pdc_stable.c

linux 内核源代码

/* 
 *    Interfaces to retrieve and set PDC Stable options (firmware)
 *
 *    Copyright (C) 2005-2006 Thibaut VARENE <[e-mail]>
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License, version 2, as
 *    published by the Free Software Foundation.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *
 *    DEV NOTE: the PDC Procedures reference states that:
 *    "A minimum of 96 bytes of Stable Storage is required. Providing more than
 *    96 bytes of Stable Storage is optional [...]. Failure to provide the
 *    optional locations from 96 to 192 results in the loss of certain
 *    functionality during boot."
 *
 *    Since locations between 96 and 192 are the various paths, most (if not
 *    all) PA-RISC machines should have them. Anyway, for safety reasons, the
 *    following code can deal with just 96 bytes of Stable Storage, and all
 *    sizes between 96 and 192 bytes (provided they are multiple of struct
 *    device_path size, eg: 128, 160 and 192) to provide full information.
 *    One last word: there's one path we can always count on: the primary path.
 *    Anything above 224 bytes is used for 'osdep2' OS-dependent storage area.
 *
 *    The first OS-dependent area should always be available. Obviously, this is
 *    not true for the other one. Also bear in mind that reading/writing from/to
 *    osdep2 is much more expensive than from/to osdep1.
 *    NOTE: We do not handle the 2 bytes OS-dep area at 0x5D, nor the first
 *    2 bytes of storage available right after OSID. That's a total of 4 bytes
 *    sacrificed: -ETOOLAZY :P
 *
 *    The current policy wrt file permissions is:
 *	- write: root only
 *	- read: (reading triggers PDC calls) ? root only : everyone
 *    The rationale is that PDC calls could hog (DoS) the machine.
 *
 *	TODO:
 *	- timer/fastsize write calls
 */

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

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

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

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

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

MODULE_AUTHOR("Thibaut VARENE <[e-mail]>");
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 subsys_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 facilites. 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) {
		printk(KERN_ERR "%s: an error occured when writing to PDC.\n"
				"It is likely that the Stable Storage data has been corrupted.\n"
				"Please check it carefully upon next reboot.\n", __func__);
		WARN_ON(1);
	}
		
	/* kobject is already registered */
	entry->ready = 2;
	
	DPRINTK("%s: device: 0x%p\n", __func__, entry->dev);
}

/**
 * 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[count+1], *temp;
	struct device *dev;
	int ret;

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

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

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

/**
 * 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 */