Loading...
1/*
2 * I2C multiplexer driver for PCA9541 bus master selector
3 *
4 * Copyright (c) 2010 Ericsson AB.
5 *
6 * Author: Guenter Roeck <linux@roeck-us.net>
7 *
8 * Derived from:
9 * pca954x.c
10 *
11 * Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
12 * Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
13 *
14 * This file is licensed under the terms of the GNU General Public
15 * License version 2. This program is licensed "as is" without any
16 * warranty of any kind, whether express or implied.
17 */
18
19#include <linux/bitops.h>
20#include <linux/delay.h>
21#include <linux/device.h>
22#include <linux/i2c.h>
23#include <linux/i2c-mux.h>
24#include <linux/jiffies.h>
25#include <linux/module.h>
26#include <linux/slab.h>
27
28/*
29 * The PCA9541 is a bus master selector. It supports two I2C masters connected
30 * to a single slave bus.
31 *
32 * Before each bus transaction, a master has to acquire bus ownership. After the
33 * transaction is complete, bus ownership has to be released. This fits well
34 * into the I2C multiplexer framework, which provides select and release
35 * functions for this purpose. For this reason, this driver is modeled as
36 * single-channel I2C bus multiplexer.
37 *
38 * This driver assumes that the two bus masters are controlled by two different
39 * hosts. If a single host controls both masters, platform code has to ensure
40 * that only one of the masters is instantiated at any given time.
41 */
42
43#define PCA9541_CONTROL 0x01
44#define PCA9541_ISTAT 0x02
45
46#define PCA9541_CTL_MYBUS BIT(0)
47#define PCA9541_CTL_NMYBUS BIT(1)
48#define PCA9541_CTL_BUSON BIT(2)
49#define PCA9541_CTL_NBUSON BIT(3)
50#define PCA9541_CTL_BUSINIT BIT(4)
51#define PCA9541_CTL_TESTON BIT(6)
52#define PCA9541_CTL_NTESTON BIT(7)
53
54#define PCA9541_ISTAT_INTIN BIT(0)
55#define PCA9541_ISTAT_BUSINIT BIT(1)
56#define PCA9541_ISTAT_BUSOK BIT(2)
57#define PCA9541_ISTAT_BUSLOST BIT(3)
58#define PCA9541_ISTAT_MYTEST BIT(6)
59#define PCA9541_ISTAT_NMYTEST BIT(7)
60
61#define BUSON (PCA9541_CTL_BUSON | PCA9541_CTL_NBUSON)
62#define MYBUS (PCA9541_CTL_MYBUS | PCA9541_CTL_NMYBUS)
63#define mybus(x) (!((x) & MYBUS) || ((x) & MYBUS) == MYBUS)
64#define busoff(x) (!((x) & BUSON) || ((x) & BUSON) == BUSON)
65
66/* arbitration timeouts, in jiffies */
67#define ARB_TIMEOUT (HZ / 8) /* 125 ms until forcing bus ownership */
68#define ARB2_TIMEOUT (HZ / 4) /* 250 ms until acquisition failure */
69
70/* arbitration retry delays, in us */
71#define SELECT_DELAY_SHORT 50
72#define SELECT_DELAY_LONG 1000
73
74struct pca9541 {
75 struct i2c_client *client;
76 unsigned long select_timeout;
77 unsigned long arb_timeout;
78};
79
80static const struct i2c_device_id pca9541_id[] = {
81 {"pca9541", 0},
82 {}
83};
84
85MODULE_DEVICE_TABLE(i2c, pca9541_id);
86
87#ifdef CONFIG_OF
88static const struct of_device_id pca9541_of_match[] = {
89 { .compatible = "nxp,pca9541" },
90 {}
91};
92MODULE_DEVICE_TABLE(of, pca9541_of_match);
93#endif
94
95/*
96 * Write to chip register. Don't use i2c_transfer()/i2c_smbus_xfer()
97 * as they will try to lock the adapter a second time.
98 */
99static int pca9541_reg_write(struct i2c_client *client, u8 command, u8 val)
100{
101 struct i2c_adapter *adap = client->adapter;
102 union i2c_smbus_data data = { .byte = val };
103
104 return __i2c_smbus_xfer(adap, client->addr, client->flags,
105 I2C_SMBUS_WRITE, command,
106 I2C_SMBUS_BYTE_DATA, &data);
107}
108
109/*
110 * Read from chip register. Don't use i2c_transfer()/i2c_smbus_xfer()
111 * as they will try to lock adapter a second time.
