252 lines
6.4 KiB
C
252 lines
6.4 KiB
C
/*
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* rtc class driver for the Maxim MAX6900 chip
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*
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* Author: Dale Farnsworth <dale@farnsworth.org>
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*
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* based on previously existing rtc class drivers
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*
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* 2007 (c) MontaVista, Software, Inc. This file is licensed under
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* the terms of the GNU General Public License version 2. This program
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* is licensed "as is" without any warranty of any kind, whether express
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* or implied.
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*/
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#include <linux/module.h>
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#include <linux/i2c.h>
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#include <linux/bcd.h>
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#include <linux/rtc.h>
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#include <linux/delay.h>
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#define DRV_VERSION "0.2"
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/*
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* register indices
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*/
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#define MAX6900_REG_SC 0 /* seconds 00-59 */
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#define MAX6900_REG_MN 1 /* minutes 00-59 */
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#define MAX6900_REG_HR 2 /* hours 00-23 */
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#define MAX6900_REG_DT 3 /* day of month 00-31 */
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#define MAX6900_REG_MO 4 /* month 01-12 */
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#define MAX6900_REG_DW 5 /* day of week 1-7 */
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#define MAX6900_REG_YR 6 /* year 00-99 */
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#define MAX6900_REG_CT 7 /* control */
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/* register 8 is undocumented */
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#define MAX6900_REG_CENTURY 9 /* century */
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#define MAX6900_REG_LEN 10
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#define MAX6900_BURST_LEN 8 /* can burst r/w first 8 regs */
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#define MAX6900_REG_CT_WP (1 << 7) /* Write Protect */
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/*
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* register read/write commands
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*/
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#define MAX6900_REG_CONTROL_WRITE 0x8e
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#define MAX6900_REG_CENTURY_WRITE 0x92
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#define MAX6900_REG_CENTURY_READ 0x93
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#define MAX6900_REG_RESERVED_READ 0x96
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#define MAX6900_REG_BURST_WRITE 0xbe
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#define MAX6900_REG_BURST_READ 0xbf
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#define MAX6900_IDLE_TIME_AFTER_WRITE 3 /* specification says 2.5 mS */
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static struct i2c_driver max6900_driver;
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static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
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{
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u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ };
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u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ };
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struct i2c_msg msgs[4] = {
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{
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.addr = client->addr,
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.flags = 0, /* write */
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.len = sizeof(reg_burst_read),
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.buf = reg_burst_read}
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,
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{
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.addr = client->addr,
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.flags = I2C_M_RD,
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.len = MAX6900_BURST_LEN,
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.buf = buf}
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,
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{
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.addr = client->addr,
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.flags = 0, /* write */
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.len = sizeof(reg_century_read),
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.buf = reg_century_read}
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,
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{
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.addr = client->addr,
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.flags = I2C_M_RD,
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.len = sizeof(buf[MAX6900_REG_CENTURY]),
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.buf = &buf[MAX6900_REG_CENTURY]
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}
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};
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int rc;
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rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
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if (rc != ARRAY_SIZE(msgs)) {
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dev_err(&client->dev, "%s: register read failed\n", __func__);
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return -EIO;
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}
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return 0;
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}
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static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf)
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{
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u8 i2c_century_buf[1 + 1] = { MAX6900_REG_CENTURY_WRITE };
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struct i2c_msg century_msgs[1] = {
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{
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.addr = client->addr,
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.flags = 0, /* write */
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.len = sizeof(i2c_century_buf),
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.buf = i2c_century_buf}
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};
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u8 i2c_burst_buf[MAX6900_BURST_LEN + 1] = { MAX6900_REG_BURST_WRITE };
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struct i2c_msg burst_msgs[1] = {
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{
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.addr = client->addr,
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.flags = 0, /* write */
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.len = sizeof(i2c_burst_buf),
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.buf = i2c_burst_buf}
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};
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int rc;
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/*
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* We have to make separate calls to i2c_transfer because of
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* the need to delay after each write to the chip. Also,
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* we write the century byte first, since we set the write-protect
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* bit as part of the burst write.
