Reported by Mikulas Patocka, kmemcheck currently barks out a
false positive since we don't have special kmemcheck annotation
for bitfields used in bpf_prog structure.

We currently have jited:1, len:31 and thus when accessing len
while CONFIG_KMEMCHECK enabled, kmemcheck throws a warning that
we're reading uninitialized memory.

As we don't need the whole bit universe for pages member, we
can just split it to u16 and use a bool flag for jited instead
of a bitfield.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This is the ARM variant for 314beb9b ("x86: bpf_jit_comp: secure bpf
jit against spraying attacks").

It is now possible to implement it due to commits 75374ad4 ("ARM: mm:
Define set_memory_* functions for ARM") and dca9aa92 ("ARM: add
DEBUG_SET_MODULE_RONX option to Kconfig") which added infrastructure for
this facility.

Thus, this patch makes sure the BPF generated JIT code is marked RO, as
other kernel text sections, and also lets the generated JIT code start
at a pseudo random offset instead on a page boundary. The holes are filled
with illegal instructions.

JIT tested on armv7hl with BPF test suite.

Reference: http://mainisusuallyafunction.blogspot.com/2012/11/attacking-hardened-linux-systems-with.htmlSigned-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Mircea Gherzan <mgherzan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Introduced in commit 314beb9b ("x86: bpf_jit_comp: secure bpf jit
against spraying attacks") and later on replicated in aa2d2c73
("s390/bpf,jit: address randomize and write protect jit code") for
s390 architecture, write protection for BPF JIT images got added and
a random start address of the JIT code, so that it's not on a page
boundary anymore.

Since both use a very similar allocator for the BPF binary header,
we can consolidate this code into the BPF core as it's mostly JIT
independant anyway.

This will also allow for future archs that support DEBUG_SET_MODULE_RONX
to just reuse instead of reimplementing it.

JIT tested on x86_64 and s390x with BPF test suite.
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Alexander Duyck reported high false sharing on dst refcount in tcp stack
when prequeue is used. prequeue is the mechanism used when a thread is
blocked in recvmsg()/read() on a TCP socket, using a blocking model
rather than select()/poll()/epoll() non blocking one.

We already try to use RCU in input path as much as possible, but we were
forced to take a refcount on the dst when skb escaped RCU protected
region. When/if the user thread runs on different cpu, dst_release()
will then touch dst refcount again.

Commit 09316255 (tcp: force a dst refcount when prequeue packet)
was an example of a race fix.

It turns out the only remaining usage of skb->dst for a packet stored
in a TCP socket prequeue is IP early demux.

We can add a logic to detect when IP early demux is probably going
to use skb->dst. Because we do an optimistic check rather than duplicate
existing logic, we need to guard inet_sk_rx_dst_set() and
inet6_sk_rx_dst_set() from using a NULL dst.

Many thanks to Alexander for providing a nice bug report, git bisection,
and reproducer.

Tested using Alexander script on a 40Gb NIC, 8 RX queues.
Hosts have 24 cores, 48 hyper threads.

echo 0 >/proc/sys/net/ipv4/tcp_autocorking

for i in `seq 0 47`
do
  for j in `seq 0 2`
  do
     netperf -H $DEST -t TCP_STREAM -l 1000 \
             -c -C -T $i,$i -P 0 -- \
             -m 64 -s 64K -D &
  done
done

Before patch : ~6Mpps and ~95% cpu usage on receiver
After patch : ~9Mpps and ~35% cpu usage on receiver.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

After merging the wireless-next tree, today's linux-next build (powerpc
allyesconfig) failed like this:

drivers/net/wireless/ath/ath5k/debug.c: In function 'open_file_eeprom':
drivers/net/wireless/ath/ath5k/debug.c:933:2: error: implicit declaration of function 'vmalloc' [-Werror=implicit-function-declaration]
  buf = vmalloc(eesize);
  ^
drivers/net/wireless/ath/ath5k/debug.c:933:6: warning: assignment makes pointer from integer without a cast
  buf = vmalloc(eesize);
      ^
drivers/net/wireless/ath/ath5k/debug.c:960:2: error: implicit declaration of function 'vfree' [-Werror=implicit-function-declaration]
  vfree(buf);
  ^

Caused by commit db906eb2 ("ath5k: added debugfs file for dumping
eeprom").  Also reported by Guenter Roeck.

I have used Geert Uytterhoeven's suggested fix of including vmalloc.h
and so added this patch for today:

From: Stephen Rothwell <sfr@canb.auug.org.au>
Date: Mon, 8 Sep 2014 18:39:23 +1000
Subject: [PATCH] ath5k: fix debugfs addition
Reported-by: Guenter Roeck <linux@roeck-us.net>
Suggested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

It removes the owner field updation of driver structure.
It will be automatically updated by module_platform_driver()
Signed-off-by: Varka Bhadram <varkab@cdac.in>
Signed-off-by: David S. Miller <davem@davemloft.net>

Change the date type of error status from u64 to atomic_long_t, and use atomic
operation, then remove the lock which is used to protect the error status.

The operation of atomic maybe faster than spin lock.

Cc: Pravin Shelar <pshelar@nicira.com>
Signed-off-by: Li RongQing <roy.qing.li@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This patch removes an unncessary check in the br_afspec() method of
br_netlink.c.
Signed-off-by: Rami Rosen <ramirose@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Jiri Pirko says:

====================
bridge: implement rtnl_link options for getting and setting bridge options

So far, only sysfs is complete interface for getting and setting bridge
options. This patchset follows-up on the similar bonding code and
allows userspace to get/set bridge master/port options using Netlink
IFLA_INFO_DATA/IFLA_INFO_SLAVE_DATA attr.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

Allow rtnetlink users to set bridge master info via IFLA_INFO_DATA attr
This initial part implements forward_delay, hello_time, max_age options.
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>

Allow rtnetlink users to get bridge master info in IFLA_INFO_DATA attr
This initial part implements forward_delay, hello_time, max_age options.
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>

Allow rtnetlink users to set port info via IFLA_INFO_SLAVE_DATA attr
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>

Allow rtnetlink users to get port info in IFLA_INFO_SLAVE_DATA attr
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>

The thing is that netdev_master_upper_dev_link calls
call_netdevice_notifiers(NETDEV_CHANGEUPPER, dev). That generates rtnl
link message and during that, rtnl_link_ops->fill_slave_info is called.
But with current ordering, rx_handler and IFF_BRIDGE_PORT are not set
yet so there would have to be check for that in fill_slave_info callback.

Resolve this by reordering to similar what bonding and team does to
avoid the check.

Also add removal of IFF_BRIDGE_PORT flag into error path.
Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>

net.ipv4.ip_nonlocal_bind sysctl was global to all network
namespaces. This patch allows to set a different value for each
network namespace.
Signed-off-by: Vincent Bernat <vincent@bernat.im>
Signed-off-by: David S. Miller <davem@davemloft.net>

Alexei Starovoitov says:

====================
load imm64 insn and uapi/linux/bpf.h

V9->V10
- no changes, added Daniel's ack

Note they're on top of Hannes's patch in the same area [1]

V8 thread with 'why' reasoning and end goal [2]

Original set [3] of ~28 patches I'm planning to present in 4 stages:

  I. this 2 patches to fork off llvm upstreaming
 II. bpf syscall with manpage and map implementation
III. bpf program load/unload with verifier testsuite (1st user of
     instruction macros from bpf.h and 1st user of load imm64 insn)
 IV. tracing, etc

[1] http://patchwork.ozlabs.org/patch/385266/
[2] https://lkml.org/lkml/2014/8/27/628
[3] https://lkml.org/lkml/2014/8/26/859
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

allow user space to generate eBPF programs

uapi/linux/bpf.h: eBPF instruction set definition

linux/filter.h: the rest

This patch only moves macro definitions, but practically it freezes existing
eBPF instruction set, though new instructions can still be added in the future.

These eBPF definitions cannot go into uapi/linux/filter.h, since the names
may conflict with existing applications.

Full eBPF ISA description is in Documentation/networking/filter.txt
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

add BPF_LD_IMM64 instruction to load 64-bit immediate value into a register.
All previous instructions were 8-byte. This is first 16-byte instruction.
Two consecutive 'struct bpf_insn' blocks are interpreted as single instruction:
insn[0].code = BPF_LD | BPF_DW | BPF_IMM
insn[0].dst_reg = destination register
insn[0].imm = lower 32-bit
insn[1].code = 0
insn[1].imm = upper 32-bit
All unused fields must be zero.

Classic BPF has similar instruction: BPF_LD | BPF_W | BPF_IMM
which loads 32-bit immediate value into a register.

x64 JITs it as single 'movabsq %rax, imm64'
arm64 may JIT as sequence of four 'movk x0, #imm16, lsl #shift' insn

Note that old eBPF programs are binary compatible with new interpreter.

It helps eBPF programs load 64-bit constant into a register with one
instruction instead of using two registers and 4 instructions:
BPF_MOV32_IMM(R1, imm32)
BPF_ALU64_IMM(BPF_LSH, R1, 32)
BPF_MOV32_IMM(R2, imm32)
BPF_ALU64_REG(BPF_OR, R1, R2)

User space generated programs will use this instruction to load constants only.

To tell kernel that user space needs a pointer the _pseudo_ variant of
this instruction may be added later, which will use extra bits of encoding
to indicate what type of pointer user space is asking kernel to provide.
For example 'off' or 'src_reg' fields can be used for such purpose.
src_reg = 1 could mean that user space is asking kernel to validate and
load in-kernel map pointer.
src_reg = 2 could mean that user space needs readonly data section pointer
src_reg = 3 could mean that user space needs a pointer to per-cpu local data
All such future pseudo instructions will not be carrying the actual pointer
as part of the instruction, but rather will be treated as a request to kernel
to provide one. The kernel will verify the request_for_a_pointer, then
will drop _pseudo_ marking and will store actual internal pointer inside
the instruction, so the end result is the interpreter and JITs never
see pseudo BPF_LD_IMM64 insns and only operate on generic BPF_LD_IMM64 that
loads 64-bit immediate into a register. User space never operates on direct
pointers and verifier can easily recognize request_for_pointer vs other
instructions.
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Merge tag 'master-2014-09-08' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-next

John W. Linville says:

====================
pull request: wireless-next 2014-09-08

Please pull this batch of updates intended for the 3.18 stream...

For the mac80211 bits, Johannes says:

"Not that much content this time. Some RCU cleanups, crypto
performance improvements, and various patches all over,
rather than listing them one might as well look into the
git log instead."

For the Bluetooth bits, Gustavo says:

"The changes consists of:

        - Coding style fixes to HCI drivers
        - Corrupted ack value fix for the H5 HCI driver
        - A couple of Enhanced L2CAP fixes
        - Conversion of SMP code to use common L2CAP channel API
        - Page scan optimizations when using the kernel-side whitelist
        - Various mac802154 and and ieee802154 6lowpan cleanups
        - One new Atheros USB ID"

For the iwlwifi bits, Emmanuel says:

"We have a new big thing coming up which is called Dynamic Queue
Allocation (or DQA).  This is a completely new way to work with the
Tx queues and it requires major refactoring.  This is being done by
Johannes and Avri.  Besides this, Johannes disables U-APSD by default
because of APs that would disable A-MPDU if the association supports
U-ASPD.  Luca contributed to the power area which he was cleaning
up on the way while working on CSA.  A few more random things here
and there."

For the Atheros bits, Kalle says:

"For ath6kl we had two small fixes and a new SDIO device id.

For ath10k the bigger changes are:

 * support for new firmware version 10.2 (Michal)

 * spectral scan support (Simon, Sven & Mathias)

 * export a firmware crash dump file (Ben & me)

 * cleaning up of pci.c (Michal)

 * print pci id in all messages, which causes most of the churn (Michal)"

Beyond that, we have the usual collection of various updates to ath9k,
b43, mwifiex, and wil6210, as well as a few other bits here and there.

Please let me know if there are problems!
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

inetpeer sequence numbers are no longer incremented, so no need to
check and flush the tree. The function that increments the sequence
number was already dead code and removed in in "ipv4: remove unused
function" (068a6e18). Remove the code that checks for a change, too.

Verifying that v4_seq and v6_seq are never incremented and thus that
flush_check compares bp->flush_seq to 0 is trivial.

The second part of the change removes flush_check completely even
though bp->flush_seq is exactly !0 once, at initialization. This
change is correct because the time this branch is true is when
bp->root == peer_avl_empty_rcu, in which the branch and
inetpeer_invalidate_tree are a NOOP.
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

CPSW supports both rx and tx pause frames for flow control.
Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

A bit of floor sweeping in a dusty old corner.  Convert the "normal"
skb free calls to dev_consume_skb_any() so packet drop tracing will
be more sane.
Signed-off-by: Rick Jones <rick.jones2@hp.com>
Acked-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: David S. Miller <davem@davemloft.net>

GRE assumes that the GRE header is at skb_network_header +
ip_hrdlen(skb). It is more general to use skb_transport_header
and this allows the possbility of inserting additional header
between IP and GRE (which is what we will done in Generic UDP
Encapsulation for GRE).
Signed-off-by: Tom Herbert <therbert@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This change makes it so that dp83640_remove can use skb_queue_purge
instead of looping through itself to flush any entries out of the queue.
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Pull cgroup fixes from Tejun Heo:
 "This pull request includes Alban's patch to disallow '\n' in cgroup
  names.

  Two other patches from Li to fix a possible oops when cgroup
  destruction races against other file operations and one from Vivek to
  fix a unified hierarchy devel behavior"

* 'for-3.17-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: check cgroup liveliness before unbreaking kernfs
  cgroup: delay the clearing of cgrp->kn->priv
  cgroup: Display legacy cgroup files on default hierarchy
  cgroup: reject cgroup names with '\n'

Pull percpu fixes from Tejun Heo:
 "One patch to fix a failure path in the alloc path.  The bug is
  dangerous but probably not too likely to actually trigger in the wild
  given that there hasn't been any report yet.

  The other two are low impact fixes"

* 'for-3.17-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu:
  percpu: free percpu allocation info for uniprocessor system
  percpu: perform tlb flush after pcpu_map_pages() failure
  percpu: fix pcpu_alloc_pages() failure path

Pull libata fixes from Tejun Heo:
 "Two patches are to add PCI IDs for ICH9 and all others are device
  specific fixes.  Nothing too interesting"

* 'for-3.17-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/libata:
  ahci_xgene: Fix the link down in first attempt for the APM X-Gene SoC AHCI SATA host controller driver.
  ahci_xgene: Skip the PHY and clock initialization if already configured by the firmware.
  ahci: add pcid for Marvel 0x9182 controller
  ata: Disabling the async PM for JMicron chip 363/361
  ata_piix: Add Device IDs for Intel 9 Series PCH
  ahci: Add Device IDs for Intel 9 Series PCH
  ata: ahci_tegra: Read calibration fuse

Pull networking fixes from David Miller:

 1) Fix skb leak in mac802154, from Martin Townsend

 2) Use select not depends on NF_NAT for NFT_NAT, from Pablo Neira
    Ayuso

 3) Fix union initializer bogosity in vxlan, from Gerhard Stenzel

 4) Fix RX checksum configuration in stmmac driver, from Giuseppe
    CAVALLARO

 5) Fix TSO with non-accelerated VLANs in e1000, e1000e, bna, ehea,
    i40e, i40evf, mvneta, and qlge, from Vlad Yasevich

 6) Fix capability checks in phy_init_eee(), from Giuseppe CAVALLARO

 7) Try high order allocations more sanely for SKBs, specifically if a
    high order allocation fails, fall back directly to zero order pages
    rather than iterating down one order at a time.  From Eric Dumazet

 8) Fix a memory leak in openvswitch, from Li RongQing

 9) amd-xgbe initializes wrong spinlock, from Thomas Lendacky

10) RTNL locking was busted in setsockopt for anycast and multicast, fix
    from Sabrina Dubroca

11) Fix peer address refcount leak in ipv6, from Nicolas Dichtel

12) DocBook typo fixes, from Masanari Iida

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (101 commits)
  ipv6: restore the behavior of ipv6_sock_ac_drop()
  amd-xgbe: Enable interrupts for all management counters
  amd-xgbe: Treat certain counter registers as 64 bit
  greth: moved TX ring cleaning to NAPI rx poll func
  cnic : Cleanup CONFIG_IPV6 & VLAN check
  net: treewide: Fix typo found in DocBook/networking.xml
  bnx2x: Fix link problems for 1G SFP RJ45 module
  3c59x: avoid panic in boomerang_start_xmit when finding page address:
  netfilter: add explicit Kconfig for NETFILTER_XT_NAT
  ipv6: use addrconf_get_prefix_route() to remove peer addr
  ipv6: fix a refcnt leak with peer addr
  net-timestamp: only report sw timestamp if reporting bit is set
  drivers/net/fddi/skfp/h/skfbi.h: Remove useless PCI_BASE_2ND macros
  l2tp: fix race while getting PMTU on PPP pseudo-wire
  ipv6: fix rtnl locking in setsockopt for anycast and multicast
  VMXNET3: Check for map error in vmxnet3_set_mc
  openvswitch: distinguish between the dropped and consumed skb
  amd-xgbe: Fix initialization of the wrong spin lock
  openvswitch: fix a memory leak
  netfilter: fix missing dependencies in NETFILTER_XT_TARGET_LOG
  ...

The mdio-sun4i driver automatically selects REGULATOR and
REGULATOR_FIXED_VOLTAGE because it uses the regulator API. But a
driver selecting a subsystem increases the chance of generating
circular Kconfig dependencies, especially when other drivers depend on
the selected symbol.

Since the regulator API functions are replaced with no-ops when
REGULATOR is disabled, the driver can be built successfully even
without regulator support and so those 'select' dependencies can be
safely dropped.
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Beniamino Galvani <b.galvani@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

John W. Linville says:

====================
pull request: wireless 2014-09-05

Please pull this batch of fixes intended for the 3.17 stream...

For the mac80211 bits, Johannes says:

"Here are a few fixes for mac80211. One has been discussed for a while
and adds a terminating NUL-byte to the alpha2 sent to userspace, which
shouldn't be necessary but since many places treat it as a string we
couldn't move to just sending two bytes.

In addition to that, we have two VLAN fixes from Felix, a mesh fix, a
fix for the recently introduced RX aggregation offload, a revert for
a broken patch (that luckily didn't really cause any harm) and a small
fix for alignment in debugfs."

For the iwlwifi bits, Emmanuel says:

"I revert a patch that disabled CTS to self in dvm because users
reported issues. The revert is CCed to stable since the offending
patch was sent to stable too. I also bump the firmware API versions
since a new firmware is coming up. On top of that, Marcel fixes a
bug I introduced while fixing a bug in our Kconfig file."

Please let me know if there are problems!
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

It is possible that the interface is already gone after joining
the list of anycast on this interface as we don't hold a refcount
for the device, in this case we are safe to ignore the error.

What's more important, for API compatibility we should not
change this behavior for applications even if it were correct.

Fixes: commit a9ed4a29 ("ipv6: fix rtnl locking in setsockopt for anycast and multicast")
Cc: Sabrina Dubroca <sd@queasysnail.net>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Instead of dereference each byte let's use %*ph specifier in the printk()
calls.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

new link for - How to piss off a Linux kernel subsystem maintainer
Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The NFS/RDMA Kconfig symbol was split into separate options for client
and server in commit 2e8c12e1 ("xprtrdma: add separate Kconfig
options for NFSoRDMA client and server support").

Update the documentation to reflect this split.
Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: "J. Bruce Fields" <bfields@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

hpfall.c was renamed to freefall.c in 3.16, but this file still refer to
hpfall.c instead of freefall.c
Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

The example code provided with the i2c device interface documentation
won't compile since it uses the reserved word "register" to name a
variable.

The compiler fails with this error message:

 error: expected identifier or '(' before '=' token
   __u8 register = 0x20; /* Device register to access */
                 ^

Rename the variable "register" to simply "reg" in the example code.

Another couple of typos has been fixed as well.
[Change "! =" to "!=".]
Signed-off-by: Jose Alarcon Roldan <jose.alarcon.roldan@gmail.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Despite the fact that these functions have been around for years, they
are little used (only 15 uses in 13 files at the preseht time) even
though many other files use work-arounds to achieve the same result.

By documenting them, hopefully they will become more widely used.
Signed-off-by: Rob Jones <rob.jones@codethink.co.uk>
Acked-by: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>