linux/drivers/w1/slaves/w1_ds2780.c
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

190 lines
4.1 KiB
C

/*
* 1-Wire implementation for the ds2780 chip
*
* Copyright (C) 2010 Indesign, LLC
*
* Author: Clifton Barnes <cabarnes@indesign-llc.com>
*
* Based on w1-ds2760 driver
*
* 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.
*
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/types.h>
#include <linux/platform_device.h>
#include <linux/mutex.h>
#include <linux/idr.h>
#include "../w1.h"
#include "../w1_int.h"
#include "../w1_family.h"
#include "w1_ds2780.h"
static int w1_ds2780_do_io(struct device *dev, char *buf, int addr,
size_t count, int io)
{
struct w1_slave *sl = container_of(dev, struct w1_slave, dev);
if (addr > DS2780_DATA_SIZE || addr < 0)
return 0;
count = min_t(int, count, DS2780_DATA_SIZE - addr);
if (w1_reset_select_slave(sl) == 0) {
if (io) {
w1_write_8(sl->master, W1_DS2780_WRITE_DATA);
w1_write_8(sl->master, addr);
w1_write_block(sl->master, buf, count);
} else {
w1_write_8(sl->master, W1_DS2780_READ_DATA);
w1_write_8(sl->master, addr);
count = w1_read_block(sl->master, buf, count);
}
}
return count;
}
int w1_ds2780_io(struct device *dev, char *buf, int addr, size_t count,
int io)
{
struct w1_slave *sl = container_of(dev, struct w1_slave, dev);
int ret;
if (!dev)
return -ENODEV;
mutex_lock(&sl->master->bus_mutex);
ret = w1_ds2780_do_io(dev, buf, addr, count, io);
mutex_unlock(&sl->master->bus_mutex);
return ret;
}
EXPORT_SYMBOL(w1_ds2780_io);
int w1_ds2780_eeprom_cmd(struct device *dev, int addr, int cmd)
{
struct w1_slave *sl = container_of(dev, struct w1_slave, dev);
if (!dev)
return -EINVAL;
mutex_lock(&sl->master->bus_mutex);
if (w1_reset_select_slave(sl) == 0) {
w1_write_8(sl->master, cmd);
w1_write_8(sl->master, addr);
}
mutex_unlock(&sl->master->bus_mutex);
return 0;
}
EXPORT_SYMBOL(w1_ds2780_eeprom_cmd);
static ssize_t w1_ds2780_read_bin(struct file *filp,
struct kobject *kobj,
struct bin_attribute *bin_attr,
char *buf, loff_t off, size_t count)
{
struct device *dev = container_of(kobj, struct device, kobj);
return w1_ds2780_io(dev, buf, off, count, 0);
}
static struct bin_attribute w1_ds2780_bin_attr = {
.attr = {
.name = "w1_slave",
.mode = S_IRUGO,
},
.size = DS2780_DATA_SIZE,
.read = w1_ds2780_read_bin,
};
static DEFINE_IDA(bat_ida);
static int w1_ds2780_add_slave(struct w1_slave *sl)
{
int ret;
int id;
struct platform_device *pdev;
id = ida_simple_get(&bat_ida, 0, 0, GFP_KERNEL);
if (id < 0) {
ret = id;
goto noid;
}
pdev = platform_device_alloc("ds2780-battery", id);
if (!pdev) {
ret = -ENOMEM;
goto pdev_alloc_failed;
}
pdev->dev.parent = &sl->dev;
ret = platform_device_add(pdev);
if (ret)
goto pdev_add_failed;
ret = sysfs_create_bin_file(&sl->dev.kobj, &w1_ds2780_bin_attr);
if (ret)
goto bin_attr_failed;
dev_set_drvdata(&sl->dev, pdev);
return 0;
bin_attr_failed:
pdev_add_failed:
platform_device_unregister(pdev);
pdev_alloc_failed:
ida_simple_remove(&bat_ida, id);
noid:
return ret;
}
static void w1_ds2780_remove_slave(struct w1_slave *sl)
{
struct platform_device *pdev = dev_get_drvdata(&sl->dev);
int id = pdev->id;
platform_device_unregister(pdev);
ida_simple_remove(&bat_ida, id);
sysfs_remove_bin_file(&sl->dev.kobj, &w1_ds2780_bin_attr);
}
static struct w1_family_ops w1_ds2780_fops = {
.add_slave = w1_ds2780_add_slave,
.remove_slave = w1_ds2780_remove_slave,
};
static struct w1_family w1_ds2780_family = {
.fid = W1_FAMILY_DS2780,
.fops = &w1_ds2780_fops,
};
static int __init w1_ds2780_init(void)
{
ida_init(&bat_ida);
return w1_register_family(&w1_ds2780_family);
}
static void __exit w1_ds2780_exit(void)
{
w1_unregister_family(&w1_ds2780_family);
ida_destroy(&bat_ida);
}
module_init(w1_ds2780_init);
module_exit(w1_ds2780_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Clifton Barnes <cabarnes@indesign-llc.com>");
MODULE_DESCRIPTION("1-wire Driver for Maxim/Dallas DS2780 Stand-Alone Fuel Gauge IC");