Pass value instead of address as expected by 'usb_ep_set_maxpacket_limit'.
Fixes the following compilation error introduced by commit e117e742
("usb: gadget: add "maxpacket_limit" field to struct usb_ep"):

drivers/usb/gadget/s3c2410_udc.c: In function ‘s3c2410_udc_reinit’:
drivers/usb/gadget/s3c2410_udc.c:1632:3: error:
cannot take address of bit-field ‘maxpacket’
   usb_ep_set_maxpacket_limit(&ep->ep, &ep->ep.maxpacket);
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Reviewed-by: Robert Baldyga <r.baldyga@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

Set the return variable to an error code as done elsewhere in the function.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
(
if@p1 (\(ret < 0\|ret != 0\))
 { ... return ret; }
|
ret@p1 = 0
)
... when != ret = e1
    when != &ret
*if(...)
{
  ... when != ret = e2
      when forall
 return ret;
}

// </smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Felipe Balbi <balbi@ti.com>

Use %pad for dma_addr_t to avoid the following build warnings
in printks.

drivers/usb/gadget/s3c-hsotg.c: In function 's3c_hsotg_start_req'
drivers/usb/gadget/s3c-hsotg.c:722:3: warning: format '%x' expects argument of type 'unsigned int' but argument 6 has type
'dma_addr_t' [-Wformat]
drivers/usb/gadget/s3c-hsotg.c:792:3: warning: format '%x' expects argument of type 'unsigned int' but argument 5 has type
'dma_addr_t' [-Wformat]
Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

The readsl and writesl I/O accessors are only defined on some
architectures. The driver currently depends on CONFIG_ARM because
the build breaks on x86, in particular. Switch to use of ioread32_rep
and iowrite32_rep to fix build on all architectures and remove the
CONFIG_ARM dependency.

Also update printk formatting to handle a long long dma_addr_t to avoid
warnings on !32-bit architectures.
Signed-off-by: Matt Porter <mporter@linaro.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>

In case of ISOCH transfers the hrtimer workaround for the hardware issue
is not very reliable. Instead of checking musb_is_tx_fifo_empty() in hrtimer
routine, schedule a completion work and check the same in completion work.
Signed-off-by: George Cherian <george.cherian@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

Enable CPPI to handle high bandwidth transfers, especially to support
webcam captures. Use a single bd to get the whole of the data in case of
high bandwidth transfers.
Signed-off-by: George Cherian <george.cherian@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

Enable the isochrounous IN handling for AM335x HOST.
Reprogram CPPI to receive consecutive ISOCH frames in the same URB.
Signed-off-by: George Cherian <george.cherian@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

include/phy/phy.h has stub code in there for when building without the
phy-core enabled. This is useful for generic drivers such as ahci-platform,
ehci-platoform and ohci-platform which have support for driving an optional
phy passed to them through the devicetree.

Since on some boards this phy functionality is not needed, being able to
disable the phy subsystem without needing a lot of #ifdef magic in the
driver using it is quite useful.

However this breaks when the module using the phy subsystem is build-in and
the phy-core is not, which leads to the build failing with missing symbol
errors in the linking stage of the zImage.

Which leads to gems such as this being added to the Kconfig for achi_platform:

	depends on GENERIC_PHY || !GENERIC_PHY

Rather then duplicating this code in a lot of places using the phy-core,
I believe it is better to simply not allow the phy-core to be built as a
module. The phy core is quite small and has no external dependencies, so
always building it in when enabling it should not be an issue.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The "Webmail Notifier" is a USB controlled LED that appears as a HID
device. When trying to change the LED via hidraw it returns malformed
reports. As "usbled" supports it, we blacklist it in usbhid.
Signed-off-by: Christian Vogel <vogelchr@vogel.cx>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

In a couple of places, we were checking qtd->urb for NULL after
we had already dereferenced it. Fix this by moving the check to
before the dereference.
Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This brings the xhci-platform bindings in sync with what we've done for
the ohci- and ehci-platform drivers. As discussed there using platform as a
postfix is a bit weird as the platform bus is a Linux specific thing and
the bindings are supposed to be OS agnostic.

