useful documents, at the USB home page (see Resources). An excellent
introduction to the Linux USB subsystem can be found at the USB Working
Devices List (see Resources). It explains how the Linux USB subsystem is
useful documents, at the USB home page (see Resources). An excellent
introduction to the Linux USB subsystem can be found at the USB Working
Devices List (see Resources). It explains how the Linux USB subsystem is
- structured and introduces the reader to the concept of USB urbs, which
- are essential to USB drivers.
+ structured and introduces the reader to the concept of USB urbs
+ (USB Request Blocks), which are essential to USB drivers.
- When the driver is unloaded from the system, it needs to unregister
- itself with the USB subsystem. This is done with the usb_unregister
+ When the driver is unloaded from the system, it needs to deregister
+ itself with the USB subsystem. This is done with the usb_deregister
were passed to the USB subsystem will be called from a user program trying
to talk to the device. The first function called will be open, as the
program tries to open the device for I/O. We increment our private usage
were passed to the USB subsystem will be called from a user program trying
to talk to the device. The first function called will be open, as the
program tries to open the device for I/O. We increment our private usage
structure. This is done so that future calls to file operations will
enable the driver to determine which device the user is addressing. All
of this is done with the following code:
structure. This is done so that future calls to file operations will
enable the driver to determine which device the user is addressing. All
of this is done with the following code:
send to the device based on the size of the write urb it has created (this
size depends on the size of the bulk out end point that the device has).
Then it copies the data from user space to kernel space, points the urb to
send to the device based on the size of the write urb it has created (this
size depends on the size of the bulk out end point that the device has).
Then it copies the data from user space to kernel space, points the urb to