_stable_read(PDCS_ADDR_DIAG, &result, sizeof(result)) != PDC_OK)
        return -EIO;

    out += sprintf(out, "0x%.4x\n", (result >> 16));

    return out - buf;
}

static ssize_t pdcs_fastsize_read(struct kobject *kobj,
                  struct kobj_attribute *attr, char *buf)
{
    char *out = buf;
    u32 result;

    if (!buf)
        return -EINVAL;

    /* get fast-size */
    if (pdc_stable_read(PDCS_ADDR_FSIZ, &result, sizeof(result)) != PDC_OK)
        return -EIO;

    if ((result & 0x0F) < 0x0E)
        out += sprintf(out, "%d kB", (1<<(result & 0x0F))*256);
    else
        out += sprintf(out, "All");
    out += sprintf(out, "\n");
    
    return out - buf;
}

static ssize_t pdcs_osdep2_read(struct kobject *kobj,
                struct kobj_attribute *attr, char *buf)
{
    char *out = buf;
    unsigned long size;
    unsigned short i;
    u32 result;

    if (unlikely(pdcs_size <= 224))
        return -ENODATA;

    size = pdcs_size - 224;

    if (!buf)
        return -EINVAL;

    for (i=0; i<size; i+=4) {
        if (unlikely(pdc_stable_read(PDCS_ADDR_OSD2 + i, &result,
                    sizeof(result)) != PDC_OK))
            return -EIO;
        out += sprintf(out, "0x%.8x\n", result);
    }

    return out - buf;
}

static ssize_t pdcs_auto_write(struct kobject *kobj,
                   struct kobj_attribute *attr, const char *buf,
                   size_t count, int knob)
{
    struct pdcspath_entry *pathentry;
    unsigned char flags;
    char in[count+1], *temp;
    char c;

    if (!capable(CAP_SYS_ADMIN))
        return -EACCES;

    if (!buf || !count)
        return -EINVAL;

    /* We'll use a local copy of buf */
    memset(in, 0, count+1);
    strncpy(in, buf, count);

    /* Current flags are stored in primary boot path entry */
    pathentry = &pdcspath_entry_primary;
    
    /* Be nice to the existing flag record */
    read_lock(&pathentry->rw_lock);
    flags = pathentry->devpath.flags;
    read_unlock(&pathentry->rw_lock);
    
    DPRINTK("%s: flags before: 0x%X\n", __func__, flags);

    temp = skip_spaces(in);

    c = *temp++ - '0';
    if ((c != 0) && (c != 1))
        goto parse_error;
    if (c == 0)
        flags &= ~knob;
    else
        flags |= knob;
    
    DPRINTK("%s: flags after: 0x%X\n", __func__, flags);
        
    /* So far so good, let's get in deep */
    write_lock(&pathentry->rw_lock);
    
    /* Change the path entry flags first */
    pathentry->devpath.flags = flags;
        
    /* Now, dive in. Write back to the hardware */
    pdcspath_store(pathentry);
    write_unlock(&pathentry->rw_lock);
    
    printk(KERN_INFO PDCS_PREFIX ": changed \"%s\" to \"%s\"\n",
        (knob & PF_AUTOBOOT) ? "autoboot" : "autosearch",
        (flags & knob) ? "On" : "Off");
    
    return count;

parse_error:
    printk(KERN_WARNING "%s: Parse error: expect \"n\" (n == 0 or 1)\n", __func__);
    return -EINVAL;
}

static ssize_t pdcs_autoboot_write(struct kobject *kobj,
                   struct kobj_attribute *attr,
                   const char *buf, size_t count)
{
    return pdcs_auto_write(kobj, attr, buf, count, PF_AUTOBOOT);
}

static ssize_t pdcs_autosearch_write(struct kobject *kobj,
                     struct kobj_attribute *attr,
                     const char *buf, size_t count)
{
    return pdcs_auto_write(kobj, attr, buf, count, PF_AUTOSEARCH);
}

static ssize_t pdcs_osdep1_write(struct kobject *kobj,
                 struct kobj_attribute *attr,
                 const char *buf, size_t count)
{
    u8 in[16];

    if (!capable(CAP_SYS_ADMIN))
        return -EACCES;

    if (!buf || !count)
        return -EINVAL;

    if (unlikely(pdcs_osid != OS_ID_LINUX))
        return -EPERM;

    if (count > 16)
        return -EMSGSIZE;

    /* We'll use a local copy of buf */
    memset(in, 0, 16);
    memcpy(in, buf, count);

    if (pdc_stable_write(PDCS_ADDR_OSD1, &in, sizeof(in)) != PDC_OK)
        return -EIO;

    return count;
}

static ssize_t pdcs_osdep2_write(struct kobject *kobj,
                 struct kobj_attribute *attr,
                 const char *buf, size_t count)
{
    unsigned long size;
    unsigned short i;
    u8 in[4];

    if (!capable(CAP_SYS_ADMIN))
        return -EACCES;

    if (!buf || !count)
        return -EINVAL;

    if (unlikely(pdcs_size <= 224))
        return -ENOSYS;

    if (unlikely(pdcs_osid != OS_ID_LINUX))
        return -EPERM;

    size = pdcs_size - 224;

    if (count > size)
        return -EMSGSIZE;

