drivers/rtc/rtc-max6902.c

Source file repositories/reference/linux-study-clean/drivers/rtc/rtc-max6902.c

File Facts

System
Linux kernel
Corpus path
drivers/rtc/rtc-max6902.c
Extension
.c
Size
3807 bytes
Lines
155
Domain
Driver Families
Bucket
drivers/rtc
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
/* drivers/rtc/rtc-max6902.c
 *
 * Copyright (C) 2006 8D Technologies inc.
 * Copyright (C) 2004 Compulab Ltd.
 *
 * Driver for MAX6902 spi RTC
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/init.h>
#include <linux/rtc.h>
#include <linux/spi/spi.h>
#include <linux/bcd.h>

#define MAX6902_REG_SECONDS		0x01
#define MAX6902_REG_MINUTES		0x03
#define MAX6902_REG_HOURS		0x05
#define MAX6902_REG_DATE		0x07
#define MAX6902_REG_MONTH		0x09
#define MAX6902_REG_DAY			0x0B
#define MAX6902_REG_YEAR		0x0D
#define MAX6902_REG_CONTROL		0x0F
#define MAX6902_REG_CENTURY		0x13

static int max6902_set_reg(struct device *dev, unsigned char address,
				unsigned char data)
{
	struct spi_device *spi = to_spi_device(dev);
	unsigned char buf[2];

	/* MSB must be '0' to write */
	buf[0] = address & 0x7f;
	buf[1] = data;

	return spi_write_then_read(spi, buf, 2, NULL, 0);
}

static int max6902_get_reg(struct device *dev, unsigned char address,
				unsigned char *data)
{
	struct spi_device *spi = to_spi_device(dev);

	/* Set MSB to indicate read */
	*data = address | 0x80;

	return spi_write_then_read(spi, data, 1, data, 1);
}

static int max6902_read_time(struct device *dev, struct rtc_time *dt)
{
	int err, century;
	struct spi_device *spi = to_spi_device(dev);
	unsigned char buf[8];

	buf[0] = 0xbf;	/* Burst read */

	err = spi_write_then_read(spi, buf, 1, buf, 8);
	if (err != 0)
		return err;

	/* The chip sends data in this order:
	 * Seconds, Minutes, Hours, Date, Month, Day, Year */
	dt->tm_sec	= bcd2bin(buf[0]);
	dt->tm_min	= bcd2bin(buf[1]);
	dt->tm_hour	= bcd2bin(buf[2]);
	dt->tm_mday	= bcd2bin(buf[3]);
	dt->tm_mon	= bcd2bin(buf[4]) - 1;
	dt->tm_wday	= bcd2bin(buf[5]);
	dt->tm_year	= bcd2bin(buf[6]);

	/* Read century */
	err = max6902_get_reg(dev, MAX6902_REG_CENTURY, &buf[0]);
	if (err != 0)
		return err;

	century = bcd2bin(buf[0]) * 100;

	dt->tm_year += century;
	dt->tm_year -= 1900;

	return 0;
}

static int max6902_set_time(struct device *dev, struct rtc_time *dt)
{
	dt->tm_year = dt->tm_year + 1900;

Annotation

Implementation Notes