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ae63674714
Add URB cancellation support to the xHCI host controller driver. This currently supports cancellation for endpoints that do not have streams enabled. An URB is represented by a number of Transaction Request Buffers (TRBs), that are chained together to make one (or more) Transaction Descriptors (TDs) on an endpoint ring. The ring is comprised of contiguous segments, linked together with Link TRBs (which may or may not be chained into a TD). To cancel an URB, we must stop the endpoint ring, make the hardware skip over the TDs in the URB (either by turning them into No-op TDs, or by moving the hardware's ring dequeue pointer past the last TRB in the last TD), and then restart the ring. There are times when we must drop the xHCI lock during this process, like when we need to complete cancelled URBs. We must ensure that additional URBs can be marked as cancelled, and that new URBs can be enqueued (since the URB completion handlers can do either). The new endpoint ring variables cancels_pending and state (which can only be modified while holding the xHCI lock) ensure that future cancellation and enqueueing do not interrupt any pending cancellation code. To facilitate cancellation, we must keep track of the starting ring segment, first TRB, and last TRB for each URB. We also need to keep track of the list of TDs that have been marked as cancelled, separate from the list of TDs that are queued for this endpoint. The new variables and cancellation list are stored in the xhci_td structure. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> |
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| README | ||
| usb-skeleton.c | ||
To understand all the Linux-USB framework, you'll use these resources:
* This source code. This is necessarily an evolving work, and
includes kerneldoc that should help you get a current overview.
("make pdfdocs", and then look at "usb.pdf" for host side and
"gadget.pdf" for peripheral side.) Also, Documentation/usb has
more information.
* The USB 2.0 specification (from www.usb.org), with supplements
such as those for USB OTG and the various device classes.
The USB specification has a good overview chapter, and USB
peripherals conform to the widely known "Chapter 9".
* Chip specifications for USB controllers. Examples include
host controllers (on PCs, servers, and more); peripheral
controllers (in devices with Linux firmware, like printers or
cell phones); and hard-wired peripherals like Ethernet adapters.
* Specifications for other protocols implemented by USB peripheral
functions. Some are vendor-specific; others are vendor-neutral
but just standardized outside of the www.usb.org team.
Here is a list of what each subdirectory here is, and what is contained in
them.
core/ - This is for the core USB host code, including the
usbfs files and the hub class driver ("khubd").
host/ - This is for USB host controller drivers. This
includes UHCI, OHCI, EHCI, and others that might
be used with more specialized "embedded" systems.
gadget/ - This is for USB peripheral controller drivers and
the various gadget drivers which talk to them.
Individual USB driver directories. A new driver should be added to the
first subdirectory in the list below that it fits into.
image/ - This is for still image drivers, like scanners or
digital cameras.
../input/ - This is for any driver that uses the input subsystem,
like keyboard, mice, touchscreens, tablets, etc.
../media/ - This is for multimedia drivers, like video cameras,
radios, and any other drivers that talk to the v4l
subsystem.
../net/ - This is for network drivers.
serial/ - This is for USB to serial drivers.
storage/ - This is for USB mass-storage drivers.
class/ - This is for all USB device drivers that do not fit
into any of the above categories, and work for a range
of USB Class specified devices.
misc/ - This is for all USB device drivers that do not fit
into any of the above categories.