Note that the old xhci-platform compatible string is kept around for, well,
compatibility reasons.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This brings the uhci-platform bindings in sync with what we've done for
the ohci- and ehci-platform drivers. As discussed there using platform as a
prefix is a bit weird as the platform bus is a Linux specific thing and
the bindings are supposed to be OS agnostic.

Note that the old platform-uhci compatible string is kept around for, well,
compatibility reasons.

While at it rename the bindings txt file to match the name of all the
other ?hci-platform bindings docs.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Add support for the "Webmail Notifier" (USB powered LED for signaling
new emails) made by Riso Kagaku Corp. which displays 7 distinct colors.

USB Protocol initially reverse engineered by
	https://code.google.com/p/usbmailnotifier/.
Signed-off-by: Christian Vogel <vogelchr@vogel.cx>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The Kconfig entries for USB_U132_HCD and USB_FTDI_ELAN default to
(uppercase) "M". But in Kconfig (lowercase) "m" is a magic symbol. "M"
is an ordinary symbol. As "M" is never set these Kconfig symbols will
also not be set by default.

Since I'm not aware of a reason why these driver should be set by
default, let's just drop these lines (that basically do nothing).
Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The symbol is an orphan, get rid of it.
Signed-off-by: Richard Weinberger <richard@nod.at>
Acked-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The ohci-platform driver checks for misconfigurations in cases where
the Device Tree data specifies big-endian registers or descriptors but
the corresponding driver config settings have not been enabled.  As
Jonas Gorski suggested, we may as well apply the same check to general
platform data too.

This requires moving the code that sets the big-endian quirk flags
from the ohci_platform_reset() routine into ohci_platform_probe(), and
moving the checks out of the DT-specific "if" statement clause.

The patch also changes the text of the error messages in an attempt to
make the nature of the error more clear.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Jonas Gorski <jogo@openwrt.org>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The ehci-platform driver checks for misconfigurations in cases where
the Device Tree data specifies big-endian registers or descriptors but
the corresponding driver config settings have not been enabled.  As
Jonas Gorski suggested, we may as well apply the same check to general
platform data too.

This requires moving the code that sets the big-endian quirk flags
from the ehci_platform_reset() routine into ehci_platform_probe(), and
moving the checks out of the DT-specific "if" statement clause.

The patch also changes the text of the error messages in an attempt to
make the nature of the error more clear.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Jonas Gorski <jogo@openwrt.org>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The initial versions of the devicetree enablement patches for ehci-platform
used "ehci-platform" as compatible string. However this was disliked by various
reviewers because the platform bus is a Linux invention and devicetree is
supposed to be OS agnostic. After much discussion I gave up, added a:
"depends on !PPC_OF" to Kconfig to avoid a known conflict with PPC-OF platforms
and went with the generic usb-ehci as requested.

In retro-spect I should have chosen something different, the dts files for many
existing boards already claim to be compatible with "usb-ehci", ie they have:

	compatible = "ti,ehci-omap", "usb-ehci";

In theory this should not be a problem since the "ti,ehci-omap" entry takes
presedence, but in practice using a conflicting compatible string is an issue,
because it makes which driver gets used depend on driver registration order.

This patch changes the compatible string claimed by ehci-platform to
"generic-ehci", avoiding the driver registration / module loading ordering
problems, and removes the "depends on !PPC_OF" workaround.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Tested-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The initial versions of the devicetree enablement patches for ohci-platform
used "ohci-platform" as compatible string. However this was disliked by various
reviewers because the platform bus is a Linux invention and devicetree is
supposed to be OS agnostic. After much discussion I gave up and went with
the generic usb-ohci as requested.

