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Sarah Sharp
e04748e3a8
This is the original patch I created before David Vrabel posted a better patch (http://marc.info/?l=linux-usb&m=123377477209109&w=2) that does basically the same thing. This patch will get replaced with his (modified) patch later. Allow USB device drivers that use usb_sg_init() and usb_sg_wait() to push bulk endpoint scatter gather lists down to the host controller drivers. This allows host controller drivers to more efficiently enqueue these transfers, and allows the xHCI host controller to better take advantage of USB 3.0 "bursts" for bulk endpoints. This patch currently only enables scatter gather lists for bulk endpoints. Other endpoint types that use the usb_sg_* functions will not have their scatter gather lists pushed down to the host controller. For periodic endpoints, we want each scatterlist entry to be a separate transfer. Eventually, HCDs could parse these scatter-gather lists for periodic endpoints also. For now, we use the old code and call usb_submit_urb() for each scatterlist entry. The caller of usb_sg_init() can request that all bytes in the scatter gather list be transferred by passing in a length of zero. Handle that request for a bulk endpoint under xHCI by walking the scatter gather list and calculating the length. We could let the HCD handle a zero length in this case, but I'm not sure if the core layers in between will get confused by this. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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.