After attempting to quickly retrieve known errors the kernel proceeds to
kick off a long running ARS. Add a module option to disable this
behavior at initialization time, or at new region discovery time.
Otherwise, ARS can be started manually regardless of the state of this
setting.
Co-developed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

ARS is an operation that can take 10s to 100s of seconds to find media
errors that should rarely be present. If the platform crashes due to
media errors in persistent memory, the expectation is that the BIOS will
report those known errors in a 'short' ARS request.

A 'short' ARS request asks platform firmware to return an ARS payload
with all known errors, but without issuing a 'long' scrub. At driver
init a short request is issued to all PMEM ranges before registering
regions. Then, in the background, a long ARS is scheduled for each
region.

The ARS implementation is simplified to centralize ARS completion work
in the ars_complete() helper. The timeout is removed since there is no
facility to cancel ARS, and this otherwise arranges for system init to
never be blocked waiting for a 'long' ARS. The ars_state flags are used
to coordinate ARS requests from driver init, ARS requests from
userspace, and ARS requests in response to media error notifications.

Given that there is no notification of ARS completion the implementation
still needs to poll. It backs off exponentially to a maximum poll period
of 30 minutes.
Suggested-by: Toshi Kani <toshi.kani@hpe.com>
Co-developed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

acpi_nfit_query_poison() is awkward in that it requires an nfit_spa
argument in order to determine what max_ars value to use. Instead probe
for the minimum max_ars across all scrub-capable ranges in the system
and drop the nfit_spa argument.

This enables a larger rework / simplification of the ARS state machine
whereby the status can be retrieved once and then iterated over all
address ranges to reap completions.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Scan the devicetree for an nvdimm-bus compatible and create
a platform device for them.
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Add device-tree binding documentation for the nvdimm region driver.

Cc: devicetree@vger.kernel.org
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

This patch adds peliminary device-tree bindings for persistent memory
regions. The driver registers a libnvdimm bus for each pmem-region
node and each address range under the node is converted to a region
within that bus.
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

We want to be able to cross reference the region and bus devices
with the device tree node that they were spawned from. libNVDIMM
handles creating the actual devices for these internally, so we
need to pass in a pointer to the relevant node in the descriptor.
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

The message about constraining number of online cpus to be less than or
equal to ND_MAX_LANES (256) is only useful for block-aperture
configurations and BTT. Make it debug since it is only relevant when
debugging performance.
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

The following NULL dereference results from incorrectly assuming that
ndd is valid in this print:

  struct nvdimm_drvdata *ndd = to_ndd(&nd_region->mapping[i]);

  /*
   * Give up if we don't find an instance of a uuid at each
   * position (from 0 to nd_region->ndr_mappings - 1), or if we
   * find a dimm with two instances of the same uuid.
   */
  dev_err(&nd_region->dev, "%s missing label for %pUb\n",
                  dev_name(ndd->dev), nd_label->uuid);

 BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
 IP: nd_region_register_namespaces+0xd67/0x13c0 [libnvdimm]
 PGD 0 P4D 0
 Oops: 0000 [#1] SMP PTI
 CPU: 43 PID: 673 Comm: kworker/u609:10 Not tainted 4.16.0-rc4+ #1
 [..]
 RIP: 0010:nd_region_register_namespaces+0xd67/0x13c0 [libnvdimm]
 [..]
 Call Trace:
  ? devres_add+0x2f/0x40
  ? devm_kmalloc+0x52/0x60
  ? nd_region_activate+0x9c/0x320 [libnvdimm]
  nd_region_probe+0x94/0x260 [libnvdimm]
  ? kernfs_add_one+0xe4/0x130
  nvdimm_bus_probe+0x63/0x100 [libnvdimm]

Switch to using the nvdimm device directly.

Fixes: 0e3b0d12 ("libnvdimm, namespace: allow multiple pmem...")
Cc: <stable@vger.kernel.org>
Reported-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

At initialization time the 'dimm' driver caches a copy of the memory
device's label area and reserves address space for each of the
namespaces defined.

