mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-05 10:04:12 +08:00
37ebb54915
USB hub has started to use a workqueue instead of kthread. Let's update the documentation and comments here and there. This patch mostly just replaces "khubd" with "hub_wq". There are only few exceptions where the whole sentence was updated. These more complicated changes can be found in the following files: Documentation/usb/hotplug.txt drivers/net/usb/usbnet.c drivers/usb/core/hcd.c drivers/usb/host/ohci-hcd.c drivers/usb/host/xhci.c Signed-off-by: Petr Mladek <pmladek@suse.cz> Acked-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
440 lines
18 KiB
Plaintext
440 lines
18 KiB
Plaintext
|
|
Linux UWB + Wireless USB + WiNET
|
|
|
|
(C) 2005-2006 Intel Corporation
|
|
Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
|
|
|
|
This program is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU General Public License version
|
|
2 as published by the Free Software Foundation.
|
|
|
|
This program is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with this program; if not, write to the Free Software
|
|
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
|
|
02110-1301, USA.
|
|
|
|
|
|
Please visit http://bughost.org/thewiki/Design-overview.txt-1.8 for
|
|
updated content.
|
|
|
|
* Design-overview.txt-1.8
|
|
|
|
This code implements a Ultra Wide Band stack for Linux, as well as
|
|
drivers for the USB based UWB radio controllers defined in the
|
|
Wireless USB 1.0 specification (including Wireless USB host controller
|
|
and an Intel WiNET controller).
|
|
|
|
1. Introduction
|
|
1. HWA: Host Wire adapters, your Wireless USB dongle
|
|
|
|
2. DWA: Device Wired Adaptor, a Wireless USB hub for wired
|
|
devices
|
|
3. WHCI: Wireless Host Controller Interface, the PCI WUSB host
|
|
adapter
|
|
2. The UWB stack
|
|
1. Devices and hosts: the basic structure
|
|
|
|
2. Host Controller life cycle
|
|
|
|
3. On the air: beacons and enumerating the radio neighborhood
|
|
|
|
4. Device lists
|
|
5. Bandwidth allocation
|
|
|
|
3. Wireless USB Host Controller drivers
|
|
|
|
4. Glossary
|
|
|
|
|
|
Introduction
|
|
|
|
UWB is a wide-band communication protocol that is to serve also as the
|
|
low-level protocol for others (much like TCP sits on IP). Currently
|
|
these others are Wireless USB and TCP/IP, but seems Bluetooth and
|
|
Firewire/1394 are coming along.
|
|
|
|
UWB uses a band from roughly 3 to 10 GHz, transmitting at a max of
|
|
~-41dB (or 0.074 uW/MHz--geography specific data is still being
|
|
negotiated w/ regulators, so watch for changes). That band is divided in
|
|
a bunch of ~1.5 GHz wide channels (or band groups) composed of three
|
|
subbands/subchannels (528 MHz each). Each channel is independent of each
|
|
other, so you could consider them different "busses". Initially this
|
|
driver considers them all a single one.
|
|
|
|
Radio time is divided in 65536 us long /superframes/, each one divided
|
|
in 256 256us long /MASs/ (Media Allocation Slots), which are the basic
|
|
time/media allocation units for transferring data. At the beginning of
|
|
each superframe there is a Beacon Period (BP), where every device
|
|
transmit its beacon on a single MAS. The length of the BP depends on how
|
|
many devices are present and the length of their beacons.
|
|
|
|
Devices have a MAC (fixed, 48 bit address) and a device (changeable, 16
|
|
bit address) and send periodic beacons to advertise themselves and pass
|
|
info on what they are and do. They advertise their capabilities and a
|
|
bunch of other stuff.
|
|
|
|
The different logical parts of this driver are:
|
|
|
|
*
|
|
|
|
*UWB*: the Ultra-Wide-Band stack -- manages the radio and
|
|
associated spectrum to allow for devices sharing it. Allows to
|
|
control bandwidth assignment, beaconing, scanning, etc
|
|
|
|
*
|
|
|
|
*WUSB*: the layer that sits on top of UWB to provide Wireless USB.
|
|
The Wireless USB spec defines means to control a UWB radio and to
|
|
do the actual WUSB.
|
|
|
|
|
|
HWA: Host Wire adapters, your Wireless USB dongle
|
|
|
|
WUSB also defines a device called a Host Wire Adaptor (HWA), which in
|
|
mere terms is a USB dongle that enables your PC to have UWB and Wireless
|
|
USB. The Wireless USB Host Controller in a HWA looks to the host like a
|
|
[Wireless] USB controller connected via USB (!)
|
|
|
|
The HWA itself is broken in two or three main interfaces:
|
|
|
|
*
|
|
|
|
*RC*: Radio control -- this implements an interface to the
|
|
Ultra-Wide-Band radio controller. The driver for this implements a
|
|
USB-based UWB Radio Controller to the UWB stack.
|
|
|
|
*
|
|
|
|
*HC*: the wireless USB host controller. It looks like a USB host
|
|
whose root port is the radio and the WUSB devices connect to it.
|
|
To the system it looks like a separate USB host. The driver (will)
|
|
implement a USB host controller (similar to UHCI, OHCI or EHCI)
|
|
for which the root hub is the radio...To reiterate: it is a USB
|
|
controller that is connected via USB instead of PCI.
|
|
|
|
*
|
|
|
|
*WINET*: some HW provide a WiNET interface (IP over UWB). This
|
|
package provides a driver for it (it looks like a network
|
|
interface, winetX). The driver detects when there is a link up for
|
|
their type and kick into gear.
|
|
|
|
|
|
DWA: Device Wired Adaptor, a Wireless USB hub for wired devices
|
|
|
|
These are the complement to HWAs. They are a USB host for connecting
|
|
wired devices, but it is connected to your PC connected via Wireless
|
|
USB. To the system it looks like yet another USB host. To the untrained
|
|
eye, it looks like a hub that connects upstream wirelessly.
|
|
|
|
We still offer no support for this; however, it should share a lot of
|
|
code with the HWA-RC driver; there is a bunch of factorization work that
|
|
has been done to support that in upcoming releases.
|
|
|
|
|
|
WHCI: Wireless Host Controller Interface, the PCI WUSB host adapter
|
|
|
|
This is your usual PCI device that implements WHCI. Similar in concept
|
|
to EHCI, it allows your wireless USB devices (including DWAs) to connect
|
|
to your host via a PCI interface. As in the case of the HWA, it has a
|
|
Radio Control interface and the WUSB Host Controller interface per se.
|
|
|
|
There is still no driver support for this, but will be in upcoming
|
|
releases.
|
|
|
|
|
|
The UWB stack
|
|
|
|
The main mission of the UWB stack is to keep a tally of which devices
|
|
are in radio proximity to allow drivers to connect to them. As well, it
|
|
provides an API for controlling the local radio controllers (RCs from
|
|
now on), such as to start/stop beaconing, scan, allocate bandwidth, etc.
|
|
|
|
|
|
Devices and hosts: the basic structure
|
|
|
|
The main building block here is the UWB device (struct uwb_dev). For
|
|
each device that pops up in radio presence (ie: the UWB host receives a
|
|
beacon from it) you get a struct uwb_dev that will show up in
|
|
/sys/bus/uwb/devices.
|
|
|
|
For each RC that is detected, a new struct uwb_rc and struct uwb_dev are
|
|
created. An entry is also created in /sys/class/uwb_rc for each RC.
|
|
|
|
Each RC driver is implemented by a separate driver that plugs into the
|
|
interface that the UWB stack provides through a struct uwb_rc_ops. The
|
|
spec creators have been nice enough to make the message format the same
|
|
for HWA and WHCI RCs, so the driver is really a very thin transport that
|
|
moves the requests from the UWB API to the device [/uwb_rc_ops->cmd()/]
|
|
and sends the replies and notifications back to the API
|
|
[/uwb_rc_neh_grok()/]. Notifications are handled to the UWB daemon, that
|
|
is chartered, among other things, to keep the tab of how the UWB radio
|
|
neighborhood looks, creating and destroying devices as they show up or
|
|
disappear.
