linux-sg2042/drivers/usb
Alan Stern 8ef42ddd9a USB: Avoid runtime suspend loops for HCDs that can't handle suspend/resume
Not all host controller drivers have bus-suspend and bus-resume
methods.  When one doesn't, it will cause problems if runtime PM is
enabled in the kernel.  The PM core will attempt to suspend the
controller's root hub, the suspend will fail because there is no
bus-suspend routine, and a -EBUSY error code will be returned to the
PM core.  This will cause the suspend attempt to be repeated shortly
thereafter, in a never-ending loop.

Part of the problem is that the original error code -ENOENT gets
changed to -EBUSY in usb_runtime_suspend(), on the grounds that the PM
core will interpret -ENOENT as meaning that the root hub has gotten
into a runtime-PM error state.  While this change is appropriate for
real USB devices, it's not such a good idea for a root hub.  In fact,
considering the root hub to be in a runtime-PM error state would not
be far from the truth.  Therefore this patch updates
usb_runtime_suspend() so that it adjusts error codes only for
non-root-hub devices.

Furthermore, the patch attempts to prevent the problem from occurring
in the first place by not enabling runtime PM by default for root hubs
whose host controller driver doesn't have bus_suspend and bus_resume
methods.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Will Deacon <will.deacon@arm.com>
Tested-by: Will Deacon <will.deacon@arm.com>
CC: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-05-24 04:06:00 +09:00
..
atm usb: delete non-required instances of include <linux/init.h> 2014-01-08 15:01:39 -08:00
c67x00 USB: c67x00: correct spelling mistakes in comments 2014-01-08 15:05:14 -08:00
chipidea usb: chipidea: coordinate usb phy initialization for different phy type 2014-04-24 12:45:40 -07:00
class USB: cdc-acm: Remove Motorola/Telit H24 serial interfaces from ACM driver 2014-04-16 14:03:40 -07:00
core USB: Avoid runtime suspend loops for HCDs that can't handle suspend/resume 2014-05-24 04:06:00 +09:00
dwc2 usb: dwc2: fix dereference before NULL check 2014-02-15 12:26:14 -08:00
dwc3 usb: dwc3: core: Fix gadget for system suspend/resume 2014-04-16 10:11:45 -05:00
early USB: ehci-dbgp: drop dead code. 2013-09-26 16:25:21 -07:00
gadget usb: gadget: at91-udc: fix irq and iomem resource retrieval 2014-04-30 11:59:06 -05:00
host fsl-usb: do not test for PHY_CLK_VALID bit on controller version 1.6 2014-05-03 18:04:28 -04:00
image USB: image: correct spelling mistake in comment 2014-01-08 15:08:14 -08:00
misc USB: sisusb: Use static const, fix typo 2014-03-03 08:54:30 -08:00
mon USB: regroup all depends on USB within an if USB block 2013-04-09 16:49:07 -07:00
musb usb: musb: dsps: move debugfs_remove_recursive() 2014-04-16 10:11:46 -05:00
phy usb: phy: fsm: change "|" to "||" for condition OTG_STATE_A_WAIT_BCON at statemachine 2014-04-24 09:54:32 -05:00
renesas_usbhs usb: changes for v3.14 merge window 2014-01-03 12:15:10 -08:00
serial usb: qcserial: add a number of Dell devices 2014-05-03 18:04:28 -04:00
storage USB: Nokia 5300 should be treated as unusual dev 2014-05-03 19:41:07 -04:00
wusbcore usb: wusbcore: fix panic in wusbhc_chid_set 2014-04-24 12:45:41 -07:00
Kconfig usb: host: remove USB_ARCH_HAS_?HCI 2014-02-18 12:36:38 -08:00
Makefile Move DWC2 driver out of staging 2014-01-13 14:44:01 -08:00
README
usb-common.c usb: usb-common: fix typo for usb_state_string 2014-04-16 13:56:08 -07:00
usb-skeleton.c usb: delete non-required instances of include <linux/init.h> 2014-01-08 15:01:39 -08:00

README

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.