However, as can be seen below, the reservation occurs even when the
index blocks are invalid:

 nvdimm nmem0: nvdimm_init_config_data: len: 131072 rc: 0
 nvdimm nmem0: config data size: 131072
 nvdimm nmem0: __nd_label_validate: nsindex0 labelsize 1 invalid
 nvdimm nmem0: __nd_label_validate: nsindex1 labelsize 1 invalid
 nvdimm nmem0: : pmem-6025e505: 0x1000000000 @ 0xf50000000 reserve <-- bad

Gate dpa reservation on the presence of valid index blocks.

Cc: <stable@vger.kernel.org>
Fixes: 4a826c83 ("libnvdimm: namespace indices: read and validate")
Reported-by: Krzysztof Rusocki <krzysztof.rusocki@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

The default value for smart ctrl_temperature was the same as the
threshold for ctrl_temperature. As a result, any arbitrary smart
injection to the nfit_test dimm could cause this alarm to trigger
and cause an acpi notification. Drop the default value to below the
threshold, so that unrelated injections don't trigger notifications.

Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Add support for the smart injection command in the nvdimm unit test
framework. This allows for directly injecting to smart fields and flags
that are supported in the injection command. If the injected values are
past the threshold, then an acpi notification is also triggered.

Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

In preparation for re-working the ARS implementation to better handle
short vs long ARS runs, introduce nfit_spa->ars_state. For now this just
replaces the nfit_spa->ars_required bit-field/flag, but going forward it
will be used to track ARS completion and make short vs long ARS
requests.
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

For debug, it is useful for bus providers to be able to retrieve the
'struct device' associated with an nd_region instance that it
registered. We already have to_nd_region() to perform the reverse cast
operation, in fact its duplicate declaration can be removed from the
private drivers/nvdimm/nd.h header.
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

There is a small window whereby ARS scan requests can schedule work that
userspace will miss when polling scrub_show. Hold the init_mutex lock
over calls to report the status to close this potential escape. Also,
make sure that requests to cancel the ARS workqueue are treated as an
idle event.

Cc: <stable@vger.kernel.org>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Fixes: 37b137ff ("nfit, libnvdimm: allow an ARS scrub...")
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Commit 1cf03c00 "nfit: scrub and register regions in a workqueue"
mistakenly attempts to register a region per BLK aperture. There is
nothing to register for individual apertures as they belong as a set to
a BLK aperture group that are registered with a corresponding
DIMM-control-region. Filter them for registration to prevent some
needless devm_kzalloc() allocations.

Cc: <stable@vger.kernel.org>
Fixes: 1cf03c00 ("nfit: scrub and register regions in a workqueue")
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Some BIOSen do not handle 0-byte transfer lengths for the _LSR and _LSW
(label storage read/write) methods. This causes Linux to fallback to the
deprecated _DSM path, or otherwise disable label support.

Introduce acpi_nvdimm_has_method() to detect whether a method is
available rather than calling the method, require _LSI and _LSR to be
paired, and require read support before enabling write support.

Cc: <stable@vger.kernel.org>
Fixes: 4b27db7e ("acpi, nfit: add support for the _LS...")
Suggested-by: Erik Schmauss <erik.schmauss@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Per the ACPI specification the only functional purpose for a DIMM
Control Region to be mapped into the system physical address space, from
an OSPM perspective, is to support block-apertures. However, there are
some BIOSen that publish DIMM Control Region SPA entries for pre-boot
environment consumption.  Undo the kernel policy of generating disabled
'ndblk' regions when this configuration is detected.

Cc: <stable@vger.kernel.org>
Fixes: 1f7df6f8 ("libnvdimm, nfit: regions (block-data-window...)")
Reviewed-by: Toshi Kani <toshi.kani@hpe.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

sizeof_namespace_index() fails when NVDIMM devices have the minimum
1024 bytes label storage area.  nvdimm_num_label_slots() returns 3
slots while the area is only big enough for 2 slots.