|
|
|
|
Command execution is very simple: a command block is sent and a event
|
|
block or reply is expected back. For sending/receiving command/events, a
|
|
handle called /neh/ (Notification/Event Handle) is opened with
|
|
/uwb_rc_neh_open()/.
|
|
|
|
The HWA-RC (USB dongle) driver (drivers/uwb/hwa-rc.c) does this job for
|
|
the USB connected HWA. Eventually, drivers/whci-rc.c will do the same
|
|
for the PCI connected WHCI controller.
|
|
|
|
|
|
Host Controller life cycle
|
|
|
|
So let's say we connect a dongle to the system: it is detected and
|
|
firmware uploaded if needed [for Intel's i1480
|
|
/drivers/uwb/ptc/usb.c:ptc_usb_probe()/] and then it is reenumerated.
|
|
Now we have a real HWA device connected and
|
|
/drivers/uwb/hwa-rc.c:hwarc_probe()/ picks it up, that will set up the
|
|
Wire-Adaptor environment and then suck it into the UWB stack's vision of
|
|
the world [/drivers/uwb/lc-rc.c:uwb_rc_add()/].
|
|
|
|
*
|
|
|
|
[*] The stack should put a new RC to scan for devices
|
|
[/uwb_rc_scan()/] so it finds what's available around and tries to
|
|
connect to them, but this is policy stuff and should be driven
|
|
from user space. As of now, the operator is expected to do it
|
|
manually; see the release notes for documentation on the procedure.
|
|
|
|
When a dongle is disconnected, /drivers/uwb/hwa-rc.c:hwarc_disconnect()/
|
|
takes time of tearing everything down safely (or not...).
|
|
|
|
|
|
On the air: beacons and enumerating the radio neighborhood
|
|
|
|
So assuming we have devices and we have agreed for a channel to connect
|
|
on (let's say 9), we put the new RC to beacon:
|
|
|
|
*
|
|
|
|
$ echo 9 0 > /sys/class/uwb_rc/uwb0/beacon
|
|
|
|
Now it is visible. If there were other devices in the same radio channel
|
|
and beacon group (that's what the zero is for), the dongle's radio
|
|
control interface will send beacon notifications on its
|
|
notification/event endpoint (NEEP). The beacon notifications are part of
|
|
the event stream that is funneled into the API with
|
|
/drivers/uwb/neh.c:uwb_rc_neh_grok()/ and delivered to the UWBD, the UWB
|
|
daemon through a notification list.
|
|
|
|
UWBD wakes up and scans the event list; finds a beacon and adds it to
|
|
the BEACON CACHE (/uwb_beca/). If he receives a number of beacons from
|
|
the same device, he considers it to be 'onair' and creates a new device
|
|
[/drivers/uwb/lc-dev.c:uwbd_dev_onair()/]. Similarly, when no beacons
|
|
are received in some time, the device is considered gone and wiped out
|
|
[uwbd calls periodically /uwb/beacon.c:uwb_beca_purge()/ that will purge
|
|
the beacon cache of dead devices].
|
|
|
|
|
|
Device lists
|
|
|
|
All UWB devices are kept in the list of the struct bus_type uwb_bus_type.
|
|
|
|
|
|
Bandwidth allocation
|
|
|
|
The UWB stack maintains a local copy of DRP availability through
|
|
processing of incoming *DRP Availability Change* notifications. This
|
|
local copy is currently used to present the current bandwidth
|
|
availability to the user through the sysfs file
|
|
/sys/class/uwb_rc/uwbx/bw_avail. In the future the bandwidth
|
|
availability information will be used by the bandwidth reservation
|
|
routines.
|
|
|
|
The bandwidth reservation routines are in progress and are thus not
|
|
present in the current release. When completed they will enable a user
|
|
to initiate DRP reservation requests through interaction with sysfs. DRP
|
|
reservation requests from remote UWB devices will also be handled. The
|
|
bandwidth management done by the UWB stack will include callbacks to the
|
|
higher layers will enable the higher layers to use the reservations upon
|
|
completion. [Note: The bandwidth reservation work is in progress and
|
|
subject to change.]
|
|
|
|
|
|
Wireless USB Host Controller drivers
|
|
|
|
*WARNING* This section needs a lot of work!