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*/
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i2c_century_buf[1] = buf[MAX6900_REG_CENTURY];
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rc = i2c_transfer(client->adapter, century_msgs,
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ARRAY_SIZE(century_msgs));
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if (rc != ARRAY_SIZE(century_msgs))
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goto write_failed;
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msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
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memcpy(&i2c_burst_buf[1], buf, MAX6900_BURST_LEN);
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rc = i2c_transfer(client->adapter, burst_msgs, ARRAY_SIZE(burst_msgs));
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if (rc != ARRAY_SIZE(burst_msgs))
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goto write_failed;
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msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
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return 0;
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write_failed:
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dev_err(&client->dev, "%s: register write failed\n", __func__);
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return -EIO;
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}
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static int max6900_i2c_read_time(struct i2c_client *client, struct rtc_time *tm)
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{
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int rc;
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u8 regs[MAX6900_REG_LEN];
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rc = max6900_i2c_read_regs(client, regs);
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if (rc < 0)
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return rc;
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tm->tm_sec = bcd2bin(regs[MAX6900_REG_SC]);
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tm->tm_min = bcd2bin(regs[MAX6900_REG_MN]);
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tm->tm_hour = bcd2bin(regs[MAX6900_REG_HR] & 0x3f);
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tm->tm_mday = bcd2bin(regs[MAX6900_REG_DT]);
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tm->tm_mon = bcd2bin(regs[MAX6900_REG_MO]) - 1;
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tm->tm_year = bcd2bin(regs[MAX6900_REG_YR]) +
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bcd2bin(regs[MAX6900_REG_CENTURY]) * 100 - 1900;
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tm->tm_wday = bcd2bin(regs[MAX6900_REG_DW]);
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return rtc_valid_tm(tm);
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}
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static int max6900_i2c_clear_write_protect(struct i2c_client *client)
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{
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return i2c_smbus_write_byte_data(client, MAX6900_REG_CONTROL_WRITE, 0);
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}
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static int
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max6900_i2c_set_time(struct i2c_client *client, struct rtc_time const *tm)
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{
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u8 regs[MAX6900_REG_LEN];
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int rc;
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rc = max6900_i2c_clear_write_protect(client);
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if (rc < 0)
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return rc;
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regs[MAX6900_REG_SC] = bin2bcd(tm->tm_sec);
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regs[MAX6900_REG_MN] = bin2bcd(tm->tm_min);
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regs[MAX6900_REG_HR] = bin2bcd(tm->tm_hour);
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regs[MAX6900_REG_DT] = bin2bcd(tm->tm_mday);
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regs[MAX6900_REG_MO] = bin2bcd(tm->tm_mon + 1);
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regs[MAX6900_REG_DW] = bin2bcd(tm->tm_wday);
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regs[MAX6900_REG_YR] = bin2bcd(tm->tm_year % 100);
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regs[MAX6900_REG_CENTURY] = bin2bcd((tm->tm_year + 1900) / 100);
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/* set write protect */
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regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP;
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rc = max6900_i2c_write_regs(client, regs);
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if (rc < 0)
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return rc;
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return 0;
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}
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static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm)
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{
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return max6900_i2c_read_time(to_i2c_client(dev), tm);
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}
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static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm)
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{
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return max6900_i2c_set_time(to_i2c_client(dev), tm);
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}
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static const struct rtc_class_ops max6900_rtc_ops = {
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.read_time = max6900_rtc_read_time,
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.set_time = max6900_rtc_set_time,
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};
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static int
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max6900_probe(struct i2c_client *client, const struct i2c_device_id *id)
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{
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struct rtc_device *rtc;
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if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
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return -ENODEV;
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dev_info(&client->dev, "chip found, driver version " DRV_VERSION "\n");
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rtc = devm_rtc_device_register(&client->dev, max6900_driver.driver.name,
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&max6900_rtc_ops, THIS_MODULE);
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if (IS_ERR(rtc))
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return PTR_ERR(rtc);
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i2c_set_clientdata(client, rtc);
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return 0;
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}
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static struct i2c_device_id max6900_id[] = {
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{ "max6900", 0 },
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{ }
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};
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static struct i2c_driver max6900_driver = {
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.driver = {
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.name = "rtc-max6900",
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},
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.probe = max6900_probe,
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.id_table = max6900_id,
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};
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module_i2c_driver(max6900_driver);
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MODULE_DESCRIPTION("Maxim MAX6900 RTC driver");
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MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>");
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MODULE_LICENSE("GPL");
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MODULE_VERSION(DRV_VERSION);
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