drivers/rtc/rtc-max6900.c

Source file repositories/reference/linux-study-clean/drivers/rtc/rtc-max6900.c

File Facts

System
Linux kernel
Corpus path
drivers/rtc/rtc-max6900.c
Extension
.c
Size
6125 bytes
Lines
236
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
/*
 * rtc class driver for the Maxim MAX6900 chip
 *
 * Copyright (c) 2007 MontaVista, Software, Inc.
 *
 * Author: Dale Farnsworth <dale@farnsworth.org>
 *
 * based on previously existing rtc class drivers
 */

#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/bcd.h>
#include <linux/rtc.h>
#include <linux/delay.h>

/*
 * register indices
 */
#define MAX6900_REG_SC			0	/* seconds      00-59 */
#define MAX6900_REG_MN			1	/* minutes      00-59 */
#define MAX6900_REG_HR			2	/* hours        00-23 */
#define MAX6900_REG_DT			3	/* day of month 00-31 */
#define MAX6900_REG_MO			4	/* month        01-12 */
#define MAX6900_REG_DW			5	/* day of week   1-7  */
#define MAX6900_REG_YR			6	/* year         00-99 */
#define MAX6900_REG_CT			7	/* control */
						/* register 8 is undocumented */
#define MAX6900_REG_CENTURY		9	/* century */
#define MAX6900_REG_LEN			10

#define MAX6900_BURST_LEN		8	/* can burst r/w first 8 regs */

#define MAX6900_REG_CT_WP		(1 << 7)	/* Write Protect */

/*
 * register read/write commands
 */
#define MAX6900_REG_CONTROL_WRITE	0x8e
#define MAX6900_REG_CENTURY_WRITE	0x92
#define MAX6900_REG_CENTURY_READ	0x93
#define MAX6900_REG_RESERVED_READ	0x96
#define MAX6900_REG_BURST_WRITE		0xbe
#define MAX6900_REG_BURST_READ		0xbf

#define MAX6900_IDLE_TIME_AFTER_WRITE	3	/* specification says 2.5 mS */

static struct i2c_driver max6900_driver;

static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
{
	u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ };
	u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ };
	struct i2c_msg msgs[4] = {
		{
		 .addr = client->addr,
		 .flags = 0,	/* write */
		 .len = sizeof(reg_burst_read),
		 .buf = reg_burst_read}
		,
		{
		 .addr = client->addr,
		 .flags = I2C_M_RD,
		 .len = MAX6900_BURST_LEN,
		 .buf = buf}
		,
		{
		 .addr = client->addr,
		 .flags = 0,	/* write */
		 .len = sizeof(reg_century_read),
		 .buf = reg_century_read}
		,
		{
		 .addr = client->addr,
		 .flags = I2C_M_RD,
		 .len = sizeof(buf[MAX6900_REG_CENTURY]),
		 .buf = &buf[MAX6900_REG_CENTURY]
		 }
	};
	int rc;

	rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
	if (rc != ARRAY_SIZE(msgs)) {
		dev_err(&client->dev, "%s: register read failed\n", __func__);
		return -EIO;
	}
	return 0;
}

Annotation

Implementation Notes