// SPDX-License-Identifier: GPL-2.0-only

  /* 
   *    Interfaces to retrieve and set PDC Stable options (firmware)
   *

   *    Copyright (C) 2005-2006 Thibaut VARENE <varenet@parisc-linux.org>

   *

   *    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 <linux/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 <varenet@parisc-linux.org>");
  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)
  
  /**
   * pdcspath_fetch - This function populates the path entry structs.
   * @entry: A pointer to an allocated pdcspath_entry.
   * 
   * The general idea is that you don't read from the Stable Storage every time

   * you access the files provided by the facilities. We store a copy of the

   * content of the stable storage WRT various paths in these structs. We read
   * these structs when reading the files, and we will write to these structs when
   * writing to the files, and only then write them back to the Stable Storage.

   *
   * This function expects to be called with @entry->rw_lock write-hold.

   */
  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
  ", __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
  ", __func__, entry->dev);
  	
  	return 0;
  }
  
  /**
   * pdcspath_store - This function writes a path to stable storage.
   * @entry: A pointer to an allocated pdcspath_entry.
   * 
   * It can be used in two ways: either by passing it a preset devpath struct
   * containing an already computed hardware path, or by passing it a device
   * pointer, from which it'll find out the corresponding hardware path.
   * For now we do not handle the case where there's an error in writing to the
   * Stable Storage area, so you'd better not mess up the data :P

   *
   * This function expects to be called with @entry->rw_lock write-hold.

   */

  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
  ", __func__,
  			entry, devpath, entry->addr);
  
  	/* addr, devpath and count must be word aligned */

  	if (pdc_stable_write(entry->addr, devpath, sizeof(*devpath)) != PDC_OK)
  		WARN(1, KERN_ERR "%s: an error occurred when writing to PDC.
  "

  				"It is likely that the Stable Storage data has been corrupted.
  "
  				"Please check it carefully upon next reboot.
  ", __func__);

  	/* kobject is already registered */
  	entry->ready = 2;

  	
  	DPRINTK("%s: device: 0x%p
  ", __func__, entry->dev);

  }
  
  /**
   * pdcspath_hwpath_read - This function handles hardware path pretty printing.
   * @entry: An allocated and populated pdscpath_entry struct.
   * @buf: The output buffer to write to.
   * 
   * We will call this function to format the output of the hwpath attribute file.
   */
  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
  ", (unsigned char)devpath->mod);
  	
  	return out - buf;
  }
  
  /**
   * pdcspath_hwpath_write - This function handles hardware path modifying.
   * @entry: An allocated and populated pdscpath_entry struct.
   * @buf: The input buffer to read from.
   * @count: The number of bytes to be read.
   * 
   * We will call this function to change the current hardware path.
   * Hardware paths are to be given '/'-delimited, without brackets.

   * We make sure that the provided path actually maps to an existing

   * device, BUT nothing would prevent some foolish user to set the path to some
   * PCI bridge or even a CPU...
   * A better work around would be to make sure we are at the end of a device tree
   * for instance, but it would be IMHO beyond the simple scope of that driver.
   * The aim is to provide a facility. Data correctness is left to userland.
   */
  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[64], *temp;

  	struct device *dev;

  	int ret;

  
  	if (!entry || !buf || !count)
  		return -EINVAL;
  
  	/* We'll use a local copy of buf */

  	count = min_t(size_t, count, sizeof(in)-1);

  	strncpy(in, buf, count);

  	in[count] = '\0';

  	
  	/* 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
  ", __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
  ", __func__, i, hwpath.bc[i]);
  	}
  	
  	/* Store the final field */		
  	hwpath.bc[i] = simple_strtoul(in, NULL, 10);
  	DPRINTK("%s: bc[%d]: %d
  ", __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
  ", __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");

  	write_unlock(&entry->rw_lock);

  	ret = sysfs_create_link(&entry->kobj, &entry->dev->kobj, "device");
  	WARN_ON(ret);

  	printk(KERN_INFO PDCS_PREFIX ": changed \"%s\" path to \"%s\"
  ",

  		entry->name, buf);
  	
  	return count;
  }
  
  /**
   * pdcspath_layer_read - Extended layer (eg. SCSI ids) pretty printing.
   * @entry: An allocated and populated pdscpath_entry struct.
   * @buf: The output buffer to write to.
   * 
   * We will call this function to format the output of the layer attribute file.
   */
  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, "
  ");
  	
  	return out - buf;
  }
  
  /**
   * pdcspath_layer_write - This function handles extended layer modifying.
   * @entry: An allocated and populated pdscpath_entry struct.
   * @buf: The input buffer to read from.
   * @count: The number of bytes to be read.
   * 
   * We will call this function to change the current layer value.
   * Layers are to be given '.'-delimited, without brackets.
   * XXX beware we are far less checky WRT input data provided than for hwpath.
   * Potential harm can be done, since there's no way to check the validity of
   * the layer fields.
   */
  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[64], *temp;

  
  	if (!entry || !buf || !count)
  		return -EINVAL;
  
  	/* We'll use a local copy of buf */

  	count = min_t(size_t, count, sizeof(in)-1);

  	strncpy(in, buf, count);

  	in[count] = '\0';

  	
  	/* 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
  ", __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
  ", __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\"
  ",

  		entry->name, buf);
  	
  	return count;
  }
  
  /**
   * pdcspath_attr_show - Generic read function call wrapper.
   * @kobj: The kobject to get info from.
   * @attr: The attribute looked upon.
   * @buf: The output buffer.
   */
  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;
  }
  
  /**
   * pdcspath_attr_store - Generic write function call wrapper.
   * @kobj: The kobject to write info to.
   * @attr: The attribute to be modified.
   * @buf: The input buffer.
   * @count: The size of the buffer.
   */
  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 */

  /**

   * pdcs_size_read - Stable Storage size output.

   * @buf: The output buffer to write to.

   */

  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
  ", pdcs_size);

  	return out - buf;
  }
  
  /**
   * pdcs_auto_read - Stable Storage autoboot/search flag output.

   * @buf: The output buffer to write to.
   * @knob: The PF_AUTOBOOT or PF_AUTOSEARCH flag
   */

  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
  ", (pathentry->devpath.flags & knob) ?
  					"On" : "Off");
  	read_unlock(&pathentry->rw_lock);
  
  	return out - buf;
  }
  
  /**
   * pdcs_autoboot_read - Stable Storage autoboot flag output.

   * @buf: The output buffer to write to.
   */

  static ssize_t pdcs_autoboot_read(struct kobject *kobj,
  				  struct kobj_attribute *attr, char *buf)

  {

  	return pdcs_auto_read(kobj, attr, buf, PF_AUTOBOOT);

  }
  
  /**
   * pdcs_autosearch_read - Stable Storage autoboot flag output.

   * @buf: The output buffer to write to.
   */

  static ssize_t pdcs_autosearch_read(struct kobject *kobj,
  				    struct kobj_attribute *attr, char *buf)

  {

  	return pdcs_auto_read(kobj, attr, buf, PF_AUTOSEARCH);

  }
  
  /**
   * pdcs_timer_read - Stable Storage timer count output (in seconds).

   * @buf: The output buffer to write to.
   *
   * The value of the timer field correponds to a number of seconds in powers of 2.
   */

  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
  ", (pathentry->devpath.flags & PF_TIMER) ?
  				(1 << (pathentry->devpath.flags & PF_TIMER)) : 0);
  	read_unlock(&pathentry->rw_lock);
  
  	return out - buf;
  }
  
  /**
   * pdcs_osid_read - Stable Storage OS ID register output.

   * @buf: The output buffer to write to.
   */

  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)
  ",
  		os_id_to_string(pdcs_osid), pdcs_osid);

  
  	return out - buf;
  }
  
  /**
   * pdcs_osdep1_read - Stable Storage OS-Dependent data area 1 output.

   * @buf: The output buffer to write to.
   *
   * This can hold 16 bytes of OS-Dependent data.
   */

  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
  ", result[0]);
  	out += sprintf(out, "0x%.8x
  ", result[1]);
  	out += sprintf(out, "0x%.8x
  ", result[2]);
  	out += sprintf(out, "0x%.8x
  ", result[3]);
  
  	return out - buf;
  }
  
  /**
   * pdcs_diagnostic_read - Stable Storage Diagnostic register output.

