linux/drivers/rtc/rtc-ds1672.c
Colin Ian King f0c04c2767 rtc: ds1672: fix unintended sign extension
Shifting a u8 by 24 will cause the value to be promoted to an integer. If
the top bit of the u8 is set then the following conversion to an unsigned
long will sign extend the value causing the upper 32 bits to be set in
the result.

Fix this by casting the u8 value to an unsigned long before the shift.

Detected by CoverityScan, CID#138801 ("Unintended sign extension")

Fixes: edf1aaa31f ("[PATCH] RTC subsystem: DS1672 driver")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
2019-02-05 23:11:31 +01:00

220 lines
5.1 KiB
C

/*
* An rtc/i2c driver for the Dallas DS1672
* Copyright 2005-06 Tower Technologies
*
* Author: Alessandro Zummo <a.zummo@towertech.it>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/i2c.h>
#include <linux/rtc.h>
#include <linux/module.h>
/* Registers */
#define DS1672_REG_CNT_BASE 0
#define DS1672_REG_CONTROL 4
#define DS1672_REG_TRICKLE 5
#define DS1672_REG_CONTROL_EOSC 0x80
static struct i2c_driver ds1672_driver;
/*
* In the routines that deal directly with the ds1672 hardware, we use
* rtc_time -- month 0-11, hour 0-23, yr = calendar year-epoch
* Epoch is initialized as 2000. Time is set to UTC.
*/
static int ds1672_get_datetime(struct i2c_client *client, struct rtc_time *tm)
{
unsigned long time;
unsigned char addr = DS1672_REG_CNT_BASE;
unsigned char buf[4];
struct i2c_msg msgs[] = {
{/* setup read ptr */
.addr = client->addr,
.len = 1,
.buf = &addr
},
{/* read date */
.addr = client->addr,
.flags = I2C_M_RD,
.len = 4,
.buf = buf
},
};
/* read date registers */
if ((i2c_transfer(client->adapter, &msgs[0], 2)) != 2) {
dev_err(&client->dev, "%s: read error\n", __func__);
return -EIO;
}
dev_dbg(&client->dev,
"%s: raw read data - counters=%02x,%02x,%02x,%02x\n",
__func__, buf[0], buf[1], buf[2], buf[3]);
time = ((unsigned long)buf[3] << 24) | (buf[2] << 16) |
(buf[1] << 8) | buf[0];
rtc_time_to_tm(time, tm);
dev_dbg(&client->dev, "%s: tm is secs=%d, mins=%d, hours=%d, "
"mday=%d, mon=%d, year=%d, wday=%d\n",
__func__, tm->tm_sec, tm->tm_min, tm->tm_hour,
tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);
return 0;
}
static int ds1672_set_mmss(struct i2c_client *client, unsigned long secs)
{
int xfer;
unsigned char buf[6];
buf[0] = DS1672_REG_CNT_BASE;
buf[1] = secs & 0x000000FF;
buf[2] = (secs & 0x0000FF00) >> 8;
buf[3] = (secs & 0x00FF0000) >> 16;
buf[4] = (secs & 0xFF000000) >> 24;
buf[5] = 0; /* set control reg to enable counting */
xfer = i2c_master_send(client, buf, 6);
if (xfer != 6) {
dev_err(&client->dev, "%s: send: %d\n", __func__, xfer);
return -EIO;
}
return 0;
}
static int ds1672_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
return ds1672_get_datetime(to_i2c_client(dev), tm);
}
static int ds1672_rtc_set_mmss(struct device *dev, unsigned long secs)
{
return ds1672_set_mmss(to_i2c_client(dev), secs);
}
static int ds1672_get_control(struct i2c_client *client, u8 *status)
{
unsigned char addr = DS1672_REG_CONTROL;
struct i2c_msg msgs[] = {
{/* setup read ptr */
.addr = client->addr,
.len = 1,
.buf = &addr
},
{/* read control */
.addr = client->addr,
.flags = I2C_M_RD,
.len = 1,
.buf = status
},
};
/* read control register */
if ((i2c_transfer(client->adapter, &msgs[0], 2)) != 2) {
dev_err(&client->dev, "%s: read error\n", __func__);
return -EIO;
}
return 0;
}
/* following are the sysfs callback functions */
static ssize_t show_control(struct device *dev, struct device_attribute *attr,
char *buf)
{
struct i2c_client *client = to_i2c_client(dev);
u8 control;
int err;
err = ds1672_get_control(client, &control);
if (err)
return err;
return sprintf(buf, "%s\n", (control & DS1672_REG_CONTROL_EOSC)
? "disabled" : "enabled");
}
static DEVICE_ATTR(control, S_IRUGO, show_control, NULL);
static const struct rtc_class_ops ds1672_rtc_ops = {
.read_time = ds1672_rtc_read_time,
.set_mmss = ds1672_rtc_set_mmss,
};
static int ds1672_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
int err = 0;
u8 control;
struct rtc_device *rtc;
dev_dbg(&client->dev, "%s\n", __func__);
if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
return -ENODEV;
rtc = devm_rtc_device_register(&client->dev, ds1672_driver.driver.name,
&ds1672_rtc_ops, THIS_MODULE);
if (IS_ERR(rtc))
return PTR_ERR(rtc);
i2c_set_clientdata(client, rtc);
/* read control register */
err = ds1672_get_control(client, &control);
if (err) {
dev_warn(&client->dev, "Unable to read the control register\n");
}
if (control & DS1672_REG_CONTROL_EOSC)
dev_warn(&client->dev, "Oscillator not enabled. "
"Set time to enable.\n");
/* Register sysfs hooks */
err = device_create_file(&client->dev, &dev_attr_control);
if (err)
dev_err(&client->dev, "Unable to create sysfs entry: %s\n",
dev_attr_control.attr.name);
return 0;
}
static const struct i2c_device_id ds1672_id[] = {
{ "ds1672", 0 },
{ }
};
MODULE_DEVICE_TABLE(i2c, ds1672_id);
static const struct of_device_id ds1672_of_match[] = {
{ .compatible = "dallas,ds1672" },
{ }
};
MODULE_DEVICE_TABLE(of, ds1672_of_match);
static struct i2c_driver ds1672_driver = {
.driver = {
.name = "rtc-ds1672",
.of_match_table = of_match_ptr(ds1672_of_match),
},
.probe = &ds1672_probe,
.id_table = ds1672_id,
};
module_i2c_driver(ds1672_driver);
MODULE_AUTHOR("Alessandro Zummo <a.zummo@towertech.it>");
MODULE_DESCRIPTION("Dallas/Maxim DS1672 timekeeper driver");
MODULE_LICENSE("GPL");