* make ata_scsiop_*() static
* make ata_scsi_set_sense() static and move it above its users
* make ata_scsi_rbuf_fill() static
* kill unused ata_scsi_badcmd()
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
Make PMP support optional by adding CONFIG_SATA_PMP and leaving out
libata-pmp.c if it isn't set. PMP helpers return constant values if
PMP support is not enabled and PMP declarations alias non-PMP
counterparts. This makes the compiler to leave out PMP related part
out and LLDs to use non-PMP counterparts automatically.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Most of PMP support code is already in libata-pmp.c. All that are in
libata-core.c are sata_pmp_port_ops and EXPORTs. Move them to
libata-pmp.c. Also, collect PMP related prototypes and declarations
in header files and move them right above of SFF stuff.
This change is to make PMP support optional.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Now that SFF support is completely separated out from the core layer,
it can be made optional. Add CONFIG_ATA_SFF and let SFF drivers
depend on it. If CONFIG_ATA_SFF isn't set, all codes in libata-sff.c
and data structures for SFF support are disabled. This saves good
number of bytes for small systems.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Implement sata_std_hardreset(), which simply wraps around
sata_link_hardreset(). sata_std_hardreset() becomes new standard
hardreset method for sata_port_ops and sata_sff_hardreset() moves from
ata_base_port_ops to ata_sff_port_ops, which is where it really
belongs.
ata_is_builtin_hardreset() is added so that both
ata_std_error_handler() and ata_sff_error_handler() skip both builtin
hardresets if SCR isn't accessible.
piix_sidpr_hardreset() in ata_piix.c is identical to
sata_std_hardreset() in functionality and got replaced with the
standard function.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Factor out waiting logic (which is common to all ATA controllers) from
ata_sff_wait_ready() into ata_wait_ready(). ata_wait_ready() takes
@check_ready function pointer and uses it to poll for readiness. This
allows non-SFF controllers to use ata_wait_ready() to wait for link
readiness.
This patch also implements ata_wait_after_reset() - generic version of
ata_sff_wait_after_reset() - using ata_wait_ready().
ata_sff_wait_ready() is reimplemented using ata_wait_ready() and
ata_sff_check_ready(). Functionality remains the same.
Signed-off-by: Tejun Heo <htejun@gmail.com>
ata_flush_code() hasn't been in use for quite some time now. Kill it.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
ata_tf_to_lba[48]() currently return LBA in tf + 1 for
ata_read_native_max_address(). Make them return LBA and make it
global so that it can be used to read LBA off TF for other purposes.
ata_read_native_max_address() now adds 1 itself.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
* Move SFF related functions from libata-core.c to libata-sff.c.
ata_[bmdma_]sff_port_ops, ata_devchk(), ata_dev_try_classify(),
ata_std_dev_select(), ata_tf_to_host(), ata_busy_sleep(),
ata_wait_after_reset(), ata_wait_ready(), ata_bus_post_reset(),
ata_bus_softreset(), ata_bus_reset(), ata_std_softreset(),
sata_std_hardreset(), ata_fill_sg(), ata_fill_sg_dumb(),
ata_qc_prep(), ata_dump_qc_prep(), ata_data_xfer(),
ata_data_xfer_noirq(), ata_pio_sector(), ata_pio_sectors(),
atapi_send_cdb(), __atapi_pio_bytes(), atapi_pio_bytes(),
ata_hsm_ok_in_wq(), ata_hsm_qc_complete(), ata_hsm_move(),
ata_pio_task(), ata_qc_issue_prot(), ata_host_intr(),
ata_interrupt(), ata_std_ports()
* Make ata_pio_queue_task() global as it's now called from
libata-sff.c.
* Move SFF related stuff in include/linux/libata.h and
drivers/ata/libata.h into one place. While at it, move timing
constants into the global enum definition and fortify comments a
bit.
This patch strictly moves stuff around and as such doesn't cause any
functional difference.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
This patch implements libata.force module parameter which can
selectively override ATA port, link and device configurations
including cable type, SATA PHY SPD limit, transfer mode and NCQ.
