Lines Matching +full:host +full:- +full:only
11 This document presents a Linux-USB "Gadget" kernel mode API, for use
17 - Supports USB 2.0, for high speed devices which can stream data at
20 - Handles devices with dozens of endpoints just as well as ones with
21 just two fixed-function ones. Gadget drivers can be written so
24 - Flexible enough to expose more complex USB device capabilities such
28 - USB "On-The-Go" (OTG) support, in conjunction with updates to the
29 Linux-USB host side.
31 - Sharing data structures and API models with the Linux-USB host side
32 API. This helps the OTG support, and looks forward to more-symmetric
33 frameworks (where the same I/O model is used by both host and device
36 - Minimalist, so it's easier to support new device controller hardware.
41 USB ``host`` hardware in a PC, workstation, or server. Linux users with
44 Linux "USB device drivers", which are host side proxies for the real USB
50 The gadget API resembles the host side Linux-USB API in that both use
55 host side's current URB framework exposes a number of implementation
58 necessarily different (one side is a hardware-neutral master, the other
59 is a hardware-aware slave), the endpoint I/0 API used here should also
60 be usable for an overhead-reduced host side API.
74 This is the lowest software level. It is the only layer that talks
80 devices only have one upstream port, they only have one of these
82 gadget drivers, but only one of them can be used at a time.
84 Examples of such controller hardware include the PCI-based NetChip
85 2280 USB 2.0 high speed controller, the SA-11x0 or PXA-25x UDC
89 The lower boundary of this driver implements hardware-neutral USB
98 automatically for many bulk-oriented drivers.) Gadget driver
101 - handling setup requests (ep0 protocol responses) possibly
102 including class-specific functionality
104 - returning configuration and string descriptors
106 - (re)setting configurations and interface altsettings, including
109 - handling life cycle events, such as managing bindings to
111 from the USB host.
113 - managing IN and OUT transfers on all currently enabled endpoints
124 - user mode code, using generic (gadgetfs) or application specific
127 - networking subsystem (for network gadgets, like the CDC Ethernet
130 - data capture drivers, perhaps video4Linux or a scanner driver; or
133 - input subsystem (for HID gadgets)
135 - sound subsystem (for audio gadgets)
137 - file system (for PTP gadgets)
139 - block i/o subsystem (for usb-storage gadgets)
141 - ... and more
151 OTG-capable systems will also need to include a standard Linux-USB host
152 side stack, with ``usbcore``, one or more *Host Controller Drivers*
155 which is visible to gadget and device driver developers only indirectly.
156 That helps the host and device side USB controllers implement the two
157 new OTG protocols (HNP and SRP). Roles switch (host to peripheral, or
159 viewed as a more battery-friendly kind of device wakeup protocol.
167 USB-IF protocols for HID, networking, storage, or audio classes. Some
170 hardware-specific, any more than network protocols like X11, HTTP, or
171 NFS are. Such gadget-side interface drivers should eventually be
204 The core API does not expose every possible hardware feature, only the
206 such as device-to-device DMA (without temporary storage in a memory
207 buffer) that would be added using hardware-specific APIs.
213 such differences only matter for "endpoint zero" logic that handles
214 device configuration and management. The API supports limited run-time
223 Like the Linux-USB host side API, this API exposes the "chunky" nature
225 packet boundaries are visible to drivers. Compared to RS-232 serial
227 frame, multipoint addressing, host as the primary station and devices as
230 drivers won't buffer two single byte writes into a single two-byte USB
236 -----------------
246 usable (since it does not yet support enumeration). Any host should
248 used by the host to detect a device, even if VBUS power is available.
257 before the host starts to enumerate, steps before step 7 are skipped.
266 host issues a ``set_configuration`` call. It enables all endpoints used
277 device is disconnect()ed from the host. Queue any number of transfer
298 only the HNP-related differences are particularly visible to driver
304 -------------------------------------
308 Linux 2.6+ kernels. These are the same types and constants used by host side
312 ------------------------
317 .. kernel-doc:: include/linux/usb/gadget.h
321 ------------------
327 .. kernel-doc:: drivers/usb/gadget/usbstring.c
330 .. kernel-doc:: drivers/usb/gadget/config.c
334 --------------------------
338 multi-configuration devices (also more than one function, but not
349 .. kernel-doc:: include/linux/usb/composite.h
352 .. kernel-doc:: drivers/usb/gadget/composite.c
356 --------------------------
359 to this framework. Near-term plans include converting all of them,
373 "Goku-S" (``goku_udc``), Renesas SH7705/7727 (``sh_udc``), MediaQ 11xx
406 USB host as if they're an Ethernet adapter. It provides access to a
407 network where the gadget's CPU is one host, which could easily be
410 driver also implements a "good parts only" subset of CDC Ethernet. (That
428 can stream data with only slightly more overhead than a kernel driver.
431 solution for interoperability with systems such as MS-Windows and MacOS.
433 for a drive, like the ``loop`` driver. The USB host uses the BBB, CB, or
440 MS-Windows. One interesting use of that driver is in boot firmware (like
447 USB On-The-GO (OTG)
456 including a special *Mini-AB* jack and associated transceiver to support
457 *Dual-Role* operation: they can act either as a host, using the standard
458 Linux-USB host side driver stack, or as a peripheral, using this
462 connects to the OTG port. In each role, the system can re-use the
463 existing pool of hardware-neutral drivers, layered on top of the
466 support OTG can also benefit non-OTG products.
468 - Gadget drivers test the ``is_otg`` flag, and use it to determine
472 - Gadget drivers may need changes to support the two new OTG protocols,
475 suffice), and is triggered in some cases when the host suspends the
476 peripheral. SRP support can be user-initiated just like remote
479 - On the host side, USB device drivers need to be taught to trigger HNP
481 conserves battery power, which is useful even for non-OTG
484 - Also on the host side, a driver must support the OTG "Targeted
486 not supported with a given Linux OTG host. *This whitelist is
487 product-specific; each product must modify* ``otg_whitelist.h`` *to
490 Non-OTG Linux hosts, like PCs and workstations, normally have some
500 Additional changes are needed below those hardware-neutral :c:type:`usb_bus`
502 detail. Those affect the hardware-specific code for each USB Host or
504 active only on a single port). They also involve what may be called an
509 were needed inside usbcore, so that it can identify OTG-capable devices