1/*
2 *	w1_ds2423.c
3 *
4 * Copyright (c) 2010 Mika Laitio <lamikr@pilppa.org>
5 *
6 * This driver will read and write the value of 4 counters to w1_slave file in
7 * sys filesystem.
8 * Inspired by the w1_therm and w1_ds2431 drivers.
9 *
10 * This program is free software; you can redistribute it and/or modify
11 * it under the therms of the GNU General Public License as published by
12 * the Free Software Foundation; either version 2 of the License, or
13 * (at your option) any later version.
14 *
15 * This program is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
18 * GNU General Public License for more details.
19 *
20 * You should have received a copy of the GNU General Public License
21 * along with this program; if not, write to the Free Software
22 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
23 */
24
25#include <linux/kernel.h>
26#include <linux/module.h>
27#include <linux/moduleparam.h>
28#include <linux/device.h>
29#include <linux/types.h>
30#include <linux/delay.h>
31#include <linux/crc16.h>
32
33#include "../w1.h"
34#include "../w1_int.h"
35#include "../w1_family.h"
36
37#define CRC16_VALID	0xb001
38#define CRC16_INIT	0
39
40#define COUNTER_COUNT 4
41#define READ_BYTE_COUNT 42
42
43static ssize_t w1_slave_show(struct device *device,
44			     struct device_attribute *attr, char *out_buf)
45{
46	struct w1_slave *sl = dev_to_w1_slave(device);
47	struct w1_master *dev = sl->master;
48	u8 rbuf[COUNTER_COUNT * READ_BYTE_COUNT];
49	u8 wrbuf[3];
50	int rom_addr;
51	int read_byte_count;
52	int result;
53	ssize_t c;
54	int ii;
55	int p;
56	int crc;
57
58	c		= PAGE_SIZE;
59	rom_addr	= (12 << 5) + 31;
60	wrbuf[0]	= 0xA5;
61	wrbuf[1]	= rom_addr & 0xFF;
62	wrbuf[2]	= rom_addr >> 8;
63	mutex_lock(&dev->bus_mutex);
64	if (!w1_reset_select_slave(sl)) {
65		w1_write_block(dev, wrbuf, 3);
66		read_byte_count = 0;
67		for (p = 0; p < 4; p++) {
68			/*
69			 * 1 byte for first bytes in ram page read
70			 * 4 bytes for counter
71			 * 4 bytes for zero bits
72			 * 2 bytes for crc
73			 * 31 remaining bytes from the ram page
74			 */
75			read_byte_count += w1_read_block(dev,
76				rbuf + (p * READ_BYTE_COUNT), READ_BYTE_COUNT);
77			for (ii = 0; ii < READ_BYTE_COUNT; ++ii)
78				c -= snprintf(out_buf + PAGE_SIZE - c,
79					c, "%02x ",
80					rbuf[(p * READ_BYTE_COUNT) + ii]);
81			if (read_byte_count != (p + 1) * READ_BYTE_COUNT) {
82				dev_warn(device,
83					"w1_counter_read() returned %u bytes "
84					"instead of %d bytes wanted.\n",
85					read_byte_count,
86					READ_BYTE_COUNT);
87				c -= snprintf(out_buf + PAGE_SIZE - c,
88					c, "crc=NO\n");
89			} else {
90				if (p == 0) {
91					crc = crc16(CRC16_INIT, wrbuf, 3);
92					crc = crc16(crc, rbuf, 11);
93				} else {
94					/*
95					 * DS2423 calculates crc from all bytes
96					 * read after the previous crc bytes.
97					 */
98					crc = crc16(CRC16_INIT,
99						(rbuf + 11) +
100						((p - 1) * READ_BYTE_COUNT),
101						READ_BYTE_COUNT);
102				}
103				if (crc == CRC16_VALID) {
104					result = 0;
105					for (ii = 4; ii > 0; ii--) {
106						result <<= 8;
107						result |= rbuf[(p *
108							READ_BYTE_COUNT) + ii];
109					}
110					c -= snprintf(out_buf + PAGE_SIZE - c,
111						c, "crc=YES c=%d\n", result);
112				} else {
113					c -= snprintf(out_buf + PAGE_SIZE - c,
114						c, "crc=NO\n");
115				}
116			}
117		}
118	} else {
119		c -= snprintf(out_buf + PAGE_SIZE - c, c, "Connection error");
120	}
121	mutex_unlock(&dev->bus_mutex);
122	return PAGE_SIZE - c;
123}
124
125static DEVICE_ATTR_RO(w1_slave);
126
127static struct attribute *w1_f1d_attrs[] = {
128	&dev_attr_w1_slave.attr,
129	NULL,
130};
131ATTRIBUTE_GROUPS(w1_f1d);
132
133static struct w1_family_ops w1_f1d_fops = {
134	.groups		= w1_f1d_groups,
135};
136
137static struct w1_family w1_family_1d = {
138	.fid = W1_COUNTER_DS2423,
139	.fops = &w1_f1d_fops,
140};
141
142static int __init w1_f1d_init(void)
143{
144	return w1_register_family(&w1_family_1d);
145}
146
147static void __exit w1_f1d_exit(void)
148{
149	w1_unregister_family(&w1_family_1d);
150}
151
152module_init(w1_f1d_init);
153module_exit(w1_f1d_exit);
154
155MODULE_LICENSE("GPL");
156MODULE_AUTHOR("Mika Laitio <lamikr@pilppa.org>");
157MODULE_DESCRIPTION("w1 family 1d driver for DS2423, 4 counters and 4kb ram");
158MODULE_ALIAS("w1-family-" __stringify(W1_COUNTER_DS2423));
159