For example, you can say "use 1.5Gbps for all fan-out ports attached
to the second port but allow 3.0Gbps for the PMP device itself, oh,
the device attached to the third fan-out port chokes on NCQ and
shouldn't go over UDMA4" by the following.
libata.force=2:1.5g,2.15:3.0g,2.03:noncq,udma4
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Move ata_set_mode() to libata-eh.c. ata_set_mode() is surely an EH
action and will be more tightly coupled with the rest of error
handling. Move it to libata-eh.c.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
ACPI spec (ver 3.0a, p289) requires IDE power on/off executes ACPI _PSx
methods. As recently most PATA drivers use libata, this patch adds _PSx
method support in libata. ACPI spec doesn't mention if SATA requires the
same _PSx method.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Acked-by: Len Brown <len.brown@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
Historically word 48 in the identify data was used to mean 32bit I/O
was supported for VLB IDE etc. ATA8 reassigns this word to the Trusted
Computing Group, where it is used for TCG features. This means that
an ATA8 TCG drive is going to trigger 32bit I/O on some systems which
will be funny.
Anyway we need to sort this out ready for ATA8 so:
- Reorder the ata.h header a bit so the ata_version function occurs early
in it
- Make dword_io check the ATA version
- Add an ATA8 version checking TCG presence test
While we are at it the current drafts have a flaw where it may not be
possible to disable TCG features at boot (and opt out of the trusted
model) as TCG intends because it relies on presence of a different
optional feature (DCS). Handle this in software by refusing the TCG
commands if libata.allow_tpm is not set. (We must make it possible
as some environments such as proprietary VDR devices will doubtless
want to use it to lock up content)
Finally as with CPRM print a warning so that the user knows they may
not be able to full access and use the device.
Signed-off-by: Alan Cox <alan@redhat.com>
Add two hooks - ata_acpi_dissociate() which is called during driver
detach after the whole host is shutdown and ata_acpi_on_disable()
which is called when a device is disabled.
Signed-off-by: Tejun heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Device Initiated Power Management, which is defined
in SATA 2.5 can be enabled for disks which support it.
This patch enables DIPM when the user sets the link
power management policy to "min_power".
Additionally, libata drivers can define a function
(enable_pm) that will perform hardware specific actions to
enable whatever power management policy the user set up
for Host Initiated Power management (HIPM).
This power management policy will be activated after all
disks have been enumerated and intialized. Drivers should
also define disable_pm, which will turn off link power
management, but not change link power management policy.
Documentation/scsi/link_power_management_policy.txt has additional
information.
Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
Add @timeout argument to ata_exec_internal[_sg](). If 0, default
timeout ata_probe_timeout is used.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Extend ata_acpi_associate_sata_port() such that it can handle PMP and
call it when PMP is attached and detached.
Build breakage when !CONFIG_ATA_ACPI was spotted and fixed by Petr
Vandrovec.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Petr Vandrovec <petr@vandrovec.name>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Hook PMP support into libata and enable it. Connect SCR and probing
functions, and update ata_dev_classify() to detect PMP.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Implement Port Multiplier support. To support PMP, a LLDD has to
supply ops->pmp_read() and pmp_write(). If non-null, ->pmp_attach and
->pmp_detach are called on PMP attach and detach, respectively.
->pmp_read/write() can be called while the port is frozen, so they
must be implemented by polling. This patch supplies several helpers
to ease ->pmp_read/write() implementation.
Also, irq_handler and error_handler must be PMP aware. Most of PMP
aware EH can be done by calling ata_pmp_do_eh() with appropriate
methods. PMP EH uses separate set of reset methods and this patch
implements standard prereset, hardreset and postreset methods.
This patch only implements PMP support. The next patch will integrate
PMP into the reset of libata and thus enable PMP support.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
AN serves multiple purposes. For ATAPI, it's used for media change
notification. For PMP, for downstream PHY status change notification.
Implement sata_async_notification() which demultiplexes AN.