|
|
|
|
As explained above, there are three different types of HCs in the WUSB
|
|
world: HWA-HC, DWA-HC and WHCI-HC.
|
|
|
|
HWA-HC and DWA-HC share that they are Wire-Adapters (USB or WUSB
|
|
connected controllers), and their transfer management system is almost
|
|
identical. So is their notification delivery system.
|
|
|
|
HWA-HC and WHCI-HC share that they are both WUSB host controllers, so
|
|
they have to deal with WUSB device life cycle and maintenance, wireless
|
|
root-hub
|
|
|
|
HWA exposes a Host Controller interface (HWA-HC 0xe0/02/02). This has
|
|
three endpoints (Notifications, Data Transfer In and Data Transfer
|
|
Out--known as NEP, DTI and DTO in the code).
|
|
|
|
We reserve UWB bandwidth for our Wireless USB Cluster, create a Cluster
|
|
ID and tell the HC to use all that. Then we start it. This means the HC
|
|
starts sending MMCs.
|
|
|
|
*
|
|
|
|
The MMCs are blocks of data defined somewhere in the WUSB1.0 spec
|
|
that define a stream in the UWB channel time allocated for sending
|
|
WUSB IEs (host to device commands/notifications) and Device
|
|
Notifications (device initiated to host). Each host defines a
|
|
unique Wireless USB cluster through MMCs. Devices can connect to a
|
|
single cluster at the time. The IEs are Information Elements, and
|
|
among them are the bandwidth allocations that tell each device
|
|
when can they transmit or receive.
|
|
|
|
Now it all depends on external stimuli.
|
|
|
|
*New device connection*
|
|
|
|
A new device pops up, it scans the radio looking for MMCs that give out
|
|
the existence of Wireless USB channels. Once one (or more) are found,
|
|
selects which one to connect to. Sends a /DN_Connect/ (device
|
|
notification connect) during the DNTS (Device Notification Time
|
|
Slot--announced in the MMCs
|
|
|
|
HC picks the /DN_Connect/ out (nep module sends to notif.c for delivery
|
|
into /devconnect/). This process starts the authentication process for
|
|
the device. First we allocate a /fake port/ and assign an
|
|
unauthenticated address (128 to 255--what we really do is
|
|
0x80 | fake_port_idx). We fiddle with the fake port status and /hub_wq/
|
|
sees a new connection, so he moves on to enable the fake port with a reset.
|
|
|
|
So now we are in the reset path -- we know we have a non-yet enumerated
|
|
device with an unauthorized address; we ask user space to authenticate
|
|
(FIXME: not yet done, similar to bluetooth pairing), then we do the key
|
|
exchange (FIXME: not yet done) and issue a /set address 0/ to bring the
|
|
device to the default state. Device is authenticated.
|
|
|
|
From here, the USB stack takes control through the usb_hcd ops. hub_wq
|
|
has seen the port status changes, as we have been toggling them. It will
|
|
start enumerating and doing transfers through usb_hcd->urb_enqueue() to
|
|
read descriptors and move our data.
|
|
|
|
*Device life cycle and keep alives*
|
|
|
|
Every time there is a successful transfer to/from a device, we update a
|
|
per-device activity timestamp. If not, every now and then we check and
|
|
if the activity timestamp gets old, we ping the device by sending it a
|
|
Keep Alive IE; it responds with a /DN_Alive/ pong during the DNTS (this
|
|
arrives to us as a notification through
|
|
devconnect.c:wusb_handle_dn_alive(). If a device times out, we
|
|
disconnect it from the system (cleaning up internal information and
|
|
toggling the bits in the fake hub port, which kicks hub_wq into removing
|
|
the rest of the stuff).
|
|
|
|
This is done through devconnect:__wusb_check_devs(), which will scan the
|
|
device list looking for whom needs refreshing.
|
|
|
|
If the device wants to disconnect, it will either die (ugly) or send a
|
|
/DN_Disconnect/ that will prompt a disconnection from the system.
|
|
|
|
*Sending and receiving data*
|
|
|
|
Data is sent and received through /Remote Pipes/ (rpipes). An rpipe is
|
|
/aimed/ at an endpoint in a WUSB device. This is the same for HWAs and
|
|
DWAs.
