Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

MFC r256547 (by smh):
Added 4K quirks for Corsair Neutron GTX SSD's

MFC r257054:
Some microoptimizations for da and ada drivers:
- Replace ordered_tag_count counter with single flag;
- From da remove outstanding_cmds counter, duplicating pending_ccbs list;
- From da_softc remove unused links field.

MFC r256836:
Remove hard limit on number of BIOs handled with one ATA TRIM request.

MFC r256552:
Unify periph invalidation and destruction reporting.
Print message containing device model and serial number on invalidation.

MFC r254329 (by smh):
Added 4K quirks for:-
* OCZ Agility 2 SSDs
* Marvell SSDs
* Intel X25-M Series SSDs

MFC r249466, r249481, r250025:
Remove multilevel freezing mechanism, implemented to handle specifics of
the ATA/SATA error recovery, when post-reset recovery commands should be
allocated when queues are already full of payload requests. Instead of
removing frozen CCBs with specified range of priorities from the queue
to provide free openings, use simple hack, allowing explicit CCBs over-
allocation for requests with priority higher (numerically lower) then
CAM_PRIORITY_OOB threshold.

Simplify CCB allocation logic by removing SIM-level allocation queue.
After that SIM-level queue manages only CCBs execution, while allocation
logic is localized within each single device.

MFC r253752:
Fix returning incorrect bio_resid value with failed BIO_DELETE requests.
Neither residual length reported for ATA/SCSI command nor one from another
BIO_DELETE request are in any way related to the value to be returned.

MFC r249981:
Remove ADA_FLAG_PACK_INVALID flag. Since ATA disks have no concept of media
change it only duplicates CAM_PERIPH_INVALID flag, so we can use last one.

Slightly cleanup DA_FLAG_PACK_INVALID use.

MFC r253724:
Synchronize device cache on close only if there were some write operations.
While these operations are not really needed otherwise, at least for SCSI
they may cause extra errors if some other initiator holds write exclusive
reservation on the LUN (SYNCHRONIZE CACHE handled as "write" operation).

MFC r253091:
Added 4K QUIRK for OCZ Vertex 4 SSDs

MFC r249940:
Teach GEOM and CAM about the difference between the max "size" of r/w and delete
requests.

MFC r252657:
Bump disk(9) ABI version to signify the addition of d_delmaxsize.

Make the addition of the d_delmaxsize binary compatible. This allows storage
drivers compiled for 9.0 and 9.1 to work by preserving the ABI for disks.

Reviewed by: mav

MFC r251792:
Restore use of polling mode for disk cache flush in case of kernel panic.
While I am not sure that any extra hardware access is a good idea after
panic, that is an existing behaviour that should better work correctly.

Merge the second part of the unmapped I/O changes. This enables the
infrastructure in the block layer and UFS filesystem as well as a few
drivers. The list of MFC revisions is long, so I won't quote changelogs.

r248508,248510,248511,248512,248514,248515,248516,248517,248518,
248519,248520,248521,248550,248568,248789,248790,249032,250936

Submitted by: kib
Approved by: kib
Obtained from: Netflix

MFC r249205:
Replicate r245306 from SCSI to ATA. The problem didn't appear so far,
covered by multilevel freeze mechanism, but it is better to be safe.

MFC r251061:
More 4k quirks for SSD's

MFC r250792:
Added output of device QUIRKS for CAM and AHCI devices during boot.

Enhanced BIO_DELETE support for CAM SCSI to add ATA_TRIM support.

Disable CAM BIO queue sorting for non-rotating media by default.

MFC r249939 Added available delete methods discovery during device probe
MFC r249941 Automatically disable BIO queue sorting for non-rotating media
MFC r250033 Correct comment typo's
MFC r250179 Update probe flow so that devices with lbp can also disable disksort
MFC r250180 Fix probe in progress check in dareprobe
MFC r250181 Check for ATA Information VPD before querying for ATA
MFC r250183 Enable CAM SCSI to choice ATA TRIM during autodetection
MFC r250967 Enforce validation on the selected delete method via sysctl

MFC r249934:
Updated TRIM calculations in CAM ATA to be based off ATA_DSM_* defines

MFC r248922:
Add the ability to enable / disable sorting of BIO requests

MFC: r249199

Unbreak ATA_NO_48BIT_DMA with ATA_CAM by treating 48-bit DMA as an
optional property with PATA transport.