112 */
113static int pca9541_reg_read(struct i2c_client *client, u8 command)
114{
115 struct i2c_adapter *adap = client->adapter;
116 union i2c_smbus_data data;
117 int ret;
118
119 ret = __i2c_smbus_xfer(adap, client->addr, client->flags,
120 I2C_SMBUS_READ, command,
121 I2C_SMBUS_BYTE_DATA, &data);
122
123 return ret ?: data.byte;
124}
125
126/*
127 * Arbitration management functions
128 */
129
130/* Release bus. Also reset NTESTON and BUSINIT if it was set. */
131static void pca9541_release_bus(struct i2c_client *client)
132{
133 int reg;
134
135 reg = pca9541_reg_read(client, PCA9541_CONTROL);
136 if (reg >= 0 && !busoff(reg) && mybus(reg))
137 pca9541_reg_write(client, PCA9541_CONTROL,
138 (reg & PCA9541_CTL_NBUSON) >> 1);
139}
140
141/*
142 * Arbitration is defined as a two-step process. A bus master can only activate
143 * the slave bus if it owns it; otherwise it has to request ownership first.
144 * This multi-step process ensures that access contention is resolved
145 * gracefully.
146 *
147 * Bus Ownership Other master Action
148 * state requested access
149 * ----------------------------------------------------
150 * off - yes wait for arbitration timeout or
151 * for other master to drop request
152 * off no no take ownership
153 * off yes no turn on bus
154 * on yes - done
155 * on no - wait for arbitration timeout or
156 * for other master to release bus
157 *
158 * The main contention point occurs if the slave bus is off and both masters
159 * request ownership at the same time. In this case, one master will turn on
160 * the slave bus, believing that it owns it. The other master will request
161 * bus ownership. Result is that the bus is turned on, and master which did
162 * _not_ own the slave bus before ends up owning it.
163 */
164
165/* Control commands per PCA9541 datasheet */
166static const u8 pca9541_control[16] = {
167 4, 0, 1, 5, 4, 4, 5, 5, 0, 0, 1, 1, 0, 4, 5, 1
168};
169
170/*
171 * Channel arbitration
172 *
173 * Return values:
174 * <0: error
175 * 0 : bus not acquired
176 * 1 : bus acquired
177 */
178static int pca9541_arbitrate(struct i2c_client *client)
179{
180 struct i2c_mux_core *muxc = i2c_get_clientdata(client);
181 struct pca9541 *data = i2c_mux_priv(muxc);
182 int reg;
183
184 reg = pca9541_reg_read(client, PCA9541_CONTROL);
185 if (reg < 0)
186 return reg;
187
188 if (busoff(reg)) {
189 int istat;
190 /*
191 * Bus is off. Request ownership or turn it on unless
192 * other master requested ownership.
193 */
194 istat = pca9541_reg_read(client, PCA9541_ISTAT);
195 if (!(istat & PCA9541_ISTAT_NMYTEST)
196 || time_is_before_eq_jiffies(data->arb_timeout)) {
197 /*
198 * Other master did not request ownership,
199 * or arbitration timeout expired. Take the bus.
200 */
201 pca9541_reg_write(client,
202 PCA9541_CONTROL,
203 pca9541_control[reg & 0x0f]
204 | PCA9541_CTL_NTESTON);
205 data->select_timeout = SELECT_DELAY_SHORT;
206 } else {
207 /*
208 * Other master requested ownership.
209 * Set extra long timeout to give it time to acquire it.
210 */
211 data->select_timeout = SELECT_DELAY_LONG * 2;
212 }
213 } else if (mybus(reg)) {
214 /*
215 * Bus is on, and we own it. We are done with acquisition.
216 * Reset NTESTON and BUSINIT, then return success.
217 */
218 if (reg & (PCA9541_CTL_NTESTON | PCA9541_CTL_BUSINIT))
219 pca9541_reg_write(client,
220 PCA9541_CONTROL,
221 reg & ~(PCA9541_CTL_NTESTON
222 | PCA9541_CTL_BUSINIT));
223 return 1;
224 } else {
225 /*
226 * Other master owns the bus.
