This driver handles DHT11 and DHT22 sensors.
Signed-off-by: Harald Geyer <harald@xxxxxxxxx>
---
Now this is tested with both DHT11 and DHT22 hardware, so I'm asking
for full review this time. As this hadn't had a thorough review yet,
I don't list changes to the last version posted.
Thanks,
Harald
.../bindings/iio/humidity/dht11-gpio.txt | 14 +
drivers/iio/Kconfig | 1 +
drivers/iio/Makefile | 1 +
drivers/iio/humidity/Kconfig | 14 +
drivers/iio/humidity/Makefile | 5 +
drivers/iio/humidity/dht11-gpio.c | 332 ++++++++++++++++++++
6 files changed, 367 insertions(+), 0 deletions(-)
create mode 100644 Documentation/devicetree/bindings/iio/humidity/dht11-gpio.txt
create mode 100644 drivers/iio/humidity/Kconfig
create mode 100644 drivers/iio/humidity/Makefile
create mode 100644 drivers/iio/humidity/dht11-gpio.c
diff --git a/Documentation/devicetree/bindings/iio/humidity/dht11-gpio.txt b/Documentation/devicetree/bindings/iio/humidity/dht11-gpio.txt
new file mode 100644
index 0000000..c91bb27
--- /dev/null
+++ b/Documentation/devicetree/bindings/iio/humidity/dht11-gpio.txt
@@ -0,0 +1,14 @@
+* DHT11 humidity/temperature sensor (and compatibles like DHT22)
+
+Required properties:
+ - compatible: Should be "dht11-gpio"
+ - gpios: Should specify the GPIO connected to the sensors data
+ line, see "gpios property" in
+ Documentation/devicetree/bindings/gpio/gpio.txt.
+
+Example:
+
+humidity_sensor {
+ compatible = "dht11-gpio";
+ gpios = <&gpio0 6 0>;
+}
diff --git a/drivers/iio/Kconfig b/drivers/iio/Kconfig
index 90cf0cd..a5ed882 100644
--- a/drivers/iio/Kconfig
+++ b/drivers/iio/Kconfig
@@ -65,6 +65,7 @@ source "drivers/iio/common/Kconfig"
source "drivers/iio/dac/Kconfig"
source "drivers/iio/frequency/Kconfig"
source "drivers/iio/gyro/Kconfig"
+source "drivers/iio/humidity/Kconfig"
source "drivers/iio/imu/Kconfig"
source "drivers/iio/light/Kconfig"
source "drivers/iio/magnetometer/Kconfig"
diff --git a/drivers/iio/Makefile b/drivers/iio/Makefile
index bcf7e9e..b3b5096 100644
--- a/drivers/iio/Makefile
+++ b/drivers/iio/Makefile
@@ -18,6 +18,7 @@ obj-y += common/
obj-y += dac/
obj-y += gyro/
obj-y += frequency/
+obj-y += humidity/
obj-y += imu/
obj-y += light/
obj-y += magnetometer/
diff --git a/drivers/iio/humidity/Kconfig b/drivers/iio/humidity/Kconfig
new file mode 100644
index 0000000..aa7e481
--- /dev/null
+++ b/drivers/iio/humidity/Kconfig
@@ -0,0 +1,14 @@
+#
+# humidity sensor drivers
+#
+menu "Humidity sensors"
+
+config DHT11_GPIO
+ tristate "DHT11 (and compatible sensors) driver"
+ help
+ This driver supports reading data via a single interrupts
+ generating GPIO line. Currently tested are DHT11 and DHT22.
+ Other sensors should work as well as long as they speak the
+ same protocol.
+
+endmenu
diff --git a/drivers/iio/humidity/Makefile b/drivers/iio/humidity/Makefile
new file mode 100644
index 0000000..5e8226f
--- /dev/null
+++ b/drivers/iio/humidity/Makefile
@@ -0,0 +1,5 @@
+#
+# Makefile for IIO humidity sensor drivers
+#
+
+obj-$(CONFIG_DHT11_GPIO) += dht11-gpio.o
diff --git a/drivers/iio/humidity/dht11-gpio.c b/drivers/iio/humidity/dht11-gpio.c
new file mode 100644
index 0000000..fcbfa3e
--- /dev/null
+++ b/drivers/iio/humidity/dht11-gpio.c
@@ -0,0 +1,332 @@
+/*
+ * DHT11/DHT22 bit banging GPIO driver
+ *
+ * Copyright (c) Harald Geyer <harald@xxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/sysfs.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/wait.h>
+#include <linux/bitops.h>
+#include <linux/completion.h>
+#include <linux/delay.h>
+#include <linux/gpio.h>
+#include <linux/of_gpio.h>
+
+#include <linux/iio/iio.h>
+
+#define DRIVER_NAME "dht11-gpio"
+
+#define DATA_VALID_TIME 2000000000 /* 2s in ns */
+
+#define EDGES_PREAMBLE 4
+#define BITS_PER_READ 40
+#define EDGES_PER_READ (2*BITS_PER_READ + EDGES_PREAMBLE + 1)
+
+/* Data transmission timing (nano seconds) */
+#define STARTUP 18 /* ms */
+#define SENSOR_RESPONSE 80000
+#define START_BIT 50000
+#define DATA_BIT_LOW 27000
+#define DATA_BIT_HIGH 70000
+
+/* TODO?: Support systems without DT? */
+
+struct dht11_gpio {
+ struct device *dev;
+
+ int gpio;
+ int irq;
+
+ struct completion completion;
+
+ s64 timestamp;
+ int temperature;
+ int humidity;
+
+ /* num_edges: -1 means "no transmission in progress" */
+ int num_edges;
+ struct {s64 ts; int value; } edges[EDGES_PER_READ];
+};
+
+/*
+ * dht11_edges_print: show the data as actually received by the
+ * driver.