Reviewed by: mav

MFC r249347:
------------------------------------------------------------------------
r249347 | ken | 2013-04-10 16:12:21 -0600 (Wed, 10 Apr 2013) | 22 lines

Add a callback to the ada(4) driver so that it knows when GEOM has released
references to it.

This is the functional equivalent to change r237518, which added this
functionality to the cd(4) and da(4) drivers.

This fix prevents a panic caused by GEOM calling adaopen() while the device
is going away. We now keep the device around until GEOM has finished
cleaning up its state.

ata_da.c: In adaregister(), add a d_gone callback to the GEOM disk
structure registered for the ada driver. Increment the
peripheral reference count for GEOM.

Add a new callback, adadiskgonecb(), that GEOM calls when
it is done with its resources. This callback releases the
reference acquired in adaregister().

Submitted by: Po-Li Soong
Sponsored by: Spectra Logic

MFC r249106:
Replace some direct mutex operations with wrappers.

MFC r249105:
Remove extra NULL checks. d_drv1 can never be NULL during periph life cycle.

MFC r248872, r249048:
Make pre-shutdown flush and spindown routines to not use xpt_polled_action(),
but execute the commands in regular way. There is no any reason to cook CPU
while the system is still fully operational. After this change polling in
CAM is used only for kernel dumping.

MFC r248868, r248874:
Implement CAM_PERIPH_FOREACH() macro, safely iterating over the list of
driver's periphs, acquiring and releaseing periph references while doing it.

Use it to iterate over the lists of ada and da periphs when flushing caches
and putting devices to sleep on shutdown and suspend. Previous code could
panic in theory if some device disappear in the middle of the process.

MFC r227293 (by ed):
Mark MALLOC_DEFINEs static that have no corresponding MALLOC_DECLAREs.

This means that their use is restricted to a single C file.

MFC: r227309 (partial)

Mark all SYSCTL_NODEs static that have no corresponding SYSCTL_DECLs.

The SYSCTL_NODE macro defines a list that stores all child-elements of
that node. If there's no SYSCTL_DECL macro anywhere else, there's no
reason why it shouldn't be static.

MFC r238379, r238382 (by bruefer):
Renamed the kern.cam.da.da_send_ordered sysctl and tunable to
kern.cam.da.send_ordered, more in line with the other da sysctls/tunables.
Renamed the kern.cam.ada.ada_send_ordered sysctl and tunable to
kern.cam.ada.send_ordered, more in line with the other da sysctls/tunables.

PR: 169765

MFC r241784:
Adds 4K quirks for the some SSD's which all perform better when 4K
aligned and only except 4K deletes (TRIM).

PR: kern/169974
Approved by: cperciva (implicit)

MFC r241485:
Protect xpt_getattr() calls with the SIM lock and assert that.

MFC r241404:
Remove 'periph == NULL' check from bunch of periph drivers.
This condition can never be true as functions are called from single place
and the checks just pollute the code and confuse Clang Static Analyzer.

MFC r241305: ata_da: set disk::d_ident from serial number

MFC r236814:
One more major cam_periph_error() rewrite to improve error handling and
reporting. It includes:
- removing of error messages controlled by bootverbose, replacing them
with more universal and informative debugging on CAM_DEBUG_INFO level,
that is now built into the kernel by default;
- more close following to the arguments submitted by caller, such as
SF_PRINT_ALWAYS, SF_QUIET_IR and SF_NO_PRINT; consumer knows better which
errors are usual/expected at this point and which are really informative;
- adding two new flags SF_NO_RECOVERY and SF_NO_RETRY to allow caller
specify how much assistance it needs at this point; previously consumers
controlled that by not calling cam_periph_error() at all, but that made
behavior inconsistent and debugging complicated;
- tuning debug messages and taken actions order to make debugging output
more readable and cause-effect relationships visible;
- making camperiphdone() (common device recovery completion handler) to
also use cam_periph_error() in most cases, instead of own dumb code;
- removing manual sense fetching code from cam_periph_error(); I was told
by number of people that it is SIM obligation to fetch sense data, so this
code is useless and only significantly complicates recovery logic;
- making ada, da and pass driver to use cam_periph_error() with new limited
recovery options to handle error recovery and debugging in common way;
as one of results, CAM_REQUEUE_REQ and other retrying statuses are now
working fine with pass driver, that caused many problems before.
- reverting r186891 by raj@ to avoid burning few seconds in tight DELAY()
loops on device probe, while device simply loads media; I think that problem
may already be fixed in other way, and even if it is not, solution must be
different.

