Use of urb in Linux USB driver

Usb_alloc_urb
Usb_free_urb
Allocate and release

Urb filling:
Specify the urb type, which can be Ctrl, bulk, Int, or ISO.
Enter the callback function.

Usb_submit_urb
Usb_unlink_urb
Fill the urb structure or remove it from the USB system.

When the urb type is ISO or Int, an urb callback function may be called multiple times.

Bulk, you can submit the read or write urb, the callback function is used to notify the end of a USB transfer.

CTRL is the same as bulk.

/Drivers/USB. C contains the source code of most USB APIs.