用户态SPI接口与传感器编程实践-RZMPU工业控制教程连载（12）

spidev_fdx [-h] [-m N] [-r N] /dev/spidevB.D* -h: 打印用法* -m N：先写 1 个字节 0xaa，再读 N 个字节，**注意：**不是同时写同时读* -r N：读 N 个字节

 spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) { //用于处理 SPI 设备的 ioctl 命令。它接收用户空间传递的参数，并执行 SPI 传输。 int val; int err; unsigned char tx_buf[2]; unsigned char rx_buf[2]; struct spi_message msg; struct spi_transfer xfer[1]; int status; memset(&xfer[0], 0, sizeof(xfer));//用户空间拷贝数据到内核空间 /* copy_from_user */ err = copy_from_user(&val, (const void __user *)arg, sizeof(int)); printk("spidev_ioctl get val from user: %d\n", val); /* 发起 SPI 传输: */ /* 1. 把 val 修改为正确的格式 */ val <<= 2; /* bit0,bit1 = 0b00 */ val &= 0xFFC; /* 只保留 10bit */ tx_buf[1] = val & 0xff; tx_buf[0] = (val>>8) & 0xff; /* 2. 发起 SPI 传输同时写\读 */ /* 2.1 构造 transfer * 2.2 加入 message * 2.3 调用 spi_sync */ xfer[0].tx_buf = tx_buf; xfer[0].rx_buf = rx_buf; xfer[0].len = 2;spi_message_init(&msg);spi_message_add_tail(&xfer[0], &msg);status = spi_sync(dac, &msg); /* 3. 修改读到的数据的格式 */val = (rx_buf[0] << 8) | (rx_buf[1]);val >>= 2; /* copy_to_user */ err = copy_to_user((void __user *)arg, &val, sizeof(int));return 0;} //定义了字符设备的操作函数 static const struct file_operations spidev_fops = { .owner = THIS_MODULE,/* REVISIT switch to aio primitives, so that userspace * gets more complete API coverage. It'll simplify things * too, except for the locking. */.unlocked_ioctl = spidev_ioctl, };static struct class *spidev_class; static const struct of_device_id spidev_dt_ids[] = {{ .compatible = "100ask,dac" }, {},}; /*-------------------------------------------------------------------------*/ static int spidev_probe(struct spi_device *spi){/* 1. 记录 spi_device */ dac = spi; /* 2. 注册字符设备 */major = register_chrdev(0, "100ask_dac", &spidev_fops);spidev_class = class_create(THIS_MODULE, "100ask_dac"); device_create(spidev_class, NULL, MKDEV(major, 0), NULL, "100ask_dac");return 0; } static int spidev_remove(struct spi_device *spi){ /* 反注册字符设备 */ device_destroy(spidev_class, MKDEV(major, 0));class_destroy(spidev_class);unregister_chrdev(major, "100ask_dac");return 0;}//定义了 SPI 驱动的相关信息，包括设备名、探测函数、移除函数等。static struct spi_driver spidev_spi_driver = {.driver = {name = "100ask_spi_dac_drv",of_match_table = of_match_ptr(spidev_dt_ids), },probe = spidev_probe,remove = spidev_remove, /* NOTE: suspend/resume methods are not necessary here. * We don't do anything except pass the requests to/from * the underlying controller. The refrigerator handles* most issues; the controller driver handles the rest.*/ }; /*-------------------------------------------------------------------------*///在模块初始化时被调用，用于注册 SPI 驱动 static int __init spidev_init(void){ int status;printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__); status = spi_register_driver(&spidev_spi_driver); if (status < 0) { }return status; }module_init(spidev_init); //退出时被调用，用于反注册 SPI 驱动static void __exit spidev_exit(void){ printk("%s %s %d\n", __FILE__, __FUNCTION__, __LINE__); spi_unregister_driver(&spidev_spi_driver); }

int main(int argc, char **argv){ int fd; //文件描述符unsigned int val;int status;
unsigned char tx_buf[2];unsigned char rx_buf[2];
 if (argc != 3){printf("Usage: %s /dev/100ask_dac \n", argv[0]);return 0;}
fd = open(argv[1], O_RDWR); //打开指定的设备文件if (fd < 0) {printf("can not open %s\n", argv[1]);return 1;}//将命令行参数转换为整数，并将其左移两位，保留最低的 10 位。val = strtoul(argv[2], NULL, 0);
status = ioctl(fd, SPI_IOC_WR, &val);// 发起 SPI 传输，将数据写入设备if (status < 0) {printf("SPI_IOC_WR\n");return -1;}
 /* 打印 */printf("Pre val = %d\n", val);

return 0;}

KERN_DIR = /home/ubuntu/remi-pi/myir-renesas-linux
all:make -C $(KERN_DIR) M=`pwd` modules$(CC) -o dac_test dac_test.c
clean:make -C $(KERN_DIR) M=`pwd` modules cleanrm -rf modules.order dac_test
obj-m += dac_drv.o

ubuntu@ubuntu2004:~/remi-pi/myir-renesas-linux$ source /opt/remi-sdk/environment-setup-aarch64-poky-linuxubuntu@ubuntu2004:~/remi-pi/myir-renesas-linux$ make ARCH=arm64 Image dtbs -j4ubuntu@ubuntu2004:~/remi-pi/myir-renesas-linux$ make modules_prepare

source /opt/remi-sdk/environment-setup-aarch64-poky-linuxmake

scp ./input_read_fasync root@192.168.5.9:/mnt/

ubuntu@ubuntu2004:~/remi-pi/myir-renesas-linux$ cd arch/arm64/boot/dts/myir/ubuntu@ubuntu2004:~/remi-pi/myir-renesas-linux$ vi mys-rzg2l-smarc-base.dtsi

&spi0 { pinctrl-0 = <&spi0_pins>; pinctrl-names = "default"; status = "okay"; spidev@0{ #address-cellss=<1>;#size-cells=<1>;compatible = "rohm,dh2228fv";spi-max-frequency = <80000000>; reg = <0>;status = "disabled"; }; mydac { compatible = "100ask,dac"; reg = <0>; spi-max-frequency = <1000000>; status = "okay"; };};

ubuntu@ubuntu2004:~/remi-pi/myir-renesas-linux$ make ARCH=arm64 dtbs -j8

root@myir-remi-1g:~# mount /dev/mmcblk0p1 /mnt/root@myir-remi-1g:~# ifconfig eth0 192.168.5.9

ubuntu@ubuntu2004:~/remi-pi/myir-renesas-linux$ cp arch/arm64/boot/dts/myir/mys-rzg2l-*.dtb ../build/ubuntu@ubuntu2004:~/remi-pi$ scp ./build/*.dtb root@192.168.5.9:/mnt

root@myir-remi-1g:~# syncroot@myir-remi-1g:~# reboot

ubuntu@ubuntu2004:~/C-Test/dac_use_mydrv$ scp ./dac_test root@192.168.5.9:/mnt/ubuntu@ubuntu2004:~/C-Test/dac_use_mydrv$ scp ./dac_drv.ko root@192.168.5.9:/mnt/

root@myir-remi-1g:~# cd /mnt/root@myir-remi-1g:/mnt# lsdac_drv.ko dac_test

root@myir-remi-1g:/mnt# insmod dac_drv.koroot@myir-remi-1g:/mnt# ./dac_test /dev/100ask_dac 1000root@myir-remi-1g:/mnt# ./dac_test /dev/100ask_dac 500root@myir-remi-1g:/mnt# ./dac_test /dev/100ask_dac 0