Sponsored by: iXsystems, Inc.

MFC r236604, r236639:
Do not reinvent a wheel and let default error handler do its job.

MFC r236602, r236613:
Tune and add some missing CAM_DEBUG() points for better consistency.

NFC r236393:
Use AC_GETDEV_CHANGED async to notify ada driver about DMA and NCQ status
change. Now that allows switching between PIO and DMA modes on the fly.

MFC r235897:
- Add low-level support for SATA Enclosure Management Bridge (SEMB)
devices -- SATA equivalents of the SCSI SES/SAF-TE devices.
- Add some utility functions for SCSI SAF-TE devices access.

Sponsored by: iXsystems, Inc.

MFC r234414:
Alike to SCSI make adaclose() to not return error if device gone.
This fixes KASSERT panic inside GEOM if kernel built with INVARIANTS.

MFc r229288:
Remove unneeded checks for CAM_DEV_QFRZN after cam_periph_runccb() call.
cam_periph_runccb() since the beginning checks it and releases device queue.
After r203108 it even clears CAM_DEV_QFRZN flag after that to avoid double
release, so removed code is unreachable now.

MFC r230921:
Insert ordered command every 1/4 of the current command timeout, not 1/4
of the default one.

Without this change setting kern.cam.ada.default_timeout to 1 instead of 30
allowed me to trigger several false positive command timeouts under heavy
ZFS load on a SiI3132 siis(4) controller with 5 HDDs on a port multiplier.

MFC r228819:
Update list of 4K physical sector hard drives.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Higher-priority initialization request can eat request scheduling done from
adaclose(). Add immediate_priority check into adaschedule() to restore it.

Approved by: re (kib)
MFC after: 1 week

Add control for ATA disk read-ahead, alike to the previously added write
cache control. Some controller BIOS'es tend to disable read-ahead, that
dramatically reduces read performance. Previously ata(4) always enabled
read-ahead unconditionally.

Approved by: re (kib)

Do not try to execute FLUSHCACHE on close and print extra messages for
invalidated (considered lost) ada device. Exactly same already done for
the da devices.

Approved by: re (kib)
MFC after: 1 week

Fix a typo in adagetattr() from r223089. In particular, this restores
the ability to use ahci(4) for kernel dumps.

Plumb device physical path reporting from CAM devices, through GEOM and
DEVFS, and make it accessible via the diskinfo utility.

Extend GEOM's generic attribute query mechanism into generic disk consumers.
sys/geom/geom_disk.c:
sys/geom/geom_disk.h:
sys/cam/scsi/scsi_da.c:
sys/cam/ata/ata_da.c:
- Allow disk providers to implement a new method which can override
the default BIO_GETATTR response, d_getattr(struct bio *). This
function returns -1 if not handled, otherwise it returns 0 or an
errno to be passed to g_io_deliver().

sys/cam/scsi/scsi_da.c:
sys/cam/ata/ata_da.c:
- Don't copy the serial number to dp->d_ident anymore, as the CAM XPT
is now responsible for returning this information via
d_getattr()->(a)dagetattr()->xpt_getatr().

sys/geom/geom_dev.c:
- Implement a new ioctl, DIOCGPHYSPATH, which returns the GEOM
attribute "GEOM::physpath", if possible. If the attribute request
returns a zero-length string, ENOENT is returned.

usr.sbin/diskinfo/diskinfo.c:
- If the DIOCGPHYSPATH ioctl is successful, report physical path
data when diskinfo is executed with the '-v' option.

