drivers/misc/ds1682.c

Source file repositories/reference/linux-study-clean/drivers/misc/ds1682.c

File Facts

System
Linux kernel
Corpus path
drivers/misc/ds1682.c
Extension
.c
Size
8039 bytes
Lines
300
Domain
Driver Families
Bucket
drivers/misc
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Dallas Semiconductor DS1682 Elapsed Time Recorder device driver
 *
 * Written by: Grant Likely <grant.likely@secretlab.ca>
 *
 * Copyright (C) 2007 Secret Lab Technologies Ltd.
 */

/*
 * The DS1682 elapsed timer recorder is a simple device that implements
 * one elapsed time counter, one event counter, an alarm signal and 10
 * bytes of general purpose EEPROM.
 *
 * This driver provides access to the DS1682 counters and user data via
 * the sysfs.  The following attributes are added to the device node:
 *     elapsed_time (u32): Total elapsed event time in ms resolution
 *     alarm_time (u32): When elapsed time exceeds the value in alarm_time,
 *                       then the alarm pin is asserted.
 *     event_count (u16): number of times the event pin has gone low.
 *     eeprom (u8[10]): general purpose EEPROM
 *
 * Counter registers and user data are both read/write unless the device
 * has been write protected.  This driver does not support turning off write
 * protection.  Once write protection is turned on, it is impossible to
 * turn it off again, so I have left the feature out of this driver to avoid
 * accidental enabling, but it is trivial to add write protect support.
 *
 */

#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/string.h>
#include <linux/list.h>
#include <linux/nvmem-provider.h>
#include <linux/sysfs.h>
#include <linux/ctype.h>
#include <linux/hwmon-sysfs.h>

/* Device registers */
#define DS1682_REG_CONFIG		0x00
#define DS1682_REG_ALARM		0x01
#define DS1682_REG_ELAPSED		0x05
#define DS1682_REG_EVT_CNTR		0x09
#define DS1682_REG_EEPROM		0x0b
#define DS1682_REG_RESET		0x1d
#define DS1682_REG_WRITE_DISABLE	0x1e
#define DS1682_REG_WRITE_MEM_DISABLE	0x1f

#define DS1682_EEPROM_SIZE		10

/*
 * Generic counter attributes
 */
static ssize_t ds1682_show(struct device *dev, struct device_attribute *attr,
			   char *buf)
{
	struct sensor_device_attribute_2 *sattr = to_sensor_dev_attr_2(attr);
	struct i2c_client *client = to_i2c_client(dev);
	unsigned long long val, check;
	__le32 val_le = 0;
	int rc;

	dev_dbg(dev, "ds1682_show() called on %s\n", attr->attr.name);

	/* Read the register */
	rc = i2c_smbus_read_i2c_block_data(client, sattr->index, sattr->nr,
					   (u8 *)&val_le);
	if (rc < 0)
		return -EIO;

	val = le32_to_cpu(val_le);

	if (sattr->index == DS1682_REG_ELAPSED) {
		int retries = 5;

		/* Detect and retry when a tick occurs mid-read */
		do {
			rc = i2c_smbus_read_i2c_block_data(client, sattr->index,
							   sattr->nr,
							   (u8 *)&val_le);
			if (rc < 0 || retries <= 0)
				return -EIO;

			check = val;
			val = le32_to_cpu(val_le);
			retries--;
		} while (val != check && val != (check + 1));
	}

Annotation

Implementation Notes