To avoid unnecessary port events, ATAPI AN is not enabled if PMP is
attached but SNTF is not available.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Kriten Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Make a number of functions from libata-core.c and libata-eh.c global
to libata (drivers/ata/libata.h). These will be used by PMP.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Consider newly found class code while revalidating. PMP resetting
always results in valid class code and issuing PMP commands to
ATA/ATAPI device isn't very attractive. Add @new_class to
ata_dev_revalidate() and check class code for revalidation.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Add support for issuing ATA_16 passthru commands to ATAPI devices
managed by libata. It requires the previous CDB length fix patch.
A boot/module parameter, "atapi_passthru16=0" can be used to globally
disable this feature, if ever desired.
tj: restructured __ata_scsi_queuecmd() according to Jeff's suggestion.
Signed-off-by: Mark Lord <liml@rtr.ca>
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Make the following functions deal with ata_link instead of ata_port.
* ata_set_mode()
* ata_eh_autopsy() and related functions
* ata_eh_report() and related functions
* suspend/resume related functions
* ata_eh_recover() and related functions
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Make the following PHY-related functions to deal with ata_link instead
of ata_port.
* sata_print_link_status()
* sata_down_spd_limit()
* ata_set_sata_spd_limit() and friends
* sata_link_debounce/resume()
* sata_scr_valid/read/write/write_flush()
* ata_link_on/offline()
This patch introduces no behavior change.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
In most cases, when EH is scheduled, all in-flight commands are
aborted causing EH to kick in immediately. However, in some cases
(especially with PMP), it's unclear which commands are affected by the
error condition and although aborting all in-flight commands work, it
isn't optimal and may cause unnecessary disruption. On the other
hand, waiting for in-flight commands to drain themselves can take up
to 30seconds.
This patch implements EH fast drain to handle such situations. It
gives in-flight commands some time to finish up but doesn't wait for
too long. After EH is scheduled, fast drain timer is started and if
no other completion occurs in ATA_EH_FASTDRAIN_INTERVAL all in-flight
commands are aborted. If any completion occurred in the interval, the
port is given another interval to finish up itself.
Currently ATA_EH_FASTDRAIN_INTERVAL is 3 secs which should be enough
for finishing up most commands.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
SCSI scan may fail due to memory allocation failure even if EH is not
in progress. Due to use of GFP_ATOMIC in SCSI scan path, allocation
failure isn't too rare especially while probing multiple devices at
once which is the case when a bunch of devices are connected to PMP.
This patch moves SCSI scan failure detetion logic from
ata_scsi_hotplug() to ata_scsi_scan_host() and implement synchronous
scan behavior. The synchronous path sleeps briefly and repeats SCSI
scan if some devices aren't attached properly. It contains robust
retry loop to minimize the chance of device misdetection during boot
and falls back to async retry if everything fails.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Implement _GTM/_STM support. acpi_gtm is added to ata_port which
stores _GTM parameters over suspend/resume cycle. A new hook
ata_acpi_on_suspend() is responsible for storing _GTM parameters
during suspend. _STM is executed in ata_acpi_on_resume(). With this
change, invoking _GTF is safe on IDE hierarchy and acpi_sata check
before _GTF is removed.
ata_acpi_gtm() and ata_acpi_stm() implementation is taken from Alan
Cox's pata_acpi implementation. ata_acpi_gtm() is fixed such that the
result parameter is not shifted by sizeof(union acpi_object).
Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
This patch reimplements ACPI invocation such that, instead of
exporting ACPI details to the rest of libata, ACPI event handlers -
ata_acpi_on_resume() and ata_acpi_on_devcfg() - are used. These two
functions are responsible for determining whether specific ACPI method
is used and when.
On resume, _GTF is scheduled by setting ATA_DFLAG_ACPI_PENDING device
flag. This is done this way to avoid performing the action on wrong
device device (device swapping while suspended).
On every ata_dev_configure(), ata_acpi_on_devcfg() is called, which
performs _SDD and _GTF. _GTF is performed only after resuming and, if
SATA, hardreset as the ACPI spec specifies. As _GTF may contain
arbitrary commands, IDENTIFY page is re-read after _GTF taskfiles are
executed.