227 * If arbitration timeout has expired, force ownership.
228 * Otherwise request it.
229 */
230 data->select_timeout = SELECT_DELAY_LONG;
231 if (time_is_before_eq_jiffies(data->arb_timeout)) {
232 /* Time is up, take the bus and reset it. */
233 pca9541_reg_write(client,
234 PCA9541_CONTROL,
235 pca9541_control[reg & 0x0f]
236 | PCA9541_CTL_BUSINIT
237 | PCA9541_CTL_NTESTON);
238 } else {
239 /* Request bus ownership if needed */
240 if (!(reg & PCA9541_CTL_NTESTON))
241 pca9541_reg_write(client,
242 PCA9541_CONTROL,
243 reg | PCA9541_CTL_NTESTON);
244 }
245 }
246 return 0;
247}
248
249static int pca9541_select_chan(struct i2c_mux_core *muxc, u32 chan)
250{
251 struct pca9541 *data = i2c_mux_priv(muxc);
252 struct i2c_client *client = data->client;
253 int ret;
254 unsigned long timeout = jiffies + ARB2_TIMEOUT;
255 /* give up after this time */
256
257 data->arb_timeout = jiffies + ARB_TIMEOUT;
258 /* force bus ownership after this time */
259
260 do {
261 ret = pca9541_arbitrate(client);
262 if (ret)
263 return ret < 0 ? ret : 0;
264
265 if (data->select_timeout == SELECT_DELAY_SHORT)
266 udelay(data->select_timeout);
267 else
268 msleep(data->select_timeout / 1000);
269 } while (time_is_after_eq_jiffies(timeout));
270
271 return -ETIMEDOUT;
272}
273
274static int pca9541_release_chan(struct i2c_mux_core *muxc, u32 chan)
275{
276 struct pca9541 *data = i2c_mux_priv(muxc);
277 struct i2c_client *client = data->client;
278
279 pca9541_release_bus(client);
280 return 0;
281}
282
283/*
284 * I2C init/probing/exit functions
285 */
286static int pca9541_probe(struct i2c_client *client,
287 const struct i2c_device_id *id)
288{
289 struct i2c_adapter *adap = client->adapter;
290 struct i2c_mux_core *muxc;
291 struct pca9541 *data;
292 int ret;
293
294 if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_BYTE_DATA))
295 return -ENODEV;
296
297 /*
298 * I2C accesses are unprotected here.
299 * We have to lock the I2C segment before releasing the bus.
300 */
301 i2c_lock_bus(adap, I2C_LOCK_SEGMENT);
302 pca9541_release_bus(client);
303 i2c_unlock_bus(adap, I2C_LOCK_SEGMENT);
304
305 /* Create mux adapter */
306
307 muxc = i2c_mux_alloc(adap, &client->dev, 1, sizeof(*data),
308 I2C_MUX_ARBITRATOR,
309 pca9541_select_chan, pca9541_release_chan);
310 if (!muxc)
311 return -ENOMEM;
312
313 data = i2c_mux_priv(muxc);
314 data->client = client;
315
316 i2c_set_clientdata(client, muxc);
317
318 ret = i2c_mux_add_adapter(muxc, 0, 0, 0);
319 if (ret)
320 return ret;
321
322 dev_info(&client->dev, "registered master selector for I2C %s\n",
323 client->name);
324
325 return 0;
326}
327
328static int pca9541_remove(struct i2c_client *client)
329{
330 struct i2c_mux_core *muxc = i2c_get_clientdata(client);
331
332 i2c_mux_del_adapters(muxc);
333 return 0;
334}
335
336static struct i2c_driver pca9541_driver = {
337 .driver = {
338 .name = "pca9541",
339 .of_match_table = of_match_ptr(pca9541_of_match),
340 },
341 .probe = pca9541_probe,
342 .remove = pca9541_remove,
343 .id_table = pca9541_id,
344};
345
346module_i2c_driver(pca9541_driver);
347
348MODULE_AUTHOR("Guenter Roeck <linux@roeck-us.net>");
349MODULE_DESCRIPTION("PCA9541 I2C master selector driver");
350MODULE_LICENSE("GPL v2");
1/*
2 * I2C multiplexer driver for PCA9541 bus master selector
3 *
4 * Copyright (c) 2010 Ericsson AB.
