diff options
| -rw-r--r-- | Documentation/ABI/stable/sysfs-driver-w1_ds2438 | 7 | ||||
| -rw-r--r-- | Documentation/w1/slaves/w1_ds2438.rst | 11 | ||||
| -rw-r--r-- | drivers/w1/slaves/w1_ds2438.c | 49 |
3 files changed, 66 insertions, 1 deletions
diff --git a/Documentation/ABI/stable/sysfs-driver-w1_ds2438 b/Documentation/ABI/stable/sysfs-driver-w1_ds2438 index fa47437c11d9..d2e7681cc287 100644 --- a/Documentation/ABI/stable/sysfs-driver-w1_ds2438 +++ b/Documentation/ABI/stable/sysfs-driver-w1_ds2438 @@ -4,3 +4,10 @@ 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 + +What: /sys/bus/w1/devices/.../offset +Date: April 2021 +Contact: Luiz Sampaio <sampaio.ime@gmail.com> +Description: write the contents to the offset register of the DS2438 + see Documentation/w1/slaves/w1_ds2438.rst for detailed information +Users: any user space application which wants to communicate with DS2438 diff --git a/Documentation/w1/slaves/w1_ds2438.rst b/Documentation/w1/slaves/w1_ds2438.rst index ac8d0d4b0d0e..5c5573991351 100644 --- a/Documentation/w1/slaves/w1_ds2438.rst +++ b/Documentation/w1/slaves/w1_ds2438.rst @@ -22,7 +22,7 @@ is also often used in weather stations and applications such as: rain gauge, wind speed/direction measuring, humidity sensing, etc. Current support is provided through the following sysfs files (all files -except "iad" are readonly): +except "iad" and "offset" are readonly): "iad" ----- @@ -52,6 +52,15 @@ 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. +"offset" +------- +This file controls the 2-byte Offset Register of the chip. +Writing a 2-byte value will change the Offset Register, which changes the +current measurement done by the chip. Changing this register to the two's complement +of the current register while forcing zero current through the load will calibrate +the chip, canceling offset errors in the current ADC. + + "temperature" ------------- Opening and reading this file initiates the CONVERT_T (temperature conversion) diff --git a/drivers/w1/slaves/w1_ds2438.c b/drivers/w1/slaves/w1_ds2438.c index 42080ae779f0..ca64f99c8f3d 100644 --- a/drivers/w1/slaves/w1_ds2438.c +++ b/drivers/w1/slaves/w1_ds2438.c @@ -193,6 +193,34 @@ static int w1_ds2438_change_config_bit(struct w1_slave *sl, u8 mask, u8 value) return -1; } +static int w1_ds2438_change_offset_register(struct w1_slave *sl, u8 *value) +{ + unsigned int retries = W1_DS2438_RETRIES; + u8 w1_buf[9]; + u8 w1_page1_buf[DS2438_PAGE_SIZE + 1 /*for CRC*/]; + + if (w1_ds2438_get_page(sl, 1, w1_page1_buf) == 0) { + memcpy(&w1_buf[2], w1_page1_buf, DS2438_PAGE_SIZE - 1); /* last register reserved */ + w1_buf[7] = value[0]; /* change only offset register */ + w1_buf[8] = value[1]; + while (retries--) { + if (w1_reset_select_slave(sl)) + continue; + w1_buf[0] = W1_DS2438_WRITE_SCRATCH; + w1_buf[1] = 0x01; /* write to page 1 */ + w1_write_block(sl->master, w1_buf, 9); + + if (w1_reset_select_slave(sl)) + continue; + w1_buf[0] = W1_DS2438_COPY_SCRATCH; + w1_buf[1] = 0x01; + w1_write_block(sl->master, w1_buf, 2); + return 0; + } + } + return -1; +} + static int w1_ds2438_get_voltage(struct w1_slave *sl, int adc_input, uint16_t *voltage) { @@ -364,6 +392,25 @@ static ssize_t page1_read(struct file *filp, struct kobject *kobj, return ret; } +static ssize_t offset_write(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; + + mutex_lock(&sl->master->bus_mutex); + + if (w1_ds2438_change_offset_register(sl, buf) == 0) + 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) @@ -430,6 +477,7 @@ 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_WO(offset, 2); 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 */); @@ -438,6 +486,7 @@ static struct bin_attribute *w1_ds2438_bin_attrs[] = { &bin_attr_iad, &bin_attr_page0, &bin_attr_page1, + &bin_attr_offset, &bin_attr_temperature, &bin_attr_vad, &bin_attr_vdd, |