Submitted by: will
Reviewed by: gibbs
Sponsored by: Spectra Logic Corporation

Add generic attribute change notification support to GEOM.

sys/sys/geom/geom.h:
Add a new attrchanged method field to both g_class
and g_geom.

sys/sys/geom/geom.h:
sys/geom/geom_event.c:
- Provide the g_attr_changed() function that providers
can use to advertise attribute changes.
- Perform delivery of attribute change notifications
from a thread context via the standard GEOM event
mechanism.

sys/geom/geom_subr.c:
Inherit the attrchanged method from class to geom (class instance).

sys/geom/geom_disk.c:
Provide disk_attr_changed() to provide g_attr_changed() access
to consumers of the disk API.

sys/cam/scsi/scsi_pass.c:
sys/cam/scsi/scsi_da.c:
sys/geom/geom_dev.c:
sys/geom/geom_disk.c:
Use attribute changed events to track updates to physical path
information.

sys/cam/scsi/scsi_da.c:
Add AC_ADVINFO_CHANGED to the registered asynchronous CAM
events for this driver. When this event occurs, and
the updated buffer type references our physical path
attribute, emit a GEOM attribute changed event via the
disk_attr_changed() API.

sys/cam/scsi/scsi_pass.c:
Add AC_ADVINFO_CHANGED to the registered asynchronous CAM
events for this driver. When this event occurs, update
the physical patch devfs alias for this pass instance.

Submitted by: gibbs
Sponsored by: Spectra Logic Corporation

Increase maximum supported number of ranges per TRIM command from 256 to 512
to use full potential of Intel X25-M SSDs. On synthetic test with 32K ranges
it gives about 20% speedup, which probably costs more then 2K of RAM.

When possible, join ranges of subsequest BIO_DELETE requests to handle more
(up to 2048 instead of 256 or even 64) of them with single TRIM request.

OCZ Vertex2/Vertex3 SSDs can handle no more then 64 ranges per TRIM request.
Due to lack of BIO_DELETE clustering now, it means that we could delete no
more then 2MB per request (on FS with 32K block) with limited request rate.
This change increases delete rate on Vertex2 from 250MB/s to 950MB/s.

Add quirks to hint 4K physical sector (Advanced Format) for ATA disks not
reporting it properly (none? of known disks now).

Hitachi and WDC AF disks seem could be identified more or less formally.
For Seagate and Samsung enumerate some found models/series.
For other disks it can be forced with kern.cam.ada.X.quirks=1 tunable.

- Add shim to simplify migration to the CAM-based ATA. For each new adaX
device in /dev/ create symbolic link with adY name, trying to mimic old ATA
numbering. Imitation is not complete, but should be enough in most cases to
mount file systems without touching /etc/fstab.
- To know what behavior to mimic, restore ATA_STATIC_ID option in cases
where it was present before.
- Add some more details to UPDATING.

Add basic support for DMA-capable ATA disks on DMA-incapable controller.
This is really rare situation these days, but still may happen in embedded.

Remove some used variables.

Found with: Clang Static Analyzer

Make ada(4) driver put ATA disks into sleep state on suspend.

Submitted by: jkim (original version)

Make CAM report devices with ATA/SATA transport to devstat(9) as IDE.

Fix typo in write_cache tunable name and move TUNABLE_INT_FETCH() out of
the SIM lock to fix WITNESS warning.

Reported by: jh

- Add kern.cam.ada.X.write_cache tunables/sysctls to control write caching
on per-device basis.
- While adding support for per-device sysctls, merge from graid branch
support for ADA_TEST_FAILURE kernel option, which opens few more sysctl,
allowing to simulate read and write errors for testing purposes.

Make ada(4) driver to control device write cache, same as ata(4) does.
Add kern.cam.ada.write_cache sysctl/tunable to control it alike hw.ata.wc.

Add the disk ident and a human-meaningful description (here, the disk model
string) to the geom_disk config XML so that they are easily accessible from
userland.

MFC after: 1 week

Mostly revert r203420, and add similar functionality into ada(4) since the
existing code caused problems with some SCSI controllers.

A new sysctl kern.cam.ada.spindown_shutdown has been added that controls
whether or not to spin-down disks when shutting down.
Spinning down the disks unloads/parks the heads - this is
much better than removing power when the disk is still
spinning because otherwise an Emergency Unload occurs which may cause damage
to the actuator.

PR: kern/140752
Submitted by: olli
Reviewed by: arundel
Discussed with: mav
MFC after: 2 weeks

Correct bioq_disksort so that bioq_insert_tail() offers barrier semantic.
Add the BIO_ORDERED flag for struct bio and update bio clients to use it.

