linux-imx

/*

 * adcxx.c

 *

 * The adcxx4s is an AD converter family from National Semiconductor (NS).

 *

 * Copyright (c) 2008 Marc Pignat <marc.pignat@hevs.ch>

 *

 * The adcxx4s communicates with a host processor via an SPI/Microwire Bus

 * interface. This driver supports the whole family of devices with name

 * ADC<bb><c>S<sss>, where

 * * bb is the resolution in number of bits (8, 10, 12)

 * * c is the number of channels (1, 2, 4, 8)

 * * sss is the maximum conversion speed (021 for 200 kSPS, 051 for 500 kSPS

 *   and 101 for 1 MSPS)

 *

 * Complete datasheets are available at National's website here:

 * http://www.national.com/ds/DC/ADC<bb><c>S<sss>.pdf

 *

 * Handling of 8, 10 and 12 bits converters are the same, the

 * unavailable bits are 0 :)

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation; either version 2 of the License, or

 * (at your option) any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

 */

​

#include <linux/init.h>

#include <linux/module.h>

#include <linux/kernel.h>

#include <linux/slab.h>

#include <linux/device.h>

#include <linux/err.h>

#include <linux/sysfs.h>

#include <linux/hwmon.h>

#include <linux/hwmon-sysfs.h>

#include <linux/mutex.h>

#include <linux/mod_devicetable.h>

#include <linux/spi/spi.h>

​

#define DRVNAME     "adcxx"

​

struct adcxx {

    struct device *hwmon_dev;

    struct mutex lock;

    u32 channels;

    u32 reference; /* in millivolts */

};

​

/* sysfs hook function */

static ssize_t adcxx_show(struct device *dev,

              struct device_attribute *devattr, char *buf)

{

    struct spi_device *spi = to_spi_device(dev);

    struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);

    struct adcxx *adc = spi_get_drvdata(spi);

    u8 tx_buf[2];

    u8 rx_buf[2];

    int status;

    u32 value;

​

    if (mutex_lock_interruptible(&adc->lock))

        return -ERESTARTSYS;

​

    if (adc->channels == 1) {

        status = spi_read(spi, rx_buf, sizeof(rx_buf));

    } else {

        tx_buf[0] = attr->index << 3; /* other bits are don't care */

        status = spi_write_then_read(spi, tx_buf, sizeof(tx_buf),

                        rx_buf, sizeof(rx_buf));

    }

    if (status < 0) {

        dev_warn(dev, "SPI synch. transfer failed with status %d\n",

                status);

        goto out;

    }

​

    value = (rx_buf[0] << 8) + rx_buf[1];

    dev_dbg(dev, "raw value = 0x%x\n", value);

​

    value = value * adc->reference >> 12;

    status = sprintf(buf, "%d\n", value);

out: