mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-11-19 11:18:28 +00:00
15c6935b0c
This patch contains UDM-design.txt, which is document containing general description of the driver model. The remaining files contains descriptions of conversion process of particular subsystems. Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
94 lines
3.6 KiB
Text
94 lines
3.6 KiB
Text
The U-Boot Driver Model Project
|
|
===============================
|
|
USB analysis
|
|
============
|
|
Marek Vasut <marek.vasut@gmail.com>
|
|
2012-02-16
|
|
|
|
I) Overview
|
|
-----------
|
|
|
|
1) The USB Host driver
|
|
----------------------
|
|
There are basically four or five USB host drivers. All such drivers currently
|
|
provide at least the following fuctions:
|
|
|
|
usb_lowlevel_init() ... Do the initialization of the USB controller hardware
|
|
usb_lowlevel_stop() ... Do the shutdown of the USB controller hardware
|
|
|
|
usb_event_poll() ...... Poll interrupt from USB device, often used by KBD
|
|
|
|
submit_control_msg() .. Submit message via Control endpoint
|
|
submit_int_msg() ...... Submit message via Interrupt endpoint
|
|
submit_bulk_msg() ..... Submit message via Bulk endpoint
|
|
|
|
|
|
This allows for the host driver to be easily abstracted.
|
|
|
|
2) The USB hierarchy
|
|
--------------------
|
|
|
|
In the current implementation, the USB Host driver provides operations to
|
|
communicate via the USB bus. This is realised by providing access to a USB
|
|
root port to which an USB root hub is attached. The USB bus is scanned and for
|
|
each newly found device, a struct usb_device is allocated. See common/usb.c
|
|
and include/usb.h for details.
|
|
|
|
II) Approach
|
|
------------
|
|
|
|
1) The USB Host driver
|
|
----------------------
|
|
|
|
Converting the host driver will follow the classic driver model consideration.
|
|
Though, the host driver will have to call a function that registers a root
|
|
port with the USB core in it's probe() function, let's call this function
|
|
|
|
usb_register_root_port(&ops);
|
|
|
|
This will allow the USB core to track all available root ports. The ops
|
|
parameter will contain structure describing operations supported by the root
|
|
port:
|
|
|
|
struct usb_port_ops {
|
|
void (*usb_event_poll)();
|
|
int (*submit_control_msg)();
|
|
int (*submit_int_msg)();
|
|
int (*submit_bulk_msg)();
|
|
}
|
|
|
|
2) The USB hierarchy and hub drivers
|
|
------------------------------------
|
|
|
|
Converting the USB heirarchy should be fairy simple, considering the already
|
|
dynamic nature of the implementation. The current usb_hub_device structure
|
|
will have to be converted to a struct instance. Every such instance will
|
|
contain components of struct usb_device and struct usb_hub_device in it's
|
|
private data, providing only accessors in order to properly encapsulate the
|
|
driver.
|
|
|
|
By registering the root port, the USB framework will instantiate a USB hub
|
|
driver, which is always present, the root hub. The root hub and any subsequent
|
|
hub instance is represented by struct instance and it's private data contain
|
|
amongst others common bits from struct usb_device.
|
|
|
|
Note the USB hub driver is partly defying the usual method of registering a
|
|
set of callbacks to a particular core driver. Instead, a static set of
|
|
functions is defined and the USB hub instance is passed to those. This creates
|
|
certain restrictions as of how the USB hub driver looks, but considering the
|
|
specification for USB hub is given and a different type of USB hub won't ever
|
|
exist, this approach is ok:
|
|
|
|
- Report how many ports does this hub have:
|
|
uint get_nr_ports(struct instance *hub);
|
|
- Get pointer to device connected to a port:
|
|
struct instance *(*get_child)(struct instance *hub, int port);
|
|
- Instantiate and configure device on port:
|
|
struct instance *(*enum_dev_on_port)(struct instance *hub, int port);
|
|
|
|
3) USB device drivers
|
|
---------------------
|
|
|
|
The USB device driver, in turn, will have to register various ops structures
|
|
with certain cores. For example, USB disc driver will have to register it's
|
|
ops with core handling USB discs etc.
|