linux/drivers/w1/slaves/w1_ds2423.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

166 lines
4.3 KiB
C

/*
* w1_ds2423.c
*
* Copyright (c) 2010 Mika Laitio <lamikr@pilppa.org>
*
* This driver will read and write the value of 4 counters to w1_slave file in
* sys filesystem.
* Inspired by the w1_therm and w1_ds2431 drivers.
*
* This program is free software; you can redistribute it and/or modify
* it under the therms 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
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/device.h>
#include <linux/types.h>
#include <linux/delay.h>
#include <linux/crc16.h>
#include "../w1.h"
#include "../w1_int.h"
#include "../w1_family.h"
#define CRC16_VALID 0xb001
#define CRC16_INIT 0
#define COUNTER_COUNT 4
#define READ_BYTE_COUNT 42
static ssize_t w1_counter_read(struct device *device,
struct device_attribute *attr, char *buf);
static struct device_attribute w1_counter_attr =
__ATTR(w1_slave, S_IRUGO, w1_counter_read, NULL);
static ssize_t w1_counter_read(struct device *device,
struct device_attribute *attr, char *out_buf)
{
struct w1_slave *sl = dev_to_w1_slave(device);
struct w1_master *dev = sl->master;
u8 rbuf[COUNTER_COUNT * READ_BYTE_COUNT];
u8 wrbuf[3];
int rom_addr;
int read_byte_count;
int result;
ssize_t c;
int ii;
int p;
int crc;
c = PAGE_SIZE;
rom_addr = (12 << 5) + 31;
wrbuf[0] = 0xA5;
wrbuf[1] = rom_addr & 0xFF;
wrbuf[2] = rom_addr >> 8;
mutex_lock(&dev->bus_mutex);
if (!w1_reset_select_slave(sl)) {
w1_write_block(dev, wrbuf, 3);
read_byte_count = 0;
for (p = 0; p < 4; p++) {
/*
* 1 byte for first bytes in ram page read
* 4 bytes for counter
* 4 bytes for zero bits
* 2 bytes for crc
* 31 remaining bytes from the ram page
*/
read_byte_count += w1_read_block(dev,
rbuf + (p * READ_BYTE_COUNT), READ_BYTE_COUNT);
for (ii = 0; ii < READ_BYTE_COUNT; ++ii)
c -= snprintf(out_buf + PAGE_SIZE - c,
c, "%02x ",
rbuf[(p * READ_BYTE_COUNT) + ii]);
if (read_byte_count != (p + 1) * READ_BYTE_COUNT) {
dev_warn(device,
"w1_counter_read() returned %u bytes "
"instead of %d bytes wanted.\n",
read_byte_count,
READ_BYTE_COUNT);
c -= snprintf(out_buf + PAGE_SIZE - c,
c, "crc=NO\n");
} else {
if (p == 0) {
crc = crc16(CRC16_INIT, wrbuf, 3);
crc = crc16(crc, rbuf, 11);
} else {
/*
* DS2423 calculates crc from all bytes
* read after the previous crc bytes.
*/
crc = crc16(CRC16_INIT,
(rbuf + 11) +
((p - 1) * READ_BYTE_COUNT),
READ_BYTE_COUNT);
}
if (crc == CRC16_VALID) {
result = 0;
for (ii = 4; ii > 0; ii--) {
result <<= 8;
result |= rbuf[(p *
READ_BYTE_COUNT) + ii];
}
c -= snprintf(out_buf + PAGE_SIZE - c,
c, "crc=YES c=%d\n", result);
} else {
c -= snprintf(out_buf + PAGE_SIZE - c,
c, "crc=NO\n");
}
}
}
} else {
c -= snprintf(out_buf + PAGE_SIZE - c, c, "Connection error");
}
mutex_unlock(&dev->bus_mutex);
return PAGE_SIZE - c;
}
static int w1_f1d_add_slave(struct w1_slave *sl)
{
return device_create_file(&sl->dev, &w1_counter_attr);
}
static void w1_f1d_remove_slave(struct w1_slave *sl)
{
device_remove_file(&sl->dev, &w1_counter_attr);
}
static struct w1_family_ops w1_f1d_fops = {
.add_slave = w1_f1d_add_slave,
.remove_slave = w1_f1d_remove_slave,
};
static struct w1_family w1_family_1d = {
.fid = W1_COUNTER_DS2423,
.fops = &w1_f1d_fops,
};
static int __init w1_f1d_init(void)
{
return w1_register_family(&w1_family_1d);
}
static void __exit w1_f1d_exit(void)
{
w1_unregister_family(&w1_family_1d);
}
module_init(w1_f1d_init);
module_exit(w1_f1d_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Mika Laitio <lamikr@pilppa.org>");
MODULE_DESCRIPTION("w1 family 1d driver for DS2423, 4 counters and 4kb ram");