5 *
6 * Author: Guenter Roeck <linux@roeck-us.net>
7 *
8 * Derived from:
9 * pca954x.c
10 *
11 * Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
12 * Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
13 *
14 * This file is licensed under the terms of the GNU General Public
15 * License version 2. This program is licensed "as is" without any
16 * warranty of any kind, whether express or implied.
17 */
18
19#include <linux/delay.h>
20#include <linux/device.h>
21#include <linux/i2c.h>
22#include <linux/i2c-mux.h>
23#include <linux/jiffies.h>
24#include <linux/module.h>
25#include <linux/slab.h>
26
27/*
28 * The PCA9541 is a bus master selector. It supports two I2C masters connected
29 * to a single slave bus.
30 *
31 * Before each bus transaction, a master has to acquire bus ownership. After the
32 * transaction is complete, bus ownership has to be released. This fits well
33 * into the I2C multiplexer framework, which provides select and release
34 * functions for this purpose. For this reason, this driver is modeled as
35 * single-channel I2C bus multiplexer.
36 *
37 * This driver assumes that the two bus masters are controlled by two different
38 * hosts. If a single host controls both masters, platform code has to ensure
39 * that only one of the masters is instantiated at any given time.
40 */
41
42#define PCA9541_CONTROL 0x01
43#define PCA9541_ISTAT 0x02
44
45#define PCA9541_CTL_MYBUS (1 << 0)
46#define PCA9541_CTL_NMYBUS (1 << 1)
47#define PCA9541_CTL_BUSON (1 << 2)
48#define PCA9541_CTL_NBUSON (1 << 3)
49#define PCA9541_CTL_BUSINIT (1 << 4)
50#define PCA9541_CTL_TESTON (1 << 6)
51#define PCA9541_CTL_NTESTON (1 << 7)
52
53#define PCA9541_ISTAT_INTIN (1 << 0)
54#define PCA9541_ISTAT_BUSINIT (1 << 1)
55#define PCA9541_ISTAT_BUSOK (1 << 2)
56#define PCA9541_ISTAT_BUSLOST (1 << 3)
57#define PCA9541_ISTAT_MYTEST (1 << 6)
58#define PCA9541_ISTAT_NMYTEST (1 << 7)
59
60#define BUSON (PCA9541_CTL_BUSON | PCA9541_CTL_NBUSON)
61#define MYBUS (PCA9541_CTL_MYBUS | PCA9541_CTL_NMYBUS)
62#define mybus(x) (!((x) & MYBUS) || ((x) & MYBUS) == MYBUS)
63#define busoff(x) (!((x) & BUSON) || ((x) & BUSON) == BUSON)
64
65/* arbitration timeouts, in jiffies */
66#define ARB_TIMEOUT (HZ / 8) /* 125 ms until forcing bus ownership */
67#define ARB2_TIMEOUT (HZ / 4) /* 250 ms until acquisition failure */
68
69/* arbitration retry delays, in us */
70#define SELECT_DELAY_SHORT 50
71#define SELECT_DELAY_LONG 1000
72
73struct pca9541 {
74 struct i2c_client *client;
75 unsigned long select_timeout;
76 unsigned long arb_timeout;
77};
78
79static const struct i2c_device_id pca9541_id[] = {
80 {"pca9541", 0},
81 {}
82};
83
84MODULE_DEVICE_TABLE(i2c, pca9541_id);
85
86#ifdef CONFIG_OF
87static const struct of_device_id pca9541_of_match[] = {
88 { .compatible = "nxp,pca9541" },
89 {}
90};
91MODULE_DEVICE_TABLE(of, pca9541_of_match);
92#endif
93
94/*
95 * Write to chip register. Don't use i2c_transfer()/i2c_smbus_xfer()
96 * as they will try to lock the adapter a second time.
97 */
98static int pca9541_reg_write(struct i2c_client *client, u8 command, u8 val)
99{
100 struct i2c_adapter *adap = client->adapter;
101 union i2c_smbus_data data = { .byte = val };
102
103 return __i2c_smbus_xfer(adap, client->addr, client->flags,
104 I2C_SMBUS_WRITE, command,
105 I2C_SMBUS_BYTE_DATA, &data);
106}
107
108/*
109 * Read from chip register. Don't use i2c_transfer()/i2c_smbus_xfer()
110 * as they will try to lock adapter a second time.