+ * This is dead code, keeping it for now just in case somebody needs
+ * it for porting the driver to new sensor HW, etc.
+ *
+static void dht11_edges_print(struct dht11_gpio *dht11)
+{
+ int i;
+
+ for (i = 1; i < dht11->num_edges; ++i) {
+ pr_err("dht11: %d: %lld ns %s\n", i,
+ dht11->edges[i].ts - dht11->edges[i-1].ts,
+ dht11->edges[i-1].value ? "high" : "low");
+ }
+}
+*/
+
+static unsigned char dht11_gpio_decode_byte(int *timing, int threshold)
+{
+ unsigned char ret = 0;
+ int i;
+
+ for (i = 0; i < 8; ++i) {
+ ret <<= 1;
+ if (timing[i] >= threshold)
+ ++ret;
+ }
+
+ return ret;
+}
+
+static int dht11_gpio_decode(struct dht11_gpio *dht11, int offset)
+{
+ int i, t, timing[BITS_PER_READ], threshold, timeres = SENSOR_RESPONSE;
+ unsigned char temp_int, temp_dec, hum_int, hum_dec, checksum;
+
+ /* Calculate timestamp resolution */
+ for (i = 0; i < dht11->num_edges; ++i) {
+ t = dht11->edges[i].ts - dht11->edges[i-1].ts;
+ if (t > 0 && t < timeres)
+ timeres = t;
+ }
+ if (2*timeres > DATA_BIT_HIGH) {
+ pr_err("dht11-gpio: timeresolution %d too bad for decoding\n",
+ timeres);
+ return -EIO;
+ }
+ threshold = DATA_BIT_HIGH/timeres;
+ if (DATA_BIT_LOW/timeres + 1 >= threshold)
+ pr_err("dht11-gpio: WARNING: decoding ambiguous\n");
+
+ /* scale down with timeres and check validity */
+ for (i = 0; i < BITS_PER_READ; ++i) {
+ t = dht11->edges[offset + 2*i + 2].ts -
+ dht11->edges[offset + 2*i + 1].ts;
+ if (!dht11->edges[offset + 2*i + 1].value)
+ return -EIO; /* lost synchronisation */
+ timing[i] = t / timeres;
+ }
+
+ hum_int = dht11_gpio_decode_byte(timing, threshold);
+ hum_dec = dht11_gpio_decode_byte(&timing[8], threshold);
+ temp_int = dht11_gpio_decode_byte(&timing[16], threshold);
+ temp_dec = dht11_gpio_decode_byte(&timing[24], threshold);
+ checksum = dht11_gpio_decode_byte(&timing[32], threshold);
+
+ if (((hum_int + hum_dec + temp_int + temp_dec) & 0x00ff) != checksum)
+ return -EIO;
+
+ dht11->timestamp = iio_get_time_ns();
+ if (hum_int < 20) { /* DHT22 */
+ dht11->temperature = (((temp_int & 0x7f) << 8) + temp_dec) *
+ ((temp_int & 0x80) ? -100 : 100);
+ dht11->humidity = ((hum_int << 8) + hum_dec) * 100;
+ } else if (temp_dec == 0 && hum_dec == 0) { /* DHT11 */
+ dht11->temperature = temp_int * 1000;
+ dht11->humidity = hum_int * 1000;
+ } else {
+ dev_err(dht11->dev,
+ "Don't know how to decode data: %d %d %d %d\n",
+ hum_int, hum_dec, temp_int, temp_dec);
+ return -EIO;
+ }
+
+ return 0;
+}
+
+static int dht11_gpio_read_raw(struct iio_dev *iio_dev,
+ const struct iio_chan_spec *chan,
+ int *val, int *val2, long m)
+{
+ struct dht11_gpio *dht11 = iio_priv(iio_dev);
+ int ret = 0;
+
+ if (dht11->timestamp + DATA_VALID_TIME < iio_get_time_ns()) {
+ INIT_COMPLETION(dht11->completion);
+
+ dht11->num_edges = 0;
+ ret = gpio_direction_output(dht11->gpio, 0);
+ if (ret)
+ goto err;
+ msleep(STARTUP);
+ ret = gpio_direction_input(dht11->gpio);
+ if (ret)
+ goto err;
+
+ ret = wait_for_completion_killable_timeout(&dht11->completion,
+ HZ);
+ if (ret == 0 && dht11->num_edges < EDGES_PER_READ - 1) {
+ dev_err(&iio_dev->dev,
+ "Only %d signal edges detected\n",
+ dht11->num_edges);
+ ret = -ETIMEDOUT;
+ }
+ if (ret < 0)
+ goto err;
+
+ ret = dht11_gpio_decode(dht11,
+ dht11->num_edges == EDGES_PER_READ ?
