Added BME680 Sensor Driver

.gitmodules

@@ -44,3 +44,6 @@
 [submodule "apps/LocationTriangulation"]
 	path = apps/LocationTriangulation
 	url = https://github.com/mangOH/LocationTriangulation
+[submodule "linux_kernel_modules/bme680/BME680_driver"]
+	path = linux_kernel_modules/bme680/BME680_driver
+	url = https://github.com/BoschSensortec/BME680_driver.git

linux_kernel_modules/bme680/3-bme680-i2c.mdef

+cflags:
+{
+    // This driver depends on IIO
+    -DCONFIG_IIO
+    -DDEBUG
+    -DSIERRA
+    -I$MANGOH_ROOT/linux_kernel_modules/bme680/BME680_driver
+}
+
+sources:
+{
+    ./BME680_driver/bme680.c
+    bme680-i2c.c
+    bme680-regmap.c
+}
+

linux_kernel_modules/bme680/bme680-regmap.c

+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+
+#include "bme680_defs.h"
+
+static bool bme680_is_writeable_reg(struct device *dev, unsigned int reg)
+{
+	switch (reg) {
+	case BME680_CONF_HEAT_CTRL_ADDR:
+	case BME680_CONF_ODR_RUN_GAS_NBC_ADDR:
+	case BME680_CONF_OS_H_ADDR:
+	case BME680_CONF_T_P_MODE_ADDR:
+        case BME680_SOFT_RESET_ADDR:
+		return true;
+	default:
+                if (((reg >= BME680_CONF_ODR_FILT_ADDR) && 
+                     (reg <= BME680_CONF_ODR_FILT_ADDR + BME680_FILTER_SIZE_127)) ||
+                    ((reg >= BME680_ADDR_SENS_CONF_START) && 
+                     (reg <= BME680_ADDR_SENS_CONF_START + BME680_FILTER_SIZE_7)))
+                        return true;
+
+                dev_err(dev, "%s(): Error register(0x%04x) not writable\n", __func__, reg);
+		return false;
+	};
+}
+
+static bool bme680_is_volatile_reg(struct device *dev, unsigned int reg)
+{
+	if (((reg >= BME680_ADDR_GAS_CONF_START) && (reg <= BME680_ADDR_GAS_CONF_START + 9)) ||
+            ((reg >= BME680_ADDR_SENS_CONF_START) && (reg <= BME680_ADDR_SENS_CONF_START + 9)))
+		return true;
+	
+	return false;
+}
+
+const struct regmap_config bme680_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+
+	.max_register = BME680_COEFF_ADDR2 + BME680_COEFF_ADDR2_LEN,
+	.cache_type = REGCACHE_RBTREE,
+
+	.writeable_reg = bme680_is_writeable_reg,
+	.volatile_reg = bme680_is_volatile_reg,
+};
+EXPORT_SYMBOL(bme680_regmap_config);

linux_kernel_modules/bme680/bme680_patch.txt

+--- ./BME680_driver/bme680.c	2018-05-15 10:35:44.730819635 -0700
++++ ./bme680.c	2018-05-15 09:55:23.278858200 -0700
+@@ -991,7 +991,12 @@
+ 		((int64_t) lookupTable1[gas_range])) >> 16;
+ 	var2 = (((int64_t) ((int64_t) gas_res_adc << 15) - (int64_t) (16777216)) + var1);
+ 	var3 = (((int64_t) lookupTable2[gas_range] * (int64_t) var1) >> 9);
++#ifdef SIERRA
++        var3 += (int64_t) var2 >> 1;
++        calc_gas_res = (uint32_t) do_div(var3, (int64_t) var2);
++#else
+ 	calc_gas_res = (uint32_t) ((var3 + ((int64_t) var2 >> 1)) / (int64_t) var2);
++#endif
+ 
+ 	return calc_gas_res;
+ }

linux_kernel_modules/iio/industrialio-core.c

@@ -70,6 +70,7 @@ static const char * const iio_chan_type_name_spec[] = {
 	[IIO_CCT] = "cct",
 	[IIO_PRESSURE] = "pressure",
 	[IIO_HUMIDITYRELATIVE] = "humidityrelative",
+        [IIO_GASRESISTANCE] = "gasresistance",
 };
 
 static const char * const iio_modifier_names[] = {