111 */
112static int pca9541_reg_read(struct i2c_client *client, u8 command)
113{
114 struct i2c_adapter *adap = client->adapter;
115 union i2c_smbus_data data;
116 int ret;
117
118 ret = __i2c_smbus_xfer(adap, client->addr, client->flags,
119 I2C_SMBUS_READ, command,
120 I2C_SMBUS_BYTE_DATA, &data);
121
122 return ret ?: data.byte;
123}
124
125/*
126 * Arbitration management functions
127 */
128
129/* Release bus. Also reset NTESTON and BUSINIT if it was set. */
130static void pca9541_release_bus(struct i2c_client *client)
131{
132 int reg;
133
134 reg = pca9541_reg_read(client, PCA9541_CONTROL);
135 if (reg >= 0 && !busoff(reg) && mybus(reg))
136 pca9541_reg_write(client, PCA9541_CONTROL,
137 (reg & PCA9541_CTL_NBUSON) >> 1);
138}
139
140/*
141 * Arbitration is defined as a two-step process. A bus master can only activate
142 * the slave bus if it owns it; otherwise it has to request ownership first.
143 * This multi-step process ensures that access contention is resolved
144 * gracefully.
145 *
146 * Bus Ownership Other master Action
147 * state requested access
148 * ----------------------------------------------------
149 * off - yes wait for arbitration timeout or
150 * for other master to drop request
151 * off no no take ownership
152 * off yes no turn on bus
153 * on yes - done
154 * on no - wait for arbitration timeout or
155 * for other master to release bus
156 *
157 * The main contention point occurs if the slave bus is off and both masters
158 * request ownership at the same time. In this case, one master will turn on
159 * the slave bus, believing that it owns it. The other master will request
160 * bus ownership. Result is that the bus is turned on, and master which did
161 * _not_ own the slave bus before ends up owning it.
162 */
163
164/* Control commands per PCA9541 datasheet */
165static const u8 pca9541_control[16] = {
166 4, 0, 1, 5, 4, 4, 5, 5, 0, 0, 1, 1, 0, 4, 5, 1
167};
168
169/*
170 * Channel arbitration
171 *
172 * Return values:
173 * <0: error
174 * 0 : bus not acquired
175 * 1 : bus acquired
176 */
177static int pca9541_arbitrate(struct i2c_client *client)
178{
179 struct i2c_mux_core *muxc = i2c_get_clientdata(client);
180 struct pca9541 *data = i2c_mux_priv(muxc);
181 int reg;
182
183 reg = pca9541_reg_read(client, PCA9541_CONTROL);
184 if (reg < 0)
185 return reg;
186
187 if (busoff(reg)) {
188 int istat;
189 /*
190 * Bus is off. Request ownership or turn it on unless
191 * other master requested ownership.
192 */
193 istat = pca9541_reg_read(client, PCA9541_ISTAT);
194 if (!(istat & PCA9541_ISTAT_NMYTEST)
195 || time_is_before_eq_jiffies(data->arb_timeout)) {
196 /*
197 * Other master did not request ownership,
198 * or arbitration timeout expired. Take the bus.
199 */
200 pca9541_reg_write(client,
201 PCA9541_CONTROL,
202 pca9541_control[reg & 0x0f]
203 | PCA9541_CTL_NTESTON);
204 data->select_timeout = SELECT_DELAY_SHORT;
205 } else {
206 /*
207 * Other master requested ownership.
208 * Set extra long timeout to give it time to acquire it.
209 */
210 data->select_timeout = SELECT_DELAY_LONG * 2;
211 }
212 } else if (mybus(reg)) {
213 /*
214 * Bus is on, and we own it. We are done with acquisition.
215 * Reset NTESTON and BUSINIT, then return success.
216 */
217 if (reg & (PCA9541_CTL_NTESTON | PCA9541_CTL_BUSINIT))
218 pca9541_reg_write(client,
219 PCA9541_CONTROL,
220 reg & ~(PCA9541_CTL_NTESTON
221 | PCA9541_CTL_BUSINIT));
222 return 1;
223 } else {
224 /*
225 * Other master owns the bus.
