linux usb从设备加密问题

Question

我想实现一个嵌入式的linux设备，带sd卡，默认情况下在usb连接电脑后不能打开嵌入式设备上的sd卡文件，在设备端设置过后才可以打开，或者在电脑上位机端输入密码后才能打开。请问这个在嵌入式linux设备端怎么去实现？谢谢

Answer 1

以下回答参考 皆我百晓生、券券喵儿 等免费微信小程序相关内容作答，并由本人整理回复。

Linux内核支持USB驱动，你可以使用usb-hid设备来控制SD卡的访问权限。

以下是一个简单的示例，展示了如何使用usb-hid设备和usb-storage设备来控制SD卡的读写：

#include <stdio.h>
#include <stdlib.h>

#define USB_HID_VENDOR_ID 0x1809 // SD Card vendor ID
#define USB_HID_PRODUCT_ID 0x5004 // SD Card product ID

int main() {
    struct hid_device *dev;
    int ret;

    /* Create a new HID device */
    dev = hid_new(NULL);
    if (dev == NULL) {
        printf("Failed to create HID device\n");
        return -1;
    }

    /* Add the HID device to the system */
    ret = hid_register(dev, &hid_hid_dev);
    if (ret != 0) {
        hid_free(dev);
        printf("Failed to register HID device: %s\n", hid_error(ret));
        return -1;
    }

    /* Open the HID device */
    hid_device_open(dev);

    /* Set up the USB driver for the HID device */
    ret = hid_driver_setup(&hid_driver, USB_HID_VENDOR_ID, USB_HID_PRODUCT_ID);
    if (ret != 0) {
        hid_device_close(dev);
        hid_free(dev);
        printf("Failed to setup USB driver: %s\n", hid_error(ret));
        return -1;
    }

    /* Start the USB driver */
    ret = hid_driver_start();
    if (ret != 0) {
        hid_device_close(dev);
        hid_free(dev);
        printf("Failed to start USB driver: %s\n", hid_error(ret));
        return -1;
    }

    /* Wait for the USB driver to be ready */
    while (!hid_driver_ready()) {}

    /* Enable USB storage support on the HID device */
    hid_storage_enable(dev, 0); // Enable block access mode

    /* Read from the SD card */
    uint8_t buffer[2] = {0};
    ret = hid_read(dev, buffer, sizeof(buffer), 10000);
    if (ret != 0) {
        printf("Failed to read from SD card: %s\n", hid_error(ret));
        hid_storage_disable(dev);
        hid_device_close(dev);
        hid_free(dev);
        return -1;
    }
    printf("Read from SD card: %d\n", buffer[0]);

    /* Write to the SD card */
    ret = hid_write(dev, buffer, sizeof(buffer), 10000);
    if (ret != 0) {
        printf("Failed to write to SD card: %s\n", hid_error(ret));
        hid_storage_disable(dev);
        hid_device_close(dev);
        hid_free(dev);
        return -1;
    }
    printf("Written to SD card: %d\n", buffer[0]);

    /* Disable USB storage support on the HID device */
    hid_storage_disable(dev);

    /* Free the HID device */
    hid_free(dev);

    return 0;
}

这段代码首先创建了一个新的HID设备，并添加到系统中。然后，它设置了USB驱动器以用于HID设备，开始USB驱动程序，等待其准备好。接着，它打开了HID设备并启动了USB驱动程序。最后，它开始读取和写入SD卡。

请注意，这只是一个基本的示例，实际应用可能需要更复杂的错误处理、安全检查和其他功能。此外，你还需要确保你的硬件能够正确地识别和响应这些命令。