ads7828.c revision 145980a0b07520f0f82cc40999acc92b349ea40c 
1/*
2	ads7828.c - lm_sensors driver for ads7828 12-bit 8-channel ADC
3	(C) 2007 EADS Astrium
4
5	This driver is based on the lm75 and other lm_sensors/hwmon drivers
6
7	Written by Steve Hardy <steve@linuxrealtime.co.uk>
8
9	Datasheet available at: http://focus.ti.com/lit/ds/symlink/ads7828.pdf
10
11	This program is free software; you can redistribute it and/or modify
12	it under the terms of the GNU General Public License as published by
13	the Free Software Foundation; either version 2 of the License, or
14	(at your option) any later version.
15
16	This program is distributed in the hope that it will be useful,
17	but WITHOUT ANY WARRANTY; without even the implied warranty of
18	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	See the
19	GNU General Public License for more details.
20
21	You should have received a copy of the GNU General Public License
22	along with this program; if not, write to the Free Software
23	Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24*/
25
26#include <linux/module.h>
27#include <linux/init.h>
28#include <linux/slab.h>
29#include <linux/jiffies.h>
30#include <linux/i2c.h>
31#include <linux/hwmon.h>
32#include <linux/hwmon-sysfs.h>
33#include <linux/err.h>
34#include <linux/mutex.h>
35
36/* The ADS7828 registers */
37#define ADS7828_NCH 8 /* 8 channels of 12-bit A-D supported */
38#define ADS7828_CMD_SD_SE 0x80 /* Single ended inputs */
39#define ADS7828_CMD_SD_DIFF 0x00 /* Differential inputs */
40#define ADS7828_CMD_PD0 0x0 /* Power Down between A-D conversions */
41#define ADS7828_CMD_PD1 0x04 /* Internal ref OFF && A-D ON */
42#define ADS7828_CMD_PD2 0x08 /* Internal ref ON && A-D OFF */
43#define ADS7828_CMD_PD3 0x0C /* Internal ref ON && A-D ON */
44#define ADS7828_INT_VREF_MV 2500 /* Internal vref is 2.5V, 2500mV */
45
46/* Addresses to scan */
47static const unsigned short normal_i2c[] = { 0x48, 0x49, 0x4a, 0x4b,
48	I2C_CLIENT_END };
49
50/* Insmod parameters */
51I2C_CLIENT_INSMOD_1(ads7828);
52
53/* Other module parameters */
54static int se_input = 1; /* Default is SE, 0 == diff */
55static int int_vref = 1; /* Default is internal ref ON */
56static int vref_mv = ADS7828_INT_VREF_MV; /* set if vref != 2.5V */
57module_param(se_input, bool, S_IRUGO);
58module_param(int_vref, bool, S_IRUGO);
59module_param(vref_mv, int, S_IRUGO);
60
61/* Global Variables */
62static u8 ads7828_cmd_byte; /* cmd byte without channel bits */
63static unsigned int ads7828_lsb_resol; /* resolution of the ADC sample lsb */
64
65/* Each client has this additional data */
66struct ads7828_data {
67	struct i2c_client client;
68	struct device *hwmon_dev;
69	struct mutex update_lock; /* mutex protect updates */
70	char valid; /* !=0 if following fields are valid */
71	unsigned long last_updated; /* In jiffies */
72	u16 adc_input[ADS7828_NCH]; /* ADS7828_NCH 12-bit samples */
73};
74
75/* Function declaration - necessary due to function dependencies */
76static int ads7828_detect(struct i2c_adapter *adapter, int address, int kind);
77
78/* The ADS7828 returns the 12-bit sample in two bytes,
79	these are read as a word then byte-swapped */
80static u16 ads7828_read_value(struct i2c_client *client, u8 reg)
81{
82	return swab16(i2c_smbus_read_word_data(client, reg));
83}
84
85static inline u8 channel_cmd_byte(int ch)
86{
87	/* cmd byte C2,C1,C0 - see datasheet */
88	u8 cmd = (((ch>>1) | (ch&0x01)<<2)<<4);
89	cmd |= ads7828_cmd_byte;
90	return cmd;
91}
92
93/* Update data for the device (all 8 channels) */
94static struct ads7828_data *ads7828_update_device(struct device *dev)
95{
96	struct i2c_client *client = to_i2c_client(dev);
97	struct ads7828_data *data = i2c_get_clientdata(client);
98
99	mutex_lock(&data->update_lock);
100
101	if (time_after(jiffies, data->last_updated + HZ + HZ / 2)
102			|| !data->valid) {
103		unsigned int ch;
104		dev_dbg(&client->dev, "Starting ads7828 update\n");
105
106		for (ch = 0; ch < ADS7828_NCH; ch++) {
107			u8 cmd = channel_cmd_byte(ch);
108			data->adc_input[ch] = ads7828_read_value(client, cmd);
109		}
110		data->last_updated = jiffies;
111		data->valid = 1;
112	}
113
114	mutex_unlock(&data->update_lock);
115
116	return data;
117}
118
119/* sysfs callback function */
120static ssize_t show_in(struct device *dev, struct device_attribute *da,
121	char *buf)
122{
123	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
124	struct ads7828_data *data = ads7828_update_device(dev);
125	/* Print value (in mV as specified in sysfs-interface documentation) */
126	return sprintf(buf, "%d\n", (data->adc_input[attr->index] *
127		ads7828_lsb_resol)/1000);
128}
129
130#define in_reg(offset)\
