linux/drivers/usb
Alan Stern c3ee9b76aa EHCI: improved logic for isochronous scheduling
This patch (as1608) reworks the logic used by ehci-hcd for scheduling
isochronous transfers.  Now the modular calculations are all based on
a window that starts at the last frame scanned for isochronous
completions.  No transfer descriptors for any earlier frames can
possibly remain on the schedule, so there can be no confusion from
schedule wrap-around.  This removes the need for a "slop" region of
arbitrary size.

There's no need to check for URBs that are longer than the schedule
length.  With the old code they could throw things off by wrapping
around and appearing to end in the near future rather than the distant
future.  Now such confusion isn't possible, and the existing test for
submissions that extend too far into the future will also catch those
that exceed the schedule length.  (But there still has to be an
initial test to handle the case where the schedule already extends as
far into the future as possible.)

Delays caused by IRQ latency won't confuse the algorithm unless they
are ridiculously long (over 250 ms); they will merely reduce how far
into the future new transfers can be scheduled.  A few people have
reported problems caused by delays of 50 ms or so.  Now instead of
failing completely, isochronous transfers will experience a brief
glitch and then continue normally.

(Whether this is truly a good thing is debatable.  A latency as large
as 50 ms generally indicates a bug is present, and complete failure of
audio or video transfers draws people's attention pretty vividly.
Making the transfers more robust also makes it easier for such bugs to
remain undetected.)

Finally, ehci->next_frame is renamed to ehci->last_iso_frame, because
that better describes what it is: the last frame to have been scanned
for isochronous completions.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-10-22 08:57:43 -07:00
..
atm Merge branch 'for-3.7' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2012-10-02 09:54:49 -07:00
c67x00
chipidea USB: chipidea: re-order irq handling to avoid unhandled irqs 2012-09-12 11:20:38 -07:00
class usb: acm: fix the computation of the number of data bits 2012-10-17 13:45:49 -07:00
core usbdevfs: Fix broken scatter-gather transfer 2012-10-17 13:41:34 -07:00
dwc3 usb: dwc3: shutdown usb_phy when removing the device 2012-10-15 16:25:23 +03:00
early USB EHCI/Xen: propagate controller reset information to hypervisor 2012-09-18 17:20:48 +01:00
gadget usb: fixes for v3.7-rc2 2012-10-18 08:14:10 -07:00
host EHCI: improved logic for isochronous scheduling 2012-10-22 08:57:43 -07:00
image
misc USB: ezusb: move ezusb.c from drivers/usb/serial to drivers/usb/misc 2012-09-26 14:20:28 -07:00
mon mm: kill vma flag VM_RESERVED and mm->reserved_vm counter 2012-10-09 16:22:19 +09:00
musb usb: musb: am35xx: drop spurious unplugging a device 2012-10-15 15:20:27 +03:00
otg Merge branch 'for-3.7' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq 2012-10-02 09:54:49 -07:00
phy ARM: tegra: remove useless includes of <mach/*.h> 2012-09-14 11:35:36 -06:00
renesas_usbhs usb: renesas_usbhs: fixup interrupt status clear method 2012-10-16 12:47:40 +03:00
serial USB: option: add more ZTE devices 2012-10-18 08:27:21 -07:00
storage USB: uas: fix gcc warning 2012-09-26 14:13:19 -07:00
wusbcore USB: remove CONFIG_EXPERIMENTAL dependancies 2012-09-17 23:00:15 -07:00
Kconfig ARM: soc: general cleanups 2012-10-01 18:19:05 -07:00
Makefile
README
usb-common.c
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.