+ EDGES_PREAMBLE : EDGES_PREAMBLE - 2);
+ if (ret)
+ goto err;
+ }
+
+ ret = IIO_VAL_INT;
+ if (chan->channel == 0)
+ *val = dht11->temperature;
+ else if (chan->channel == 1)
+ *val = dht11->humidity;
+ else
+ ret = -EINVAL;
+err:
+ dht11->num_edges = -1;
+ return ret;
+}
+
+static const struct iio_info dht11_gpio_iio_info = {
+ .driver_module = THIS_MODULE,
+ .read_raw = dht11_gpio_read_raw,
+};
+
+/*
+ * IRQ handler called on GPIO edges
+*/
+static irqreturn_t dht11_gpio_handle_irq(int irq, void *data)
+{
+ struct iio_dev *iio = data;
+ struct dht11_gpio *dht11 = iio_priv(iio);
+
+ /* TODO: Consider making the handler safe for IRQ sharing */
+ if (dht11->num_edges < EDGES_PER_READ && dht11->num_edges >= 0) {
+ dht11->edges[dht11->num_edges].ts = iio_get_time_ns();
+ dht11->edges[dht11->num_edges++].value =
+ gpio_get_value(dht11->gpio);
+
+ if (dht11->num_edges >= EDGES_PER_READ)
+ complete(&dht11->completion);
+ }
+
+ return IRQ_HANDLED;
+}
+
+static const struct iio_chan_spec dht11_gpio_chan_spec[] = {
+ { .type = IIO_TEMP, .channel = 0,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), },
+ { .type = IIO_HUMIDITYRELATIVE, .channel = 1,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+}
+};
+
+static const struct of_device_id dht11_gpio_dt_ids[] = {
+ { .compatible = "dht11-gpio", },
+ { }
+};
+MODULE_DEVICE_TABLE(of, dht11_gpio_dt_ids);
+
+static int dht11_gpio_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct device_node *node = dev->of_node;
+ struct dht11_gpio *dht11;
+ struct iio_dev *iio;
+ int ret = 0;
+
+ /* Allocate the IIO device. */
+ iio = devm_iio_device_alloc(dev, sizeof(*dht11));
+ if (!iio) {
+ dev_err(dev, "Failed to allocate IIO device\n");
+ return -ENOMEM;
+ }
+
+ dht11 = iio_priv(iio);
+ dht11->dev = dev;
+
+ dht11->gpio = ret = of_get_gpio(node, 0);
+ if (ret < 0)
+ return ret;
+ ret = devm_gpio_request_one(dev, dht11->gpio, GPIOF_IN, pdev->name);
+ if (ret)
+ return ret;
+
+ dht11->irq = gpio_to_irq(dht11->gpio);
+ if (dht11->irq < 0) {
+ dev_err(dev, "GPIO %d has no interrupt\n", dht11->gpio);
+ return -EINVAL;
+ }
+ ret = devm_request_irq(dev, dht11->irq, dht11_gpio_handle_irq,
+ IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
+ pdev->name, iio);
+ if (ret)
+ return ret;
+
+ dht11->timestamp = iio_get_time_ns() - DATA_VALID_TIME - 1;
+ dht11->num_edges = -1;
+
+ platform_set_drvdata(pdev, iio);
+
+ init_completion(&dht11->completion);
+ iio->name = pdev->name;
+ iio->dev.parent = &pdev->dev;
+ iio->info = &dht11_gpio_iio_info;
+ iio->modes = INDIO_DIRECT_MODE;
+ iio->channels = dht11_gpio_chan_spec;
+ iio->num_channels = ARRAY_SIZE(dht11_gpio_chan_spec);
+
+ /* Register IIO device. */
+ ret = iio_device_register(iio);
+ if (ret) {
+ dev_err(dev, "Failed to register IIO device\n");
+ return ret;
+ }
+
+ return 0;
+}
+
+static int dht11_gpio_remove(struct platform_device *pdev)
+{
+ struct iio_dev *iio = platform_get_drvdata(pdev);
+
+ iio_device_unregister(iio);
+
+ return 0;
+}
+
+static struct platform_driver dht11_gpio_driver = {
+ .driver = {
+ .name = DRIVER_NAME,
+ .owner = THIS_MODULE,
+ .of_match_table = dht11_gpio_dt_ids,
+ },
+ .probe = dht11_gpio_probe,
+ .remove = dht11_gpio_remove,
+};
+
+module_platform_driver(dht11_gpio_driver);
+
+MODULE_AUTHOR("Harald Geyer <harald@xxxxxxxxx>");
+MODULE_DESCRIPTION("DHT11 humidity/temperature sensor driver");
+MODULE_LICENSE("GPL v2");
+
--
1.7.2.5
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