216 lines
6.1 KiB
C
216 lines
6.1 KiB
C
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/*
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* ads7871 - driver for TI ADS7871 A/D converter
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*
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* Copyright (c) 2010 Paul Thomas <pthomas8589@gmail.com>
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 or
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* later as publishhed by the Free Software Foundation.
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*
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* You need to have something like this in struct spi_board_info
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* {
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* .modalias = "ads7871",
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* .max_speed_hz = 2*1000*1000,
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* .chip_select = 0,
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* .bus_num = 1,
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* },
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*/
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/*From figure 18 in the datasheet*/
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/*Register addresses*/
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#define REG_LS_BYTE 0 /*A/D Output Data, LS Byte*/
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#define REG_MS_BYTE 1 /*A/D Output Data, MS Byte*/
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#define REG_PGA_VALID 2 /*PGA Valid Register*/
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#define REG_AD_CONTROL 3 /*A/D Control Register*/
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#define REG_GAIN_MUX 4 /*Gain/Mux Register*/
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#define REG_IO_STATE 5 /*Digital I/O State Register*/
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#define REG_IO_CONTROL 6 /*Digital I/O Control Register*/
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#define REG_OSC_CONTROL 7 /*Rev/Oscillator Control Register*/
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#define REG_SER_CONTROL 24 /*Serial Interface Control Register*/
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#define REG_ID 31 /*ID Register*/
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/*
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* From figure 17 in the datasheet
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* These bits get ORed with the address to form
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* the instruction byte
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*/
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/*Instruction Bit masks*/
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#define INST_MODE_BM (1 << 7)
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#define INST_READ_BM (1 << 6)
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#define INST_16BIT_BM (1 << 5)
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/*From figure 18 in the datasheet*/
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/*bit masks for Rev/Oscillator Control Register*/
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#define MUX_CNV_BV 7
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#define MUX_CNV_BM (1 << MUX_CNV_BV)
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#define MUX_M3_BM (1 << 3) /*M3 selects single ended*/
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#define MUX_G_BV 4 /*allows for reg = (gain << MUX_G_BV) | ...*/
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/*From figure 18 in the datasheet*/
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/*bit masks for Rev/Oscillator Control Register*/
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#define OSC_OSCR_BM (1 << 5)
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#define OSC_OSCE_BM (1 << 4)
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#define OSC_REFE_BM (1 << 3)
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#define OSC_BUFE_BM (1 << 2)
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#define OSC_R2V_BM (1 << 1)
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#define OSC_RBG_BM (1 << 0)
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/spi/spi.h>
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#include <linux/hwmon.h>
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#include <linux/hwmon-sysfs.h>
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#include <linux/err.h>
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#include <linux/delay.h>
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#define DEVICE_NAME "ads7871"
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struct ads7871_data {
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struct spi_device *spi;
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};
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static int ads7871_read_reg8(struct spi_device *spi, int reg)
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{
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int ret;
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reg = reg | INST_READ_BM;
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ret = spi_w8r8(spi, reg);
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return ret;
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}
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static int ads7871_read_reg16(struct spi_device *spi, int reg)
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{
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int ret;
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reg = reg | INST_READ_BM | INST_16BIT_BM;
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ret = spi_w8r16(spi, reg);
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return ret;
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}
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static int ads7871_write_reg8(struct spi_device *spi, int reg, u8 val)
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{
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u8 tmp[2] = {reg, val};
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return spi_write(spi, tmp, sizeof(tmp));
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}
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static ssize_t show_voltage(struct device *dev,
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struct device_attribute *da, char *buf)
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{
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struct ads7871_data *pdata = dev_get_drvdata(dev);
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struct spi_device *spi = pdata->spi;
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struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
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int ret, val, i = 0;
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uint8_t channel, mux_cnv;
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channel = attr->index;
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/*
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* TODO: add support for conversions
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* other than single ended with a gain of 1
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*/
