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diff --git a/Documentation/usb/wusb-design-overview.rst b/Documentation/usb/wusb-design-overview.rst deleted file mode 100644 index dc5e21609bb5..000000000000 --- a/Documentation/usb/wusb-design-overview.rst +++ /dev/null @@ -1,457 +0,0 @@ -================================ -Linux UWB + Wireless USB + WiNET -================================ - - Copyright (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). - -.. Contents - 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) |