The barrier semantics of bioq_insert_tail() were broken in two ways:

o In bioq_disksort(), an added bio could be inserted at the head of
the queue, even when a barrier was present, if the sort key for
the new entry was less than that of the last queued barrier bio.

o The last_offset used to generate the sort key for newly queued bios
did not stay at the position of the barrier until either the
barrier was de-queued, or a new barrier (which updates last_offset)
was queued. When a barrier is in effect, we know that the disk
will pass through the barrier position just before the
"blocked bios" are released, so using the barrier's offset for
last_offset is the optimal choice.

sys/geom/sched/subr_disk.c:
sys/kern/subr_disk.c:
o Update last_offset in bioq_insert_tail().

o Only update last_offset in bioq_remove() if the removed bio is
at the head of the queue (typically due to a call via
bioq_takefirst()) and no barrier is active.

o In bioq_disksort(), if we have a barrier (insert_point is non-NULL),
set prev to the barrier and cur to it's next element. Now that
last_offset is kept at the barrier position, this change isn't
strictly necessary, but since we have to take a decision branch
anyway, it does avoid one, no-op, loop iteration in the while
loop that immediately follows.

o In bioq_disksort(), bypass the normal sort for bios with the
BIO_ORDERED attribute and instead insert them into the queue
with bioq_insert_tail(). bioq_insert_tail() not only gives
the desired command order during insertion, but also provides
barrier semantics so that commands disksorted in the future
cannot pass the just enqueued transaction.

sys/sys/bio.h:
Add BIO_ORDERED as bit 4 of the bio_flags field in struct bio.

sys/cam/ata/ata_da.c:
sys/cam/scsi/scsi_da.c
Use an ordered command for SCSI/ATA-NCQ commands issued in
response to bios with the BIO_ORDERED flag set.

sys/cam/scsi/scsi_da.c
Use an ordered tag when issuing a synchronize cache command.

Wrap some lines to 80 columns.

sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c
sys/geom/geom_io.c
Mark bios with the BIO_FLUSH command as BIO_ORDERED.

Sponsored by: Spectra Logic Corporation
MFC after: 1 month

Export PCI IDs of ATA/SATA controllers through CAM and ata(4) layers to
GEOM. This information needed for proper soft-RAID's on-disk metadata
reading and writing.

Change ad_firmware_geom_adjust() to operate on a struct disk * only and
hook it up to ada(4) also. While at it, rename *ad_firmware_geom_adjust()
to *ata_disk_firmware_geom_adjust() etc now that these are no longer
limited to ad(4).

Reviewed by: mav
MFC after: 3 days

MFp4:
Move PI_TAG_ABLE check from ada driver to ATA XPT.

- Use separate buffer for identify data fetching. We can't use main buffer
here if device already running, as data need to be formatted before use.
- Remove some saved_ccb variables. They are unused now.

MFp4: Large set of CAM inprovements.

- Unify bus reset/probe sequence. Whenever bus attached at boot or later,
CAM will automatically reset and scan it. It allows to remove duplicate
code from many drivers.
- Any bus, attached before CAM completed it's boot-time initialization,
will equally join to the process, delaying boot if needed.
- New kern.cam.boot_delay loader tunable should help controllers that
are still unable to register their buses in time (such as slow USB/
PCCard/ CardBus devices), by adding one more event to wait on boot.
- To allow synchronization between different CAM levels, concept of
requests priorities was extended. Priorities now split between several
"run levels". Device can be freezed at specified level, allowing higher
priority requests to pass. For example, no payload requests allowed,
until PMP driver enable port. ATA XPT negotiate transfer parameters,
periph driver configure caching and so on.
- Frozen requests are no more counted by request allocation scheduler.
It fixes deadlocks, when frozen low priority payload requests occupying
slots, required by higher levels to manage theit execution.
- Two last changes were holding proper ATA reinitialization and error
recovery implementation. Now it is done: SATA controllers and Port
Multipliers now implement automatic hot-plug and should correctly
recover from timeouts and bus resets.
- Improve SCSI error recovery for devices on buses without automatic sense
reporting, such as ATAPI or USB. For example, it allows CAM to wait, while
CD drive loads disk, instead of immediately return error status.
- Decapitalize diagnostic messages and make them more readable and sensible.
- Teach PