Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1094 insertions, 0 deletions

diff --git a/drivers/parisc/pdc_stable.c b/drivers/parisc/pdc_stable.c
new file mode 100644
index 000000000..d6af5726d
--- /dev/null
+++ b/drivers/parisc/pdc_stable.c
@@ -0,0 +1,1094 @@
+// 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
+ *    pdc_module_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 pdc_module_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 pdc_module_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 pdc_module_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;
+}
+
+/**
+ * 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 pdc_module_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)
+		WARN(1, 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__);
+		
+	/* kobject is already registered */
+	entry->ready = 2;
+	
+	DPRINTK("%s: device: 0x%p\n", __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 pdc_module_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->path.bc[i] < 0)
+			continue;
+		out += sprintf(out, "%d/", devpath->path.bc[i]);
+	}
+	out += sprintf(out, "%u\n", (unsigned char)devpath->path.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\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.path.bc[i]);
+	}
+	
+	/* Store the final field */		
+	hwpath.bc[i] = simple_strtoul(in, NULL, 10);
+	DPRINTK("%s: bc[%d]: %d\n", __func__, i, hwpath.path.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");
+	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\"\n",
+		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 pdc_module_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;
+}
+
+/**
+ * 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\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;
+}
+
+/**
+ * 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,
+};
+ATTRIBUTE_GROUPS(paths_subsys);
+
+/* Specific kobject type for our PDC paths */
+static struct kobj_type ktype_pdcspath = {
+	.sysfs_ops = &pdcspath_attr_ops,
+	.default_groups = paths_subsys_groups,
+};
+
+/* 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\n", 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\n", (pathentry->devpath.path.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\n", (pathentry->devpath.path.flags & PF_TIMER) ?
+				(1 << (pathentry->devpath.path.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)\n",
+		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\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;
+}
+
+/**
+ * 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\n", (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, "\n");
+	
+	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\n", 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.path.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.path.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;
+}
+
+/**
+ * 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) {
+			kobject_put(&entry->kobj);
+			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\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);