CSUD - Chadderz's Simple USB Driver
by Alex Chadwick
A USB driver originally written for the raspberry pi (which uses a DesignWare๏ฟฝ
Hi-Speed USB 2.0 On-The-Go (HS OTG) Controller), to be integrated into any
operating system with appropriate wrappers.
The USB standard is prohibitively long and difficult to read, and so this
driver was created to allow those working in Operating Systems development to
achieve USB support, primarily in order to gain access to the keyboard, as this
is the only sensible input on the Raspberry Pi. CSUD is designed to function
either as a standalone code section with no external dependencies, or as a more
typical driver, with external dependencies. CSUD itself is modular, and so
could have components exchanged or replaced.
CSUD is broken down into a few drivers:
* Generic USB driver (usbd) - manages parts of USB that do not change per
system, for example device enumeration and configuration. Provides
a standard interface to the environment specific host controller.
* Host Controller driver (hcd) - environment specific driver that handles
communication with the physical universal serial bus. No generic
hcd exists, instead a common header file is used for any hcd to
allow the usbd to interact in a generic way. The hcd should
translate between this interface and the physical hardware.
* DesignWare Core (dwc) driver - a specific hcd for the Synopsis DesignWare
Core host controller.
* Hub driver - driver for hubs, one of the most fundamental devices to USB.
Hubs allow multiple devices to utilise a single port, and many
devices are abstracted into hubs. The hub driver is almost
complete, lacking only features pertaining to interrupt transfers.
Built on top of the usbd.
* Human Interface Device (hid) driver - Driver supporting the generic
USB hid standard, which allows communication with logging and
sensing devices. Built on top of the usbd.
* Keyboard (kbd) driver - Driver supporting communication with keyboards.
Built on top of the hid driver, as USB keyboards are a specific
subset of hid devices. Does not have interrupt transfers, limiting
support severely (6/12 keyboards tested functioned correctly).
* Mouse driver - Driver supporting communication with mice. By Steve White.
Built on top of the hid driver, as USB mice are a specific subset
of hid devices. Does not have interrupt transfers, unknown how well
supported it is.
At present, only USB control transfers are supported by the hcd and usbd, which
is very limiting. Supporting interrupt transfers would be a major benefit, as
most devices require at least these two.
In order to achieve wider support, the /configuration has a number of makefile
include scripts which can configure the build. The overall makefile also
supports a number of arguments. The arguments are outlined in the file
arguments.
Since the driver can be standalone, the code in /source/platform.c provides an
interface to 'system' routines. Thus, it implements many methods which are
standardised, such as malloc, memcpy, free, print; though these are
deliberately not named as such. This is to avoid conflict with alternative
definitions should the need arise. Normally, it is perfectly acceptable to
write a wrapper which simply calls these functions when the equivalent is
invoked. For compatibility, print uses both the null termination convention,
and passes the length as an additional argument.
The mapping between standard methods and platform.c's version is as follows:
malloc <-> MemoryAllocate
free <-> MemoryDeallocate
memcpy <-> MemoryCopy
print <-> LogPrint
The file structure of the CSUD is as follows:
configuration/ makefile scripts for changing CSUD's build configuration.
include/ included header files.
device/ header files for device drivers
hid/ header files for human interface devices.
hcd/ header files for the host controller driver.
dwc/ header files for the DesignWare core.
platform/ header files for the system CSUD runs in.
arm/ header files for ARM platforms.
none/ header files for generic platforms.
usbd/ header files for the generic USB driver.
source/ source code files.
device/ source code for device drivers
hid/ source code for human interface device drivers.
hcd/ source code for the host controller driver
dwc/ source code for the DesignWare host controller
platform/ source code for the system CSUD runs in.
arm/ source code for ARM platforms.
usbd/ source code for the generic USB driver.