    /* We'll use a local copy of buf */

    for (i=0; i<count; i+=4) {
        memset(in, 0, 4);
        memcpy(in, buf+i, (count-i < 4) ? count-i : 4);
        if (unlikely(pdc_stable_write(PDCS_ADDR_OSD2 + i, &in,
                    sizeof(in)) != PDC_OK))
            return -EIO;
    }

    return count;
}

/* The remaining attributes. */
static PDCS_ATTR(size, 0444, pdcs_size_read, NULL);
static PDCS_ATTR(autoboot, 0644, pdcs_autoboot_read, pdcs_autoboot_write);
static PDCS_ATTR(autosearch, 0644, pdcs_autosearch_read, pdcs_autosearch_write);
static PDCS_ATTR(timer, 0444, pdcs_timer_read, NULL);
static PDCS_ATTR(osid, 0444, pdcs_osid_read, NULL);
static PDCS_ATTR(osdep1, 0600, pdcs_osdep1_read, pdcs_osdep1_write);
static PDCS_ATTR(diagnostic, 0400, pdcs_diagnostic_read, NULL);
static PDCS_ATTR(fastsize, 0400, pdcs_fastsize_read, NULL);
static PDCS_ATTR(osdep2, 0600, pdcs_osdep2_read, pdcs_osdep2_write);

static struct attribute *pdcs_subsys_attrs[] = {
    &pdcs_attr_size.attr,
    &pdcs_attr_autoboot.attr,
    &pdcs_attr_autosearch.attr,
    &pdcs_attr_timer.attr,
    &pdcs_attr_osid.attr,
    &pdcs_attr_osdep1.attr,
    &pdcs_attr_diagnostic.attr,
    &pdcs_attr_fastsize.attr,
    &pdcs_attr_osdep2.attr,
    NULL,
};

static struct attribute_group pdcs_attr_group = {
    .attrs = pdcs_subsys_attrs,
};

static struct kobject *stable_kobj;
static struct kset *paths_kset;

static inline int __init
pdcs_register_pathentries(void)
{
    unsigned short i;
    struct pdcspath_entry *entry;
    int err;
    
    /* Initialize the entries rw_lock before anything else */
    for (i = 0; (entry = pdcspath_entries[i]); i++)
        rwlock_init(&entry->rw_lock);

    for (i = 0; (entry = pdcspath_entries[i]); i++) {
        write_lock(&entry->rw_lock);
        err = pdcspath_fetch(entry);
        write_unlock(&entry->rw_lock);

        if (err < 0)
            continue;

        entry->kobj.kset = paths_kset;
        err = kobject_init_and_add(&entry->kobj, &ktype_pdcspath, NULL,
                       "%s", entry->name);
        if (err)
            return err;

        /* kobject is now registered */
        write_lock(&entry->rw_lock);
        entry->ready = 2;
        
        /* Add a nice symlink to the real device */
        if (entry->dev) {
            err = sysfs_create_link(&entry->kobj, &entry->dev->kobj, "device");
            WARN_ON(err);
        }

        write_unlock(&entry->rw_lock);
        kobject_uevent(&entry->kobj, KOBJ_ADD);
    }
    
    return 0;
}

static inline void
pdcs_unregister_pathentries(void)
{
    unsigned short i;
    struct pdcspath_entry *entry;
    
    for (i = 0; (entry = pdcspath_entries[i]); i++) {
        read_lock(&entry->rw_lock);
        if (entry->ready >= 2)
            kobject_put(&entry->kobj);
        read_unlock(&entry->rw_lock);
    }
}

/*
 * For now we register the stable subsystem with the firmware subsystem
 * and the paths subsystem with the stable subsystem
 */
static int __init
pdc_stable_init(void)
{
    int rc = 0, error = 0;
    u32 result;

    /* find the size of the stable storage */
    if (pdc_stable_get_size(&pdcs_size) != PDC_OK) 
        return -ENODEV;

    /* make sure we have enough data */
    if (pdcs_size < 96)
        return -ENODATA;

    printk(KERN_INFO PDCS_PREFIX " facility v%s\n", PDCS_VERSION);

    /* get OSID */
    if (pdc_stable_read(PDCS_ADDR_OSID, &result, sizeof(result)) != PDC_OK)
        return -EIO;

    /* the actual result is 16 bits away */
    pdcs_osid = (u16)(result >> 16);

    /* For now we'll register the directory at /sys/firmware/stable */
    stable_kobj = kobject_create_and_add("stable", firmware_kobj);
    if (!stable_kobj) {
        rc = -ENOMEM;
        goto fail_firmreg;
    }

    /* Don't forget the root entries */
    error = sysfs_create_group(stable_kobj, &pdcs_attr_group);

    /* register the paths kset as a child of the stable kset */
    paths_kset = kset_create_and_add("paths", NULL, stable_kobj);
    if (!paths_kset) {
        rc = -ENOMEM;
        goto fail_ksetreg;
    }

    /* now we create all "files" for the paths kset */
    if ((rc = pdcs_register_pathentries()))
        goto fail_pdcsreg;

    return rc;
    
fail_pdcsreg:
    pdcs_unregister_pathentries();
    kset_unregister(paths_kset);
    
fail_ksetreg:
    kobject_put(stable_kobj);
    
fail_firmreg:
    printk(KERN_INFO PDCS_PREFIX " bailing out\n");
    return rc;
}

static void __exit
pdc_stable_exit(void)
{
    pdcs_unregister_pathentries();
    kset_unregister(paths_kset);
    kobject_put(stable_kobj);
}


module_init(pdc_stable_init);
module_exit(pdc_stable_exit);