A usb_fifo_methods structure defines a USB driver’s entry points. You can think of struct usb_fifo_methods as struct cdevsw, but for USB drivers.

struct usb_fifo_methods is defined in the <dev/usb/usbdi.h> header as follows:

struct usb_fifo_methods {
        /* Executed Unlocked */
        usb_fifo_open_t         *f_open;
        usb_fifo_close_t        *f_close;
        usb_fifo_ioctl_t        *f_ioctl;
        usb_fifo_ioctl_t        *f_ioctl_post;

        /* Executed With Mutex Locked */
        usb_fifo_cmd_t          *f_start_read;
        usb_fifo_cmd_t          *f_stop_read;
        usb_fifo_cmd_t          *f_start_write;
        usb_fifo_cmd_t          *f_stop_write;
        usb_fifo_filter_t       *f_filter_read;
        usb_fifo_filter_t       *f_filter_write;

        const char              *basename[4];
        const char              *postfix[4];
};

The FreeBSD kernel provides the following functions for working with usb_fifo_methods ...