10 concurrency and synchronization module

10-ConcurrencyAndSynchronization/Makefile

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+NAME = mpu6050
+
+ifneq ($(KERNELRELEASE),)
+
+obj-m := $(NAME).o
+
+else
+
+NAMELINUX ?= [email protected]
+MODULEDIR ?= /lib/modules/4.19.83-sunxi/kernel/drivers/iio/accel
+KERNELDIR ?= /home/dmitry/GL/orange-pi-4.19.83
+DTSDIR ?= $(PWD)/dtsi
+
+export ARCH = arm
+export CROSS_COMPILE ?= arm-linux-gnueabihf-
+
+.PHONY: all clean
+
+all: $(NAME).c
+	$(MAKE) -C $(KERNELDIR) M=$(CURDIR) modules
+
+dtbo:
+	$(KERNELDIR)/scripts/dtc/dtc -I dts -O dtb \
+		-o $(DTSDIR)/$(NAME).dtbo \
+		$(DTSDIR)/$(NAME).dtsi
+
+copymod: $(NAME).ko
+	scp $< $(NAMELINUX):$(MODULEDIR)
+
+copysshid:
+	ssh-copy-id -i ~/.ssh/id_rsa.pub $(NAMELINUX)
+
+copydtbo:
+	scp $(PWD)/dtsi/$(NAME).dtbo \
+		$(NAMELINUX):/boot/overlay-user
+
+clean:
+	$(MAKE) -C $(KERNELDIR) M=$(CURDIR) clean
+	-rm $(DTSDIR)/$(NAME).dtbo
+
+endif

10-ConcurrencyAndSynchronization/README.md

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+# Concurrency and synchronization
+
+## Homework
+
+**(based on MPU6050 driver)**
+
+_NB_:
+Communication with peripheral device on i2c is quite slow asynchronous process
+which responsiveness depends on the slave latency and bus utilisation.  
+Thus generally it's better to be done in background process.
+
+1. Move interaction with MPU6050 into separate thread.
+
+2. Protect static data of the driver (`g_mpu6050_data` in the master)
+for the case of concurrent access.
+
+3. Limit interaction with MPU6050 in case of frequent requests:  
+Define validity interval - if the latest read data is older than this threshold
+then new data reading is performed, otherwise previously read data is returned.  
+(This threshold should be configurable parameter with reasonable default.)
+

10-ConcurrencyAndSynchronization/dtsi/mpu6050.dtsi

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+/dts-v1/;
+/plugin/;
+
+/ {
+	compatible = "allwinner,sun8i-h3";
+
+	fragment@0 {
+		target = <&i2c0>;
+		__overlay__ {
+			status = "okay";
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			mpu: mpu6050@68 {
+				compatible = "gl, mpu6050";
+				reg = <0x68>;
+				delay_ms = <10000>;
+				status = "okay";
+			};
+		};
+	};
+};

10-ConcurrencyAndSynchronization/mpu6050-regs.h

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+#ifndef _MPU6050_REGS_H
+#define _MPU6050_REGS_H
+
+/* Registed addresses */
+#define REG_CONFIG			0x1A
+#define REG_GYRO_CONFIG		0x1B
+#define REG_ACCEL_CONFIG	0x1C
+#define REG_FIFO_EN			0x23
+#define REG_INT_PIN_CFG		0x37
+#define REG_INT_ENABLE		0x38
+#define REG_ACCEL_XOUT_H	0x3B
+#define REG_ACCEL_XOUT_L	0x3C
+#define REG_ACCEL_YOUT_H	0x3D
+#define REG_ACCEL_YOUT_L	0x3E
+#define REG_ACCEL_ZOUT_H	0x3F
+#define REG_ACCEL_ZOUT_L	0x40
+#define REG_TEMP_OUT_H		0x41
+#define REG_TEMP_OUT_L		0x42
+#define REG_GYRO_XOUT_H		0x43
+#define REG_GYRO_XOUT_L		0x44
+#define REG_GYRO_YOUT_H		0x45
+#define REG_GYRO_YOUT_L		0x46
+#define REG_GYRO_ZOUT_H		0x47
+#define REG_GYRO_ZOUT_L		0x48
+#define REG_USER_CTRL		0x6A
+#define REG_PWR_MGMT_1		0x6B
+#define REG_PWR_MGMT_2		0x6C
+#define REG_WHO_AM_I		0x75
+
+/* Register values */
+#define MPU6050_WHO_AM_I	0x68
+
+#endif /* _MPU6050_REGS_H */