If one of ACPI methods fails, ata_acpi_on_devcfg() retries on the
first failure. If it fails again on the second try, ACPI is disabled
on the device. Note that successful configuration clears ACPI failed
status.
With all feature checks moved to the above two functions,
do_drive_set_taskfiles() is trivial and thus collapsed into
ata_acpi_exec_tfs(), which is now static and converted to return the
number of executed taskfiles to be used by ata_acpi_on_resume(). As
failures are handled properly, ata_acpi_push_id() now returns -errno
on errors instead of unconditional zero.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
* Add acpi_handle to ata_host and ata_port. Rename
ata_device->obj_handle to ->acpi_handle and move it above such that
it doesn't get cleared on reconfiguration.
* Replace ACPI node association which ata_acpi_associate() which is
called once during host initialization. Unlike the previous
implementation, ata_acpi_associate() uses ATA_FLAG_ACPI_SATA to
choose between IDE or SATA ACPI hierarchy and uses simple child look
up instead of recursive walk to match the nodes. This is way safer
and simpler. Please read the following message for more info.
http://article.gmane.org/gmane.linux.ide/17554
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
With STANDBYDOWN tracking added, libata.spindown_compat isn't
necessary anymore. If userspace shutdown(8) issues STANDBYNOW, libata
warns. If userspace shutdown(8) doesn't issue STANDBYNOW, libata does
the right thing. Userspace can tell whether kernel supports spindown
by testing whether sysfs node manage_start_stop exists as before.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Separate out ata_dev_reread_id() from ata_dev_revalidate().
ata_dev_reread_id() reads IDENTIFY page and determines whether the
same device is still there. ata_dev_revalidate() reconfigures after
reread completes. This will be used by ACPI update.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
This patch cleans up libata-acpi such that it looks similar to other
libata files. This patch doesn't introuce any behavior changes.
* make libata-acpi functions take ata_device instead of ata_port +
device index
* s/atadev/dev/
* de-indent local variable declarations
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
ACPI applies to both SATA and PATA. Drop the 'S' from the config
variable.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Now that libata uses sd->manage_start_stop, libata spins down disk on
shutdown. In an attempt to compensate libata's previous shortcoming,
some distros sync and spin down disks attached via libata in their
shutdown(8). Some disks spin back up just to spin down again on
STANDBYNOW1 if the command is issued when the disk is spun down, so
this double spinning down causes problem.
This patch implements module parameter libata.spindown_compat which,
when set to one (default value), prevents libata from spinning down
disks on shutdown thus avoiding double spinning down. Note that
libata spins down disks for suspend to mem and disk, so with
libata.spindown_compat set to one, disks should be properly spun down
in all cases without modifying shutdown(8).
shutdown(8) should be fixed eventually. Some drive do spin up on
SYNCHRONZE_CACHE even when their cache is clean. Those disks
currently spin up briefly when sd tries to shutdown the device and
then the machine powers off immediately, which can't be good for the
head. We can't skip SYNCHRONIZE_CACHE during shudown as it can be
dangerous data integrity-wise.
So, this spindown_compat parameter is already scheduled for removal by
the end of the next year and here's what shutdown(8) should do.
* Check whether /sys/modules/libata/parameters/spindown_compat
exists. If it does, write 0 to it.
* For each libata harddisk {
* Check whether /sys/class/scsi_disk/h:c:i:l/manage_start_stop
exists. Iff it doesn't, synchronize cache and spin the disk
down as before.
}
The above procedure will make shutdown(8) work properly with kernels
before this change, ones with this workaround and later ones without
it.
To accelerate shutdown(8) updates, if the compat mode is in use, this
patch prints BIG FAT warning for five seconds during shutdown (the
optimal interval to annoy the user just the right amount discovered by
hours of tireless usability testing).
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
All drivers are converted to new init model. Kill probe_ent,
ata_device_add() and ata_pci_init_native_mode().
