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 // 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\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;
 }
 
 /**
  * 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\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 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;
 }
 
 /**
  * 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.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");
     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 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;
 }
 
 /**
  * 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.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.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)\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.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;
 }
 
 /**
  * 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);

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