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235 lines
6.0 KiB
235 lines
6.0 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* rtc class driver for the Maxim MAX6900 chip |
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* |
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* Copyright (c) 2007 MontaVista, Software, Inc. |
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* |
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* Author: Dale Farnsworth <[email protected]> |
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* |
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* based on previously existing rtc class drivers |
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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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/* |
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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_rtc_read_time(struct device *dev, struct rtc_time *tm) |
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{ |
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struct i2c_client *client = to_i2c_client(dev); |
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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 0; |
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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 max6900_rtc_set_time(struct device *dev, struct rtc_time *tm) |
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{ |
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struct i2c_client *client = to_i2c_client(dev); |
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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 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 max6900_probe(struct i2c_client *client) |
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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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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 const struct i2c_device_id max6900_id[] = { |
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{ "max6900", 0 }, |
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{ } |
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}; |
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MODULE_DEVICE_TABLE(i2c, max6900_id); |
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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_new = 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 <[email protected]>"); |
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MODULE_LICENSE("GPL");
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