In retro-spect I should have chosen something different, the dts files for many
existing boards already claim to be compatible with "usb-ohci", ie they have:

	compatible = "ti,ohci-omap3", "usb-ohci";

In theory this should not be a problem since the "ti,ohci-omap3" entry takes
presedence, but in practice using a conflicting compatible string is an issue,
because it makes which driver gets used depend on driver registration order.

This patch changes the compatible string claimed by ohci-platform to
"generic-ohci", avoiding the driver registration / module loading ordering
problems.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Tested-by: Kevin Hilman <khilman@linaro.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Allow the scheduler to select the best CPU to handle hub initalization
and LED blinking work. This extends idle residency times on idle CPUs
and conserves power.

This functionality is enabled when CONFIG_WQ_POWER_EFFICIENT is selected.

[zoran.markovic@linaro.org: Rebased to latest kernel. Added commit message.
Changed reference from system to power efficient workqueue for LEDs in
check_highspeed() and hub_port_connect_change().]
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: Xenia Ragiadakou <burzalodowa@gmail.com>
Cc: Julius Werner <jwerner@chromium.org>
Cc: Krzysztof Mazur <krzysiek@podlesie.net>
Cc: Matthias Beyer <mail@beyermatthias.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Mathias Nyman <mathias.nyman@linux.intel.com>
Cc: Thomas Pugliese <thomas.pugliese@gmail.com>
Signed-off-by: Shaibal Dutta <shaibal.dutta@broadcom.com>
Signed-off-by: Zoran Markovic <zoran.markovic@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Free "motog" on error.  This is more to appease the static checkers than
a real worry.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

According to the spec for the DWC2 controller, when the PRTINT interrupt fires,
the application must clear the appropriate status bit in the Host Port Control
and Status register to clear this bit.

When disconnecting an A-cable when the dwc2 host driver, the PRTINT fires, but
only the GINTSTS_PRTINT status is cleared, no action is done with the HPRT0
register. The HPRT0_ENACHG bit in the HPRT0 must also be poked to correctly
clear the GINTSTS_PRTINT interrupt.

I am seeing this behavoir on v2.93 of the DWC2 IP. When I disconnect an OTG
A-cable adapter, the PRTINT interrupt fires when the DWC2 is in device mode
and is never cleared.

This patch adds the function to read the HPRT0 register when the PRTINT fires
and the dwc2 IP has already transitioned to device mode. This function is only
clearing the HPRT0_ENACHG bit for now, but can be modified to handle more.
Signed-off-by: Dinh Nguyen <dinguyen@altera.com>
[ paulz: modified patch to preserve HPRT0_ENA bit ]
Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This uses the already documented devicetree booleans for this, see:
Documentation/devicetree/bindings/usb/usb-ehci.txt
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Note this commit uses the same devicetree booleans for this as the ones
already existing in the usb-ehci bindings, see:
Documentation/devicetree/bindings/usb/usb-ehci.txt
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Currently ehci-platform is only used in combination with devicetree when used
with some Via socs. By extending it to (optionally) get clks and a phy from
devicetree, and enabling / disabling those on power_on / off, it can be used
more generically. Specifically after this commit it can be used for the
ehci controller on Allwinner sunxi SoCs.

Since ehci-platform is intended to handle any generic enough non pci ehci
device, add a "usb-ehci" compatibility string.

There already is a usb-ehci device-tree bindings document, update this
with clks and phy bindings info.

Although actually quite generic so far the via,vt8500 compatibilty string
had its own bindings document. Somehow we even ended up with 2 of them. Since
these provide no extra information over the generic usb-ehci documentation,
this patch removes them.

The ehci-ppc-of.c driver also claims the usb-ehci compatibility string,
even though it mostly is ibm,usb-ehci-440epx specific. ehci-platform.c is
not needed on ppc platforms, so add a !PPC_OF dependency to it to avoid
2 drivers claiming the same compatibility string getting build on ppc.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Add support for ohci-platform instantiation from devicetree, including
optionally getting clks and a phy from devicetree, and enabling / disabling
those on power_on / off.

This should allow using ohci-platform from devicetree in various cases.
Specifically after this commit it can be used for the ohci controller found
on Allwinner sunxi SoCs.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This modifies the probing order so that any matching
dynamic entry always will be used, even if the driver
has a matching static entry.

It is sometimes useful to dynamically update existing
device entries. With the new ability to set the dynamic
entry driver_info field, this can be used to test new
additions to class driver exception lists or proposed
changes to existing static per-device driver_info
entries.
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

People sometimes create their own custom-configured kernels and forget
to enable CONFIG_SCSI_MULTI_LUN.  This causes problems when they plug
in a USB storage device (such as a card reader) with more than one
LUN.

Fortunately, we can tell fairly easily when a storage device claims to
have more than one LUN.  When that happens, this patch asks the SCSI
layer to probe all the LUNs automatically, regardless of the config
setting.

The patch also updates the Kconfig help text for usb-storage,
explaining that CONFIG_SCSI_MULTI_LUN may be necessary.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Thomas Raschbacher <lordvan@lordvan.com>
CC: Matthew Dharm <mdharm-usb@one-eyed-alien.net>
CC: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Add support for ANT USB-m Stick from Dynastream Innovations, by listing
USB pid

[34366.944805] usb 6-1: New USB device found, idVendor=0fcf, idProduct=1009
[34366.944817] usb 6-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[34366.944824] usb 6-1: Product: ANT USB-m Stick
[34366.944831] usb 6-1: Manufacturer: Dynastream Innovations

Device reported (https://code.google.com/p/antpm/issues/detail?id=5) to
work through:
$ modprobe usbserial vendor=0x0fcf product=0x1009
Signed-off-by: Kristóf Ralovich <kristof.ralovich@gmail.com>
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This patch adds an unusual-devs entry for the BlackBerry 9000.  This
fixes Bugzilla #22442.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Moritz Moeller-Herrmann <moritz-kernel@moeller-herrmann.de>
Tested-by: Moritz Moeller-Herrmann <moritz-kernel@moeller-herrmann.de>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The Cypress ATACB unusual-devs entry for the Super Top SATA bridge
causes problems.  Although it was originally reported only for
bcdDevice = 0x160, its range was much larger.  This resulted in a bug
report for bcdDevice 0x220, so the range was capped at 0x219.  Now
Milan reports errors with bcdDevice 0x150.

Therefore this patch restricts the range to just 0x160.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-and-tested-by: Milan Svoboda <milan.svoboda@centrum.cz>
CC: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

the PHY layer is supposed to be optional,
considering some PHY have no control bus
for SW to poke around.

After commit 1ae5799e (usb: hcd: Initialize
USB phy if needed) any HCD which didn't provide
a PHY driver would emit annoying error messages.

In this patch we're decreasing those messages
to debugging only and we also add a PHY prefix
or use dev_dbg so we know where they're coming from.
Reported-by: Josh Boyer <jwboyer@fedoraproject.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Josh Boyer <jwboyer@fedoraproject.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Cc: stable <stable@vger.kernel.org>
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The move from the staging tree to the main tree exposed a
longstanding memory corruption bug in the dwc2 driver. The
reordering of the driver initialization caused the dwc2 driver
to corrupt the initialization data of the sdhci driver on the
Raspberry Pi platform, which made the bug show up.

The error is in calling to_usb_device(hsotg->dev), since ->dev
is not a member of struct usb_device. The easiest fix is to
just remove the offending code, since it is not really needed.

Thanks to Stephen Warren for tracking down the cause of this.
Reported-by: Andre Heider <a.heider@gmail.com>
Tested-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Commit beb7e592 "staging: dwc2: add check on dwc2_core_reset
return" broke the B -> A role switching on OTG-enabled platforms.
This commit fixes it.
Reported-by: Dinh Nguyen <dinguyen@altera.com>
Tested-by: Dinh Nguyen <dinguyen@altera.com>
Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Add usb_disabled() check to prevent kernel oops when booting with "nousb"
in the cmdline:

Unable to handle kernel NULL pointer dereference at virtual address 00000030
...
PC is at bus_add_device+0xe0/0x18c
LR is at device_add_groups+0x1c/0x20
...
[<c02191c0>] (bus_add_device) from [<c0217130>] (device_add+0x41c/0x538)
[<c0217130>] (device_add) from [<c023b1d4>] (usb_new_device+0x270/0x35c)
[<c023b1d4>] (usb_new_device) from [<c0241174>] (usb_add_hcd+0x4fc/0x760)
[<c0241174>] (usb_add_hcd) from [<c0254ce0>] (dwc2_hcd_init+0x434/0x510)
[<c0254ce0>] (dwc2_hcd_init) from [<c02594f4>] (dwc2_driver_probe+0x130/0x170)
[<c02594f4>] (dwc2_driver_probe) from [<c021bbd0>] (platform_drv_probe+0x28/0x58)
Signed-off-by: Andre Heider <a.heider@gmail.com>
Acked-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Merge tag 'for-usb-linus-2014-02-04' of git://git.kernel.org/pub/scm/linux/kernel/git/sarah/xhci into usb-linus

Sarah writes:

xhci: Fix some regressions introduced in 3.14.

Hi Greg,

Here's four patches for 3.14.

One of them adds an xHCI host quirk, and the other three of them fix
regressions introduced in 3.14.  One regression causes USB 3.0 Link PM to
be enabled on all xHCI hosts (even those that may not support it), which
causes some USB 3.0 devices to not enumerate.  A second regression causes
some xHCI hosts that don't support 64-bit addressing to stop responding to
commands and die.

Note, these patches don't fix the recent usbfs regression that was caused
by commit 35773dac "usb: xhci: Link TRB
must not occur within a USB payload burst".  I'm waiting for those patches
to be tested.

Please pull usb-linus into usb-next, as I have feature patches that rely on
140e3026 Revert "usbcore: set lpm_capable field for LPM capable root
hubs"

Sarah Sharp

Pull parisc updates from Helge Deller:
 "The three major changes in this patchset is a implementation for
  flexible userspace memory maps, cache-flushing fixes (again), and a
  long-discussed ABI change to make EWOULDBLOCK the same value as
  EAGAIN.

  parisc has been the only platform where we had EWOULDBLOCK != EAGAIN
  to keep HP-UX compatibility.  Since we will probably never implement
  full HP-UX support, we prefer to drop this compatibility to make it
  easier for us with Linux userspace programs which mostly never checked
  for both values.  We don't expect major fall-outs because of this
  change, and if we face some, we will simply rebuild the necessary
  applications in the debian archives"

* 'parisc-3.14' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux:
  parisc: add flexible mmap memory layout support
  parisc: Make EWOULDBLOCK be equal to EAGAIN on parisc
  parisc: convert uapi/asm/stat.h to use native types only
  parisc: wire up sched_setattr and sched_getattr
  parisc: fix cache-flushing
  parisc/sti_console: prefer Linux fonts over built-in ROM fonts

HPFS needs to load 4 consecutive 512-byte sectors when accessing the
directory nodes or bitmaps.  We can't switch to 2048-byte block size
because files are allocated in the units of 512-byte sectors.

Previously, the driver would allocate a 2048-byte area using kmalloc,
copy the data from four buffers to this area and eventually copy them
back if they were modified.

In the current implementation of the buffer cache, buffers are allocated
in the pagecache.  That means that 4 consecutive 512-byte buffers are
stored in consecutive areas in the kernel address space.  So, we don't
need to allocate extra memory and copy the content of the buffers there.

This patch optimizes the code to avoid copying the buffers.  It checks
if the four buffers are stored in contiguous memory - if they are not,
it falls back to allocating a 2048-byte area and copying data there.
Signed-off-by: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>