Change nvdimm_num_label_slots() to calculate a number of label slots
according to UEFI 2.7 spec.
Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

UEFI 2.7 defines in page 758 that:

  Initial Label Storage Area Configuration
     :
  The minimum size of the Label Storage Area is large enough to
  hold 2 index blocks and 2 labels.

The mininum index block size is 256 bytes, and the minimum label size
is also 256 bytes.

Change ND_LABEL_MIN_SIZE to (256 * 4) so that NVDIMM devices with
the minimum label storage area do not fail with the size check in
nvdimm_init_config_data().
Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Use module_nd_driver() instead of having module_init() and
module_exit() callbacks which just call nd_driver_register() and
nd_driver_unregister().
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Use module_nd_driver() instead of having module_init() and
module_exit() callbacks which just call nd_driver_register() and
nd_driver_unregister().
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Provide a module_nd_driver() wrapper over simple nd_driver_register()
nd_driver_unregister() combinations in module_init() and module_exit()
respectively.

Note an explicit nd_driver_unregister() had to be implemented as nd
bus drivers did call device_unregister() direcly in the module_exit()
function.
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

When you load nfit_test you currently see the following error in dmesg:

 nfit_test nfit_test.0: found a zero length table '0' parsing nfit

This happens because when we parse the nfit_test.0 table via
acpi_nfit_init(), we specify a size of nfit_test->nfit_size.  For the first
pass through nfit_test.0 where (t->setup_hotplug == 0) this is the size of
the entire buffer we allocated, including space for the hot plug
structures, not the size that we've actually filled in.

Fix this by only trying to parse the size of the structures that we've
filled in.
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

It turns out that we were overrunning the 'nfit_buf' buffer in
nfit_test0_setup() in the (t->setup_hotplug == 1) case because we failed to
correctly account for all of the acpi_nfit_memory_map structures.

Fix the structure count which will increase the allocation size of
'nfit_buf' in nfit_test0_alloc().  Also add some WARN_ON()s to
nfit_test0_setup() and nfit_test1_setup() to catch future issues where the
size of the buffer doesn't match the amount of data we're writing.
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

In nfit_test0_setup() and nfit_test1_setup() we keep an 'offset' value
which we use to calculate where in our 'nfit_buf' we will place our next
structure.  The handling of 'offset' and the calculation of the placement
of the next structure is a bit inconsistent, though.  We don't update
'offset' after we insert each structure, sometimes causing us to update it
for multiple structures' sizes at once.  When calculating the position of
the next structure we aren't always able to just use 'offset', but
sometimes have to add in other structure sizes as well.

Fix this by updating 'offset' after each structure insertion in a
consistent way, allowing us to always calculate the position of the next
structure to be inserted by just using 'nfit_buf + offset'.
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Dynamic debug can be instructed to add the function name to the debug
output using the +f switch, so there is no need for the dax modules to
do it again. If a user decides to add the +f switch for the dax modules'
dynamic debug this results in double prints of the function name.
Reported-by: Johannes Thumshirn <jthumshirn@suse.de>
Reported-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Dynamic debug can be instructed to add the function name to the debug
output using the +f switch, so there is no need for the libnvdimm
modules to do it again. If a user decides to add the +f switch for
libnvdimm's dynamic debug this results in double prints of the function
name.
Reported-by: Johannes Thumshirn <jthumshirn@suse.de>
Reported-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Dynamic debug can be instructed to add the function name to the debug
output using the +f switch, so there is no need for the nfit module to
do it again. If a user decides to add the +f switch for nfit's dynamic
debug this results in double prints of the function name like the
following:

[ 2391.935383] acpi_nfit_ctl: nfit ACPI0012:00: acpi_nfit_ctl:nmem8 cmd: 10: func: 1 input length: 0

Thus remove the stray __func__ printing.
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Pull x86 fixes from Thomas Gleixner:
 "A small set of fixes for x86:

   - Add missing instruction suffixes to assembly code so it can be
     compiled by newer GAS versions without warnings.