131static SENSOR_DEVICE_ATTR(in##offset##_input, S_IRUGO, show_in,\
132	NULL, offset)
133
134in_reg(0);
135in_reg(1);
136in_reg(2);
137in_reg(3);
138in_reg(4);
139in_reg(5);
140in_reg(6);
141in_reg(7);
142
143static struct attribute *ads7828_attributes[] = {
144	&sensor_dev_attr_in0_input.dev_attr.attr,
145	&sensor_dev_attr_in1_input.dev_attr.attr,
146	&sensor_dev_attr_in2_input.dev_attr.attr,
147	&sensor_dev_attr_in3_input.dev_attr.attr,
148	&sensor_dev_attr_in4_input.dev_attr.attr,
149	&sensor_dev_attr_in5_input.dev_attr.attr,
150	&sensor_dev_attr_in6_input.dev_attr.attr,
151	&sensor_dev_attr_in7_input.dev_attr.attr,
152	NULL
153};
154
155static const struct attribute_group ads7828_group = {
156	.attrs = ads7828_attributes,
157};
158
159static int ads7828_attach_adapter(struct i2c_adapter *adapter)
160{
161	if (!(adapter->class & I2C_CLASS_HWMON))
162		return 0;
163	return i2c_probe(adapter, &addr_data, ads7828_detect);
164}
165
166static int ads7828_detach_client(struct i2c_client *client)
167{
168	struct ads7828_data *data = i2c_get_clientdata(client);
169	hwmon_device_unregister(data->hwmon_dev);
170	sysfs_remove_group(&client->dev.kobj, &ads7828_group);
171	i2c_detach_client(client);
172	kfree(i2c_get_clientdata(client));
173	return 0;
174}
175
176/* This is the driver that will be inserted */
177static struct i2c_driver ads7828_driver = {
178	.driver = {
179		.name = "ads7828",
180	},
181	.attach_adapter = ads7828_attach_adapter,
182	.detach_client = ads7828_detach_client,
183};
184
185/* This function is called by i2c_probe */
186static int ads7828_detect(struct i2c_adapter *adapter, int address, int kind)
187{
188	struct i2c_client *client;
189	struct ads7828_data *data;
190	int err = 0;
191	const char *name = "";
192
193	/* Check we have a valid client */
194	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_WORD_DATA))
195		goto exit;
196
197	/* OK. For now, we presume we have a valid client. We now create the
198	client structure, even though we cannot fill it completely yet.
199	But it allows us to access ads7828_read_value. */
200	data = kzalloc(sizeof(struct ads7828_data), GFP_KERNEL);
201	if (!data) {
202		err = -ENOMEM;
203		goto exit;
204	}
205
206	client = &data->client;
207	i2c_set_clientdata(client, data);
208	client->addr = address;
209	client->adapter = adapter;
210	client->driver = &ads7828_driver;
211
212	/* Now, we do the remaining detection. There is no identification
213	dedicated register so attempt to sanity check using knowledge of
214	the chip
215	- Read from the 8 channel addresses
216	- Check the top 4 bits of each result are not set (12 data bits)
217	*/
218	if (kind < 0) {
219		int ch;
220		for (ch = 0; ch < ADS7828_NCH; ch++) {
221			u16 in_data;
222			u8 cmd = channel_cmd_byte(ch);
223			in_data = ads7828_read_value(client, cmd);
224			if (in_data & 0xF000) {
225				printk(KERN_DEBUG
226				"%s : Doesn't look like an ads7828 device\n",
227				__func__);
228				goto exit_free;
229			}
230		}
231	}
232
233	/* Determine the chip type - only one kind supported! */
234	if (kind <= 0)
235		kind = ads7828;
236
237	if (kind == ads7828)
238		name = "ads7828";
239
240	/* Fill in the remaining client fields, put it into the global list */
241	strlcpy(client->name, name, I2C_NAME_SIZE);
242
243	mutex_init(&data->update_lock);
244
245	/* Tell the I2C layer a new client has arrived */
246	err = i2c_attach_client(client);
247	if (err)
248		goto exit_free;
249
250	/* Register sysfs hooks */
251	err = sysfs_create_group(&client->dev.kobj, &ads7828_group);
252	if (err)
253		goto exit_detach;
254
255	data->hwmon_dev = hwmon_device_register(&client->dev);
256	if (IS_ERR(data->hwmon_dev)) {
257		err = PTR_ERR(data->hwmon_dev);
258		goto exit_remove;
259	}
260
261	return 0;
262
263exit_remove:
264	sysfs_remove_group(&client->dev.kobj, &ads7828_group);
265exit_detach:
266	i2c_detach_client(client);
267exit_free:
268	kfree(data);
269exit:
270	return err;
271}
272
273static int __init sensors_ads7828_init(void)
274{
275	/* Initialize the command byte according to module parameters */
276	ads7828_cmd_byte = se_input ?
277		ADS7828_CMD_SD_SE : ADS7828_CMD_SD_DIFF;
278	ads7828_cmd_byte |= int_vref ?
279		ADS7828_CMD_PD3 : ADS7828_CMD_PD1;
280
281	/* Calculate the LSB resolution */
282	ads7828_lsb_resol = (vref_mv*1000)/4096;
283
284	return i2c_add_driver(&ads7828_driver);
285}
286
287static void __exit sensors_ads7828_exit(void)
288{
289	i2c_del_driver(&ads7828_driver);
290}
291
292MODULE_AUTHOR("Steve Hardy <steve@linuxrealtime.co.uk>");
293MODULE_DESCRIPTION("ADS7828 driver");
294MODULE_LICENSE("GPL");
295
296module_init(sensors_ads7828_init);
297module_exit(sensors_ads7828_exit);
298