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linux/drivers/w1/w1.h
NeilBrown b02f8bede2 W1: split master mutex to avoid deadlocks. 
The 'mutex' in struct w1_master is use for two very different
purposes.

Firstly it protects various data structures such as the list of all
slaves.

Secondly it protects the w1 buss against concurrent accesses.

This can lead to deadlocks when the ->probe code called while adding a
slave needs to talk on the bus, as is the case for power_supply
devices.
ds2780 and ds2781 drivers contain a work around to track which
process hold the lock simply to avoid this deadlock.  bq27000 doesn't
have that work around and so deadlocks.

There are other possible deadlocks involving sysfs.
When removing a device the sysfs s_active lock is held, so the lock
that protects the slave list must take precedence over s_active.
However when access power_supply attributes via sysfs, the s_active
lock must take precedence over the lock that protects accesses to
the bus.

So to avoid deadlocks between w1 slaves and sysfs, these must be
two separate locks.  Making them separate means that the work around
in ds2780 and ds2781 can be removed.

So this patch:
 - adds a new mutex: "bus_mutex" which serialises access to the bus.
 - takes in mutex in w1_search and ds1wm_search while they access
   the bus for searching.  The mutex is dropped before calling the
   callback which adds the slave.
 - changes all slaves to use bus_mutex instead of mutex to
   protect access to the bus
 - removes w1_ds2790_io_nolock and w1_ds2781_io_nolock, and the
   related code from drivers/power/ds278[01]_battery.c which
   calls them.

Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-06-13 16:38:40 -07:00

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/*
* w1.h
*
* Copyright (c) 2004 Evgeniy Polyakov <zbr@ioremap.net>
*
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* 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
*/
#ifndef __W1_H
#define __W1_H
struct w1_reg_num
{
#if defined(__LITTLE_ENDIAN_BITFIELD)
__u64 family:8,
id:48,
crc:8;
#elif defined(__BIG_ENDIAN_BITFIELD)
__u64 crc:8,
id:48,
family:8;
#else
#error "Please fix <asm/byteorder.h>"
#endif
};
#ifdef __KERNEL__
#include <linux/completion.h>
#include <linux/device.h>
#include <linux/mutex.h>
#include "w1_family.h"
#define W1_MAXNAMELEN 32
#define W1_SEARCH 0xF0
#define W1_ALARM_SEARCH 0xEC
#define W1_CONVERT_TEMP 0x44
#define W1_SKIP_ROM 0xCC
#define W1_READ_SCRATCHPAD 0xBE
#define W1_READ_ROM 0x33
#define W1_READ_PSUPPLY 0xB4
#define W1_MATCH_ROM 0x55
#define W1_RESUME_CMD 0xA5
#define W1_SLAVE_ACTIVE 0
struct w1_slave
{
struct module *owner;
unsigned char name[W1_MAXNAMELEN];
struct list_head w1_slave_entry;
struct w1_reg_num reg_num;
atomic_t refcnt;
u8 rom[9];
u32 flags;
int ttl;
struct w1_master *master;
struct w1_family *family;
void *family_data;
struct device dev;
struct completion released;
};
typedef void (*w1_slave_found_callback)(struct w1_master *, u64);
/**
* Note: read_bit and write_bit are very low level functions and should only
* be used with hardware that doesn't really support 1-wire operations,
* like a parallel/serial port.
* Either define read_bit and write_bit OR define, at minimum, touch_bit and
* reset_bus.
*/
struct w1_bus_master
{
/** the first parameter in all the functions below */
void *data;
/**
* Sample the line level
* @return the level read (0 or 1)
*/
u8 (*read_bit)(void *);
/** Sets the line level */
void (*write_bit)(void *, u8);
/**
* touch_bit is the lowest-level function for devices that really
* support the 1-wire protocol.
* touch_bit(0) = write-0 cycle
* touch_bit(1) = write-1 / read cycle
* @return the bit read (0 or 1)
*/
u8 (*touch_bit)(void *, u8);
/**
* Reads a bytes. Same as 8 touch_bit(1) calls.
* @return the byte read
*/
u8 (*read_byte)(void *);
/**
* Writes a byte. Same as 8 touch_bit(x) calls.
*/
void (*write_byte)(void *, u8);
/**
* Same as a series of read_byte() calls
* @return the number of bytes read
*/
u8 (*read_block)(void *, u8 *, int);
/** Same as a series of write_byte() calls */
void (*write_block)(void *, const u8 *, int);
/**
* Combines two reads and a smart write for ROM searches
* @return bit0=Id bit1=comp_id bit2=dir_taken
*/
u8 (*triplet)(void *, u8);
/**
* long write-0 with a read for the presence pulse detection
* @return -1=Error, 0=Device present, 1=No device present
*/
u8 (*reset_bus)(void *);
/**
* Put out a strong pull-up pulse of the specified duration.
* @return -1=Error, 0=completed
*/
u8 (*set_pullup)(void *, int);
/** Really nice hardware can handles the different types of ROM search
* w1_master* is passed to the slave found callback.
*/
void (*search)(void *, struct w1_master *,
u8, w1_slave_found_callback);
};
struct w1_master
{
struct list_head w1_master_entry;
struct module *owner;
unsigned char name[W1_MAXNAMELEN];
struct list_head slist;
int max_slave_count, slave_count;
unsigned long attempts;
int slave_ttl;
int initialized;
u32 id;
int search_count;
atomic_t refcnt;
void *priv;
int priv_size;
/** 5V strong pullup enabled flag, 1 enabled, zero disabled. */
int enable_pullup;
/** 5V strong pullup duration in milliseconds, zero disabled. */
int pullup_duration;
struct task_struct *thread;
struct mutex mutex;
struct mutex bus_mutex;
struct device_driver *driver;
struct device dev;
struct w1_bus_master *bus_master;
u32 seq;
};
int w1_create_master_attributes(struct w1_master *);
void w1_destroy_master_attributes(struct w1_master *master);
void w1_search(struct w1_master *dev, u8 search_type, w1_slave_found_callback cb);
void w1_search_devices(struct w1_master *dev, u8 search_type, w1_slave_found_callback cb);
struct w1_slave *w1_search_slave(struct w1_reg_num *id);
void w1_slave_found(struct w1_master *dev, u64 rn);
void w1_search_process_cb(struct w1_master *dev, u8 search_type,
w1_slave_found_callback cb);
struct w1_master *w1_search_master_id(u32 id);
/* Disconnect and reconnect devices in the given family. Used for finding
* unclaimed devices after a family has been registered or releasing devices
* after a family has been unregistered. Set attach to 1 when a new family
* has just been registered, to 0 when it has been unregistered.
*/
void w1_reconnect_slaves(struct w1_family *f, int attach);
void w1_slave_detach(struct w1_slave *sl);
u8 w1_triplet(struct w1_master *dev, int bdir);
void w1_write_8(struct w1_master *, u8);
u8 w1_read_8(struct w1_master *);
int w1_reset_bus(struct w1_master *);
u8 w1_calc_crc8(u8 *, int);
void w1_write_block(struct w1_master *, const u8 *, int);
void w1_touch_block(struct w1_master *, u8 *, int);
u8 w1_read_block(struct w1_master *, u8 *, int);
int w1_reset_select_slave(struct w1_slave *sl);
int w1_reset_resume_command(struct w1_master *);
void w1_next_pullup(struct w1_master *, int);
static inline struct w1_slave* dev_to_w1_slave(struct device *dev)
{
return container_of(dev, struct w1_slave, dev);
}
static inline struct w1_slave* kobj_to_w1_slave(struct kobject *kobj)
{
return dev_to_w1_slave(container_of(kobj, struct device, kobj));
}
static inline struct w1_master* dev_to_w1_master(struct device *dev)
{
return container_of(dev, struct w1_master, dev);
}
extern struct device_driver w1_master_driver;
extern struct device w1_master_device;
extern int w1_max_slave_count;
extern int w1_max_slave_ttl;
extern struct list_head w1_masters;
extern struct mutex w1_mlock;
extern int w1_process(void *);
#endif /* __KERNEL__ */
#endif /* __W1_H */
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