   - Switch refcount WARN exceptions to UD2 as we did in general

   - Make the reboot on Intel Edison platforms work

   - A small documentation update so text and sample command match"

* 'x86/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  Documentation, x86, resctrl: Make text and sample command match
  x86/platform/intel-mid: Handle Intel Edison reboot correctly
  x86/asm: Add instruction suffixes to bitops
  x86/entry/64: Add instruction suffix
  x86/refcounts: Switch to UD2 for exceptions

Pull x86/pti fixes from Thomas Gleixner:
 "Three fixes related to melted spectrum:

   - Sync the cpu_entry_area page table to initial_page_table on 32 bit.

     Otherwise suspend/resume fails because resume uses
     initial_page_table and triggers a triple fault when accessing the
     cpu entry area.

   - Zero the SPEC_CTL MRS on XEN before suspend to address a
     shortcoming in the hypervisor.

   - Fix another switch table detection issue in objtool"

* 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/cpu_entry_area: Sync cpu_entry_area to initial_page_table
  objtool: Fix another switch table detection issue
  x86/xen: Zero MSR_IA32_SPEC_CTRL before suspend

Pull timer fixes from Thomas Gleixner:
 "A small set of fixes from the timer departement:

   - Add a missing timer wheel clock forward when migrating timers off a
     unplugged CPU to prevent operating on a stale clock base and
     missing timer deadlines.

   - Use the proper shift count to extract data from a register value to
     prevent evaluating unrelated bits

   - Make the error return check in the FSL timer driver work correctly.
     Checking an unsigned variable for less than zero does not really
     work well.

   - Clarify the confusing comments in the ARC timer code"

* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  timers: Forward timer base before migrating timers
  clocksource/drivers/arc_timer: Update some comments
  clocksource/drivers/mips-gic-timer: Use correct shift count to extract data
  clocksource/drivers/fsl_ftm_timer: Fix error return checking

Pull irq fixlet from Thomas Gleixner:
 "Just a documentation update for the missing device tree property of
  the R-Car M3N interrupt controller"

* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  dt-bindings/irqchip/renesas-irqc: Document R-Car M3-N support

Pull btrfs fixes from David Sterba:

 - when NR_CPUS is large, a SRCU structure can significantly inflate
   size of the main filesystem structure that would not be possible to
   allocate by kmalloc, so the kvalloc fallback is used

 - improved error handling

 - fix endiannes when printing some filesystem attributes via sysfs,
   this is could happen when a filesystem is moved between different
   endianity hosts

 - send fixes: the NO_HOLE mode should not send a write operation for a
   file hole

 - fix log replay for for special files followed by file hardlinks

 - fix log replay failure after unlink and link combination

 - fix max chunk size calculation for DUP allocation

* tag 'for-4.16-rc3-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  Btrfs: fix log replay failure after unlink and link combination
  Btrfs: fix log replay failure after linking special file and fsync
  Btrfs: send, fix issuing write op when processing hole in no data mode
  btrfs: use proper endianness accessors for super_copy
  btrfs: alloc_chunk: fix DUP stripe size handling
  btrfs: Handle btrfs_set_extent_delalloc failure in relocate_file_extent_cluster
  btrfs: handle failure of add_pending_csums
  btrfs: use kvzalloc to allocate btrfs_fs_info

Pull i2c fixes from Wolfram Sang:
 "A driver fix and a documentation fix (which makes dependency handling
  for the next cycle easier)"

* 'i2c/for-current-fixed' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux:
  i2c: octeon: Prevent error message on bus error
  dt-bindings: at24: sort manufacturers alphabetically

Pull libnvdimm fixes from Dan Williams:
 "A 4.16 regression fix, three fixes for -stable, and a cleanup fix:

   - During the merge window support for the new ACPI NVDIMM Platform
     Capabilities structure disabled support for "deep flush", a
     force-unit- access like mechanism for persistent memory. Restore
     that mechanism.

   - VFIO like RDMA is yet one more memory registration / pinning
     interface that is incompatible with Filesystem-DAX. Disable long
     term pins of Filesystem-DAX mappings via VFIO.

