linux spi write

#include <linux/module.h>
#include <linux/spi/spidev.h>
#include <linux/fs.h>
#include <linux/uaccess.h>

static struct spi_device *spi_dev;
static int major;

static ssize_t spi_write(struct file *file, const char __user *ubuf, size_t count, loff_t *ppos) {
    char buf[count];
    int ret;

    if (copy_from_user(buf, ubuf, count)) {
        return -EFAULT;
    }

    ret = spi_write_then_read(spi_dev, buf, count, NULL, 0);
    if (ret < 0) {
        return ret;
    }

    return count;
}

static struct file_operations spi_fops = {
    .write = spi_write,
};

static int __init spi_init(void) {
    struct spi_board_info spi_info = {
        .modalias = "spidev",
        .max_speed_hz = 500000,
        .bus_num = 0,
        .chip_select = 0,
    };

    spi_dev = spi_new_device(spi_busnum_to_master(0), &spi_info);
    if (!spi_dev) {
        return -ENODEV;
    }

    major = register_chrdev(0, "spi_device", &spi_fops);
    if (major < 0) {
        spi_unregister_device(spi_dev);
        return major;
    }

    return 0;
}

static void __exit spi_exit(void) {
    unregister_chrdev(major, "spi_device");
    spi_unregister_device(spi_dev);
}

module_init(spi_init);
module_exit(spi_exit);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("SPI Write Example");
MODULE_AUTHOR("Your Name");