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Reorganize ata_host_alloc() and its subroutines into the following
three functions.
* ata_host_alloc() : allocates host and its ports. shost is not
registered automatically.
* ata_scsi_add_hosts() : allocates and adds shosts associated with an
ATA host. Used by ata_host_register().
* ata_host_register() : takes a fully initialized ata_host structure
and registers it to libata layer and probes it.
Only ata_host_alloc() and ata_host_register() are exported.
ata_device_add() is rewritten using the above functions. This patch
does not introduce any observable behavior change. Things worth
mentioning.
* print_id is assigned at registration time and LLDs are allowed to
overallocate ports and reduce host->n_ports during initialization.
ata_host_register() will throw away unused ports automatically.
* All SCSI host initialization stuff now resides in
ata_scsi_add_hosts() in libata-scsi.c, where it should be.
* ipr is now the only user of ata_host_init(). Either kill it by
converting ipr to use ata_host_alloc() and friends or rename and
move it to libata-scsi.c
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Not yet ready to turn on ATA ACPI by default, for either PATA or SATA.
Also, rename the global-scope module parameter variable 'noacpi' to
something more libata-specific, reducing the potential for namespace
collision.
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Somehow the sis_info133 external definition ended up in libata.h and that
was included by both drivers. However libata.h contains libata-* specific
internals and clashing defines like DRV_NAME so this makes a mess. Move
the extern into the C file and remove the warnings
[akpm@linux-foundation.org: create sis.h to avoid extern-decl-in-C]
Signed-off-by: Alan Cox <alan@redhat.com>
Cc: Jeff Garzik <jeff@garzik.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Make ata_down_xfermask_limit() accept @sel instead of @force_pio0.
@sel selects how the xfermask limit will be adjusted. The following
selectors are defined.
* ATA_DNXFER_PIO : only speed down PIO
* ATA_DNXFER_DMA : only speed down DMA, don't cause transfer mode change
* ATA_DNXFER_40C : apply 40c cable limit
* ATA_DNXFER_FORCE_PIO : force PIO
* ATA_DNXFER_FORCE_PIO0 : force PIO0 (same as original with @force_pio0 == 1)
* ATA_DNXFER_ANY : same as original with @force_pio0 == 0
Currently, only ANY and FORCE_PIO0 are used to maintain the original
behavior. Other selectors will be used later to improve EH speed down
sequence.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
_SDD (Set Device Data) is an ACPI method that is used to tell the
firmware what the identify data is of the device that is attached to
the port. It is an optional method, and it's ok for it to be missing.
Because of this, we always return success from the routine that calls
this method, even if the execution fails.
Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
(cherry picked from 39aa79e0a1f5f2e28aa341f035940746a98b45b1 commit)
_GTF is an acpi method that is used to reinitialize the drive. It returns
a task file containing ata commands that are sent back to the drive to restore
it to boot up defaults.
Signed-off-by: Kristen Carlson Accardi <kristen.c.accardi@intel.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
(cherry picked from 9c69cab24b51a89664f4c0dfaf8a436d32117624 commit)
Static code shouldn't be used from other modules.
drivers/built-in.o: In function `sis_init_one':
sata_sis.c:(.text+0x7634cd): undefined reference to `sis_info133'
sata_sis.c:(.text+0x7634d6): undefined reference to `sis_info133'
While I was at it, I also moved the prototype of this struct to a header
file.
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Cc: Jeff Garzik <jeff@garzik.org>
Cc: Tejun Heo <htejun@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
libata switched to IRQ-driven IDENTIFY when IRQ-driven PIO was
introduced. This has caused a lot of problems including device
misdetection and phantom device.
ATA_FLAG_DETECT_POLLING was added recently to selectively use polling
IDENTIFY on problemetic drivers but many controllers and devices are
affected by this problem and trying to adding ATA_FLAG_DETECT_POLLING
for each such case is diffcult and not very rewarding.
This patch makes libata always use polling IDENTIFY. This is
consistent with libata's original behavior and drivers/ide's behavior.
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Tejun Heo