   - The Filesystem-DAX detection to prevent long terms pins mistakenly
     also disabled Device-DAX pins which are not subject to the same
     block- map collision concerns.

   - Similar to the setup path, softlockup warnings can trigger in the
     shutdown path for large persistent memory namespaces. Teach
     for_each_device_pfn() to perform cond_resched() in all cases.

   - Boaz noticed that the might_sleep() in dax_direct_access() is stale
     as of the v4.15 kernel.

  These have received a build success notification from the 0day robot,
  and the longterm pin fixes have appeared in -next. However, I recently
  rebased the tree to remove some other fixes that need to be reworked
  after review feedback.

* 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  memremap: fix softlockup reports at teardown
  libnvdimm: re-enable deep flush for pmem devices via fsync()
  vfio: disable filesystem-dax page pinning
  dax: fix vma_is_fsdax() helper
  dax: ->direct_access does not sleep anymore

Merge tag 'kbuild-fixes-v4.16' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild

Pull Kbuild fixes from Masahiro Yamada:

 - suppress sparse warnings about unknown attributes

 - fix typos and stale comments

 - fix build error of arch/sh

 - fix wrong use of ld-option vs cc-ldoption

 - remove redundant GCC_PLUGINS_CFLAGS assignment

 - fix another memory leak of Kconfig

 - fix line number in error messages of Kconfig

 - do not write confusing CONFIG_DEFCONFIG_LIST out to .config

 - add xstrdup() to Kconfig to handle memory shortage errors

 - show also a Debian package name if ncurses is missing

* tag 'kbuild-fixes-v4.16' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  MAINTAINERS: take over Kconfig maintainership
  kconfig: fix line number in recursive inclusion error message
  Coccinelle: memdup: Fix typo in warning messages
  kconfig: Update ncurses package names for menuconfig
  kbuild/kallsyms: trivial typo fix
  kbuild: test --build-id linker flag by ld-option instead of cc-ldoption
  kbuild: drop superfluous GCC_PLUGINS_CFLAGS assignment
  kconfig: Don't leak choice names during parsing
  sh: fix build error for empty CONFIG_BUILTIN_DTB_SOURCE
  kconfig: set SYMBOL_AUTO to the symbol marked with defconfig_list
  kconfig: add xstrdup() helper
  kbuild: disable sparse warnings about unknown attributes
  Makefile: Fix lying comment re. silentoldconfig

Pull media fixes from Mauro Carvalho Chehab:

  - some build fixes with randconfigs

  - an m88ds3103 fix to prevent an OOPS if the chip doesn't provide the
    right version during probe (with can happen if the hardware hangs)

  - a potential out of array bounds reference in tvp5150

  - some fixes and improvements in the DVB memory mapped API (added for
    kernel 4.16)

* tag 'media/v4.16-3' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media:
  media: vb2: Makefile: place vb2-trace together with vb2-core
  media: Don't let tvp5150_get_vbi() go out of vbi_ram_default array
  media: dvb: update buffer mmaped flags and frame counter
  media: dvb: add continuity error indicators for memory mapped buffers
  media: dmxdev: Fix the logic that enables DMA mmap support
  media: dmxdev: fix error code for invalid ioctls
  media: m88ds3103: don't call a non-initalized function
  media: au0828: add VIDEO_V4L2 dependency
  media: dvb: fix DVB_MMAP dependency
  media: dvb: fix DVB_MMAP symbol name
  media: videobuf2: fix build issues with vb2-trace
  media: videobuf2: Add VIDEOBUF2_V4L2 Kconfig option for VB2 V4L2 part

Pull watchdog fixes from Wim Van Sebroeck:

 - rave-sp: add NVMEM dependency

 - build fixes for i6300esb_wdt, xen_wdt and sp5100_tco

* tag 'linux-watchdog-4.16-fixes-1' of git://www.linux-watchdog.org/linux-watchdog:
  watchdog: sp5100_tco.c: fix potential build failure
  watchdog: xen_wdt: fix potential build failure
  watchdog: i6300esb: fix build failure
  watchdog: rave-sp: add NVMEM dependency