   * @buf: The output buffer to write to.
   *
   * I have NFC how to interpret the content of that register ;-).
   */

  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
  ", (result >> 16));

  
  	return out - buf;
  }
  
  /**
   * pdcs_fastsize_read - Stable Storage FastSize register output.

   * @buf: The output buffer to write to.
   *
   * This register holds the amount of system RAM to be tested during boot sequence.
   */

  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, "
  ");
  	
  	return out - buf;
  }
  
  /**

   * pdcs_osdep2_read - Stable Storage OS-Dependent data area 2 output.

   * @buf: The output buffer to write to.
   *
   * This can hold pdcs_size - 224 bytes of OS-Dependent data, when available.
   */

  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
  ", result);
  	}
  
  	return out - buf;
  }
  
  /**

   * pdcs_auto_write - This function handles autoboot/search flag modifying.

   * @buf: The input buffer to read from.
   * @count: The number of bytes to be read.

   * @knob: The PF_AUTOBOOT or PF_AUTOSEARCH flag

   * 

   * We will call this function to change the current autoboot flag.

   * We expect a precise syntax:

   *	\"n\" (n == 0 or 1) to toggle AutoBoot Off or On

   */

  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[8], *temp;

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

  	if (!buf || !count)

  		return -EINVAL;
  
  	/* We'll use a local copy of buf */

  	count = min_t(size_t, count, sizeof(in)-1);

  	strncpy(in, buf, count);

  	in[count] = '\0';

  
  	/* 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
  ", __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
  ", __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\"
  ",
  		(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)
  ", __func__);

  	return -EINVAL;
  }

  /**
   * pdcs_autoboot_write - This function handles autoboot flag modifying.

   * @buf: The input buffer to read from.
   * @count: The number of bytes to be read.
   *
   * We will call this function to change the current boot flags.
   * We expect a precise syntax:
   *	\"n\" (n == 0 or 1) to toggle AutoSearch Off or On
   */

  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);

  }
  
  /**
   * pdcs_autosearch_write - This function handles autosearch flag modifying.

   * @buf: The input buffer to read from.
   * @count: The number of bytes to be read.
   *
   * We will call this function to change the current boot flags.
   * We expect a precise syntax:
   *	\"n\" (n == 0 or 1) to toggle AutoSearch Off or On
   */

  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);

  }

  /**
   * pdcs_osdep1_write - Stable Storage OS-Dependent data area 1 input.

   * @buf: The input buffer to read from.
   * @count: The number of bytes to be read.
   *
   * This can store 16 bytes of OS-Dependent data. We use a byte-by-byte
   * write approach. It's up to userspace to deal with it when constructing
   * its input buffer.
   */

  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;
  }
  
  /**
   * pdcs_osdep2_write - Stable Storage OS-Dependent data area 2 input.

   * @buf: The input buffer to read from.
   * @count: The number of bytes to be read.
   *
   * This can store pdcs_size - 224 bytes of OS-Dependent data. We use a
   * byte-by-byte write approach. It's up to userspace to deal with it when
   * constructing its input buffer.
   */

  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 const struct attribute_group pdcs_attr_group = {

  	.attrs = pdcs_subsys_attrs,
  };

  static struct kobject *stable_kobj;

  static struct kset *paths_kset;

  
  /**
   * pdcs_register_pathentries - Prepares path entries kobjects for sysfs usage.
   * 
   * It creates kobjects corresponding to each path entry with nice sysfs
   * links to the real device. This is where the magic takes place: when
   * registering the subsystem attributes during module init, each kobject hereby
   * created will show in the sysfs tree as a folder containing files as defined
   * by path_subsys_attr[].
   */
  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;

  		write_unlock(&entry->rw_lock);

  		/* Add a nice symlink to the real device */

  		if (entry->dev) {
  			err = sysfs_create_link(&entry->kobj, &entry->dev->kobj, "device");
  			WARN_ON(err);
  		}

  		kobject_uevent(&entry->kobj, KOBJ_ADD);

  	}
  	
  	return 0;
  }
  
  /**
   * pdcs_unregister_pathentries - Routine called when unregistering the module.
   */

  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
  ", 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
  ");

  	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);