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/*MUX_M3_BM forces single ended*/
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/*This is also where the gain of the PGA would be set*/
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ads7871_write_reg8(spi, REG_GAIN_MUX,
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(MUX_CNV_BM | MUX_M3_BM | channel));
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ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
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mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV);
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/*
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* on 400MHz arm9 platform the conversion
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* is already done when we do this test
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*/
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while ((i < 2) && mux_cnv) {
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i++;
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ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
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mux_cnv = ((ret & MUX_CNV_BM) >> MUX_CNV_BV);
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msleep_interruptible(1);
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}
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if (mux_cnv == 0) {
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val = ads7871_read_reg16(spi, REG_LS_BYTE);
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/*result in volts*10000 = (val/8192)*2.5*10000*/
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val = ((val >> 2) * 25000) / 8192;
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return sprintf(buf, "%d\n", val);
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} else {
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return -1;
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}
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}
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static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, show_voltage, NULL, 0);
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static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, show_voltage, NULL, 1);
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static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, show_voltage, NULL, 2);
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static SENSOR_DEVICE_ATTR(in3_input, S_IRUGO, show_voltage, NULL, 3);
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static SENSOR_DEVICE_ATTR(in4_input, S_IRUGO, show_voltage, NULL, 4);
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static SENSOR_DEVICE_ATTR(in5_input, S_IRUGO, show_voltage, NULL, 5);
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static SENSOR_DEVICE_ATTR(in6_input, S_IRUGO, show_voltage, NULL, 6);
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static SENSOR_DEVICE_ATTR(in7_input, S_IRUGO, show_voltage, NULL, 7);
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static struct attribute *ads7871_attrs[] = {
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&sensor_dev_attr_in0_input.dev_attr.attr,
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&sensor_dev_attr_in1_input.dev_attr.attr,
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&sensor_dev_attr_in2_input.dev_attr.attr,
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&sensor_dev_attr_in3_input.dev_attr.attr,
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&sensor_dev_attr_in4_input.dev_attr.attr,
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&sensor_dev_attr_in5_input.dev_attr.attr,
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&sensor_dev_attr_in6_input.dev_attr.attr,
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&sensor_dev_attr_in7_input.dev_attr.attr,
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NULL
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};
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ATTRIBUTE_GROUPS(ads7871);
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static int ads7871_probe(struct spi_device *spi)
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{
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struct device *dev = &spi->dev;
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int ret;
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uint8_t val;
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struct ads7871_data *pdata;
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struct device *hwmon_dev;
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/* Configure the SPI bus */
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spi->mode = (SPI_MODE_0);
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spi->bits_per_word = 8;
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spi_setup(spi);
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ads7871_write_reg8(spi, REG_SER_CONTROL, 0);
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ads7871_write_reg8(spi, REG_AD_CONTROL, 0);
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val = (OSC_OSCR_BM | OSC_OSCE_BM | OSC_REFE_BM | OSC_BUFE_BM);
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ads7871_write_reg8(spi, REG_OSC_CONTROL, val);
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ret = ads7871_read_reg8(spi, REG_OSC_CONTROL);
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dev_dbg(dev, "REG_OSC_CONTROL write:%x, read:%x\n", val, ret);
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/*
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* because there is no other error checking on an SPI bus
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* we need to make sure we really have a chip
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*/
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if (val != ret)
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return -ENODEV;
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pdata = devm_kzalloc(dev, sizeof(struct ads7871_data), GFP_KERNEL);
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if (!pdata)
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return -ENOMEM;
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pdata->spi = spi;
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hwmon_dev = devm_hwmon_device_register_with_groups(dev, spi->modalias,
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pdata,
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ads7871_groups);
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return PTR_ERR_OR_ZERO(hwmon_dev);
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}
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static struct spi_driver ads7871_driver = {
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.driver = {
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.name = DEVICE_NAME,
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},
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.probe = ads7871_probe,
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};
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module_spi_driver(ads7871_driver);
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MODULE_AUTHOR("Paul Thomas <pthomas8589@gmail.com>");
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MODULE_DESCRIPTION("TI ADS7871 A/D driver");
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MODULE_LICENSE("GPL");
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