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w1: ds2438: adding support for reading page1

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Added a sysfs entry to support reading the page1 registers. This registers
contain Elapsed Time Meter (ETM) data, which shows for how long the chip is
on, as well as an Offset Register data, which can be used to calibrate the
current measurement of the chip.

Signed-off-by: Luiz Sampaio <sampaio.ime@gmail.com>
Link: https://lore.kernel.org/r/20210519223046.13798-6-sampaio.ime@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Luiz Sampaio 2021-05-19 19:30:45 -03:00 • committed by Greg Kroah-Hartman
parent 1f5e7518f0
commit fd6ec5d795
3 changed files with 55 additions and 0 deletions
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6
Documentation/ABI/stable/sysfs-driver-w1_ds2438 Normal file
View file

@ -0,0 +1,6 @@
What: /sys/bus/w1/devices/.../page1
Date: April 2021
Contact: Luiz Sampaio <sampaio.ime@gmail.com>
Description: read the contents of the page1 of the DS2438
see Documentation/w1/slaves/w1_ds2438.rst for detailed information
Users: any user space application which wants to communicate with DS2438

8
Documentation/w1/slaves/w1_ds2438.rst
View file

@ -44,6 +44,14 @@ Internally when this file is read, the additional CRC byte is also obtained
from the slave device. If it is correct, the 8 bytes page data are passed
to userspace, otherwise an I/O error is returned.
"page1"
-------
This file provides full 8 bytes of the chip Page 1 (01h).
This page contains the ICA, elapsed time meter and current offset data of the DS2438.
Internally when this file is read, the additional CRC byte is also obtained
from the slave device. If it is correct, the 8 bytes page data are passed
to userspace, otherwise an I/O error is returned.
"temperature"
-------------
Opening and reading this file initiates the CONVERT_T (temperature conversion)

41
drivers/w1/slaves/w1_ds2438.c
View file

@ -49,6 +49,15 @@
#define DS2438_CURRENT_MSB 0x06
#define DS2438_THRESHOLD 0x07
/* Page #1 definitions */
#define DS2438_ETM_0 0x00
#define DS2438_ETM_1 0x01
#define DS2438_ETM_2 0x02
#define DS2438_ETM_3 0x03
#define DS2438_ICA 0x04
#define DS2438_OFFSET_LSB 0x05
#define DS2438_OFFSET_MSB 0x06
static int w1_ds2438_get_page(struct w1_slave *sl, int pageno, u8 *buf)
{
unsigned int retries = W1_DS2438_RETRIES;
@ -325,6 +334,36 @@ static ssize_t page0_read(struct file *filp, struct kobject *kobj,
return ret;
}
static ssize_t page1_read(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr, char *buf,
loff_t off, size_t count)
{
struct w1_slave *sl = kobj_to_w1_slave(kobj);
int ret;
u8 w1_buf[DS2438_PAGE_SIZE + 1 /*for CRC*/];
if (off != 0)
return 0;
if (!buf)
return -EINVAL;
mutex_lock(&sl->master->bus_mutex);
/* Read no more than page1 size */
if (count > DS2438_PAGE_SIZE)
count = DS2438_PAGE_SIZE;
if (w1_ds2438_get_page(sl, 1, w1_buf) == 0) {
memcpy(buf, &w1_buf, count);
ret = count;
} else
ret = -EIO;
mutex_unlock(&sl->master->bus_mutex);
return ret;
}
static ssize_t temperature_read(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr, char *buf,
loff_t off, size_t count)
@ -390,6 +429,7 @@ static ssize_t vdd_read(struct file *filp, struct kobject *kobj,
static BIN_ATTR_RW(iad, 0);
static BIN_ATTR_RO(page0, DS2438_PAGE_SIZE);
static BIN_ATTR_RO(page1, DS2438_PAGE_SIZE);
static BIN_ATTR_RO(temperature, 0/* real length varies */);
static BIN_ATTR_RO(vad, 0/* real length varies */);
static BIN_ATTR_RO(vdd, 0/* real length varies */);
@ -397,6 +437,7 @@ static BIN_ATTR_RO(vdd, 0/* real length varies */);
static struct bin_attribute *w1_ds2438_bin_attrs[] = {
&bin_attr_iad,
&bin_attr_page0,
&bin_attr_page1,
&bin_attr_temperature,
&bin_attr_vad,
&bin_attr_vdd,