linux gadet

Linux Gadget是一种在Linux内核中实现的USB设备模拟框架。它允许开发人员将Linux设备转换为USB设备，以便与主机进行通信。通过使用Gadget驱动程序，可以实现各种类型的USB设备，如存储设备、网络设备、音频设备等。

以下是一个使用Linux Gadget框架创建USB存储设备的示例：

#include <linux/usb/ch9.h>

// 定义USB设备描述符
static struct usb_device_descriptor device_desc = {
    .bLength = USB_DT_DEVICE_SIZE,
    .bDescriptorType = USB_DT_DEVICE,
    .bcdUSB = cpu_to_le16(0x0200),
    .bDeviceClass = USB_CLASS_PER_INTERFACE,
    .bDeviceSubClass = 0,
    .bDeviceProtocol = 0,
    .bMaxPacketSize0 = USB_MAX_PACKET_SIZE,
    .idVendor = cpu_to_le16(0x1234),
    .idProduct = cpu_to_le16(0x5678),
    .bcdDevice = cpu_to_le16(0x0100),
    .iManufacturer = 1,
    .iProduct = 2,
    .iSerialNumber = 3,
    .bNumConfigurations = 1,
};

// 定义USB配置描述符
static struct usb_config_descriptor config_desc = {
    .bLength = USB_DT_CONFIGURATION_SIZE,
    .bDescriptorType = USB_DT_CONFIGURATION,
    .wTotalLength = cpu_to_le16(sizeof(struct usb_config_descriptor)),
    .bNumInterfaces = 1,
    .bConfigurationValue = 1,
    .iConfiguration = 0,
    .bmAttributes = USB_CONFIG_ATT_ONE | USB_CONFIG_ATT_SELFPOWER,
    .bMaxPower = 0x32,
};

// 定义USB接口描述符
static struct usb_interface_descriptor interface_desc = {
    .bLength = USB_DT_INTERFACE_SIZE,
    .bDescriptorType = USB_DT_INTERFACE,
    .bInterfaceNumber = 0,
    .bAlternateSetting = 0,
    .bNumEndpoints = 2,
    .bInterfaceClass = USB_CLASS_MASS_STORAGE,
    .bInterfaceSubClass = USB_SUBCLASS_SCSI,
    .bInterfaceProtocol = USB_PROTOCOL_BULK,
    .iInterface = 0,
};

// 定义USB端点描述符
static struct usb_endpoint_descriptor endpoint_desc[] = {
    {
        .bLength = USB_DT_ENDPOINT_SIZE,
        .bDescriptorType = USB_DT_ENDPOINT,        .bEndpointAddress = USB_DIR_IN,
        .bmAttributes = USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize = cpu_to_le16(512),
        .bInterval = 0,
    },
    {
        .bLength = USB_DT_ENDPOINT_SIZE,
        .bDescriptorType = USB_DT_ENDPOINT,
        .bEndpointAddress = USB_DIR_OUT,
        .bmAttributes = USB_ENDPOINT_XFER_BULK,
        .wMaxPacketSize = cpu_to_le16(512),
        .bInterval = 0,
    },
};

// 定义USB字符串描述符
static struct usb_string strings[] = {
    [0] = {
        .s = "Manufacturer",
    },
    [1] = {
        .s = "Product",
    },
    [2] = {
        .s = "SerialNumber",
    },
};

// 定义USB设备描述符表
static struct usb_descriptor_header *descriptors[] = {
    (struct usb_descriptor_header *)&device_desc,
    (struct usb_descriptor_header *)&config_desc,
    (struct usb_descriptor_header *)&interface_desc,
    (struct usb_descriptor_header *)&endpoint_desc[0],    (struct usb_descriptor_header *)&endpoint_desc[1],
    (struct usb_descriptor_header *)&strings[0],
    (struct usb_descriptor_header *)&strings[1],
    (struct usb_descriptor_header *)&strings[2],
    NULL,
};

// 初始化USB设备
static int __init usb_gadget_init(void)
{
    struct usb_gadget *gadget;
    int ret;

    // 创建USB设备
    gadget = usb_get_gadget(usb_gadget_driver);
    if (!gadget) {
        pr_err("Failed to get gadget\n");
        return -ENODEV;
    }

    // 设置USB设备描述符表
    ret = usb_gadget_set_selfpowered(gadget);
    if (ret) {
        pr_err("Failed to set selfpowered: %d\n", ret);
        return ret;
    }

    // 注册USB设备
    ret = usb_gadget_register_driver(usb_gadget_driver);
    if (ret) {
        pr_err("Failed to register gadget driver: %d\n", ret);
        return ret;
    }

    return 0;
}

// 卸载USB设备
static void __exit usb_gadget_exit(void)
{
    usb_gadget_unregister_driver(usb_gadget_driver);
}

module_init(usb_gadget_init);
module_exit(usb_gadget_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Your Name");
MODULE_DESCRIPTION("Linux Gadget Example");

这是一个简单的示例，它创建了一个USB存储设备，并定义了设备描述符、配置描述符、接口描述符、端点描述符和字符串描述符。通过编译和加载该模块，您可以将Linux设备转换为USB存储设备。