226 * If arbitration timeout has expired, force ownership.
227 * Otherwise request it.
228 */
229 data->select_timeout = SELECT_DELAY_LONG;
230 if (time_is_before_eq_jiffies(data->arb_timeout)) {
231 /* Time is up, take the bus and reset it. */
232 pca9541_reg_write(client,
233 PCA9541_CONTROL,
234 pca9541_control[reg & 0x0f]
235 | PCA9541_CTL_BUSINIT
236 | PCA9541_CTL_NTESTON);
237 } else {
238 /* Request bus ownership if needed */
239 if (!(reg & PCA9541_CTL_NTESTON))
240 pca9541_reg_write(client,
241 PCA9541_CONTROL,
242 reg | PCA9541_CTL_NTESTON);
243 }
244 }
245 return 0;
246}
247
248static int pca9541_select_chan(struct i2c_mux_core *muxc, u32 chan)
249{
250 struct pca9541 *data = i2c_mux_priv(muxc);
251 struct i2c_client *client = data->client;
252 int ret;
253 unsigned long timeout = jiffies + ARB2_TIMEOUT;
254 /* give up after this time */
255
256 data->arb_timeout = jiffies + ARB_TIMEOUT;
257 /* force bus ownership after this time */
258
259 do {
260 ret = pca9541_arbitrate(client);
261 if (ret)
262 return ret < 0 ? ret : 0;
263
264 if (data->select_timeout == SELECT_DELAY_SHORT)
265 udelay(data->select_timeout);
266 else
267 msleep(data->select_timeout / 1000);
268 } while (time_is_after_eq_jiffies(timeout));
269
270 return -ETIMEDOUT;
271}
272
273static int pca9541_release_chan(struct i2c_mux_core *muxc, u32 chan)
274{
275 struct pca9541 *data = i2c_mux_priv(muxc);
276 struct i2c_client *client = data->client;
277
278 pca9541_release_bus(client);
279 return 0;
280}
281
282/*
283 * I2C init/probing/exit functions
284 */
285static int pca9541_probe(struct i2c_client *client,
286 const struct i2c_device_id *id)
287{
288 struct i2c_adapter *adap = client->adapter;
289 struct i2c_mux_core *muxc;
290 struct pca9541 *data;
291 int ret;
292
293 if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_BYTE_DATA))
294 return -ENODEV;
295
296 /*
297 * I2C accesses are unprotected here.
298 * We have to lock the I2C segment before releasing the bus.
299 */
300 i2c_lock_bus(adap, I2C_LOCK_SEGMENT);
301 pca9541_release_bus(client);
302 i2c_unlock_bus(adap, I2C_LOCK_SEGMENT);
303
304 /* Create mux adapter */
305
306 muxc = i2c_mux_alloc(adap, &client->dev, 1, sizeof(*data),
307 I2C_MUX_ARBITRATOR,
308 pca9541_select_chan, pca9541_release_chan);
309 if (!muxc)
310 return -ENOMEM;
311
312 data = i2c_mux_priv(muxc);
313 data->client = client;
314
315 i2c_set_clientdata(client, muxc);
316
317 ret = i2c_mux_add_adapter(muxc, 0, 0, 0);
318 if (ret)
319 return ret;
320
321 dev_info(&client->dev, "registered master selector for I2C %s\n",
322 client->name);
323
324 return 0;
325}
326
327static int pca9541_remove(struct i2c_client *client)
328{
329 struct i2c_mux_core *muxc = i2c_get_clientdata(client);
330
331 i2c_mux_del_adapters(muxc);
332 return 0;
333}
334
335static struct i2c_driver pca9541_driver = {
336 .driver = {
337 .name = "pca9541",
338 .of_match_table = of_match_ptr(pca9541_of_match),
339 },
340 .probe = pca9541_probe,
341 .remove = pca9541_remove,
342 .id_table = pca9541_id,
343};
344
345module_i2c_driver(pca9541_driver);
346
347MODULE_AUTHOR("Guenter Roeck <linux@roeck-us.net>");
348MODULE_DESCRIPTION("PCA9541 I2C master selector driver");
349MODULE_LICENSE("GPL v2");