|
|
|
|
Each HC has a number of rpipes and buffers that can be assigned to them;
|
|
when doing a data transfer (xfer), first the rpipe has to be aimed and
|
|
prepared (buffers assigned), then we can start queueing requests for
|
|
data in or out.
|
|
|
|
Data buffers have to be segmented out before sending--so we send first a
|
|
header (segment request) and then if there is any data, a data buffer
|
|
immediately after to the DTI interface (yep, even the request). If our
|
|
buffer is bigger than the max segment size, then we just do multiple
|
|
requests.
|
|
|
|
[This sucks, because doing USB scatter gatter in Linux is resource
|
|
intensive, if any...not that the current approach is not. It just has to
|
|
be cleaned up a lot :)].
|
|
|
|
If reading, we don't send data buffers, just the segment headers saying
|
|
we want to read segments.
|
|
|
|
When the xfer is executed, we receive a notification that says data is
|
|
ready in the DTI endpoint (handled through
|
|
xfer.c:wa_handle_notif_xfer()). In there we read from the DTI endpoint a
|
|
descriptor that gives us the status of the transfer, its identification
|
|
(given when we issued it) and the segment number. If it was a data read,
|
|
we issue another URB to read into the destination buffer the chunk of
|
|
data coming out of the remote endpoint. Done, wait for the next guy. The
|
|
callbacks for the URBs issued from here are the ones that will declare
|
|
the xfer complete at some point and call its callback.
|
|
|
|
Seems simple, but the implementation is not trivial.
|
|
|
|
*
|
|
|
|
*WARNING* Old!!
|
|
|
|
The main xfer descriptor, wa_xfer (equivalent to a URB) contains an
|
|
array of segments, tallys on segments and buffers and callback
|
|
information. Buried in there is a lot of URBs for executing the segments
|
|
and buffer transfers.
|
|
|
|
For OUT xfers, there is an array of segments, one URB for each, another
|
|
one of buffer URB. When submitting, we submit URBs for segment request
|
|
1, buffer 1, segment 2, buffer 2...etc. Then we wait on the DTI for xfer
|
|
result data; when all the segments are complete, we call the callback to
|
|
finalize the transfer.
|
|
|
|
For IN xfers, we only issue URBs for the segments we want to read and
|
|
then wait for the xfer result data.
|
|
|
|
*URB mapping into xfers*
|
|
|
|
This is done by hwahc_op_urb_[en|de]queue(). In enqueue() we aim an
|
|
rpipe to the endpoint where we have to transmit, create a transfer
|
|
context (wa_xfer) and submit it. When the xfer is done, our callback is
|
|
called and we assign the status bits and release the xfer resources.
|
|
|
|
In dequeue() we are basically cancelling/aborting the transfer. We issue
|
|
a xfer abort request to the HC, cancel all the URBs we had submitted
|
|
and not yet done and when all that is done, the xfer callback will be
|
|
called--this will call the URB callback.
|
|
|
|
|
|
Glossary
|
|
|
|
*DWA* -- Device Wire Adapter
|
|
|
|
USB host, wired for downstream devices, upstream connects wirelessly
|
|
with Wireless USB.
|
|
|
|
*EVENT* -- Response to a command on the NEEP
|
|
|
|
*HWA* -- Host Wire Adapter / USB dongle for UWB and Wireless USB
|
|
|
|
*NEH* -- Notification/Event Handle
|
|
|
|
Handle/file descriptor for receiving notifications or events. The WA
|
|
code requires you to get one of this to listen for notifications or
|
|
events on the NEEP.
|
|
|
|
*NEEP* -- Notification/Event EndPoint
|
|
|
|
Stuff related to the management of the first endpoint of a HWA USB
|
|
dongle that is used to deliver an stream of events and notifications to
|
|
the host.
|
|
|
|
*NOTIFICATION* -- Message coming in the NEEP as response to something.
|
|
|
|
*RC* -- Radio Control
|
|
|
|
Design-overview.txt-1.8 (last edited 2006-11-04 12:22:24 by
|
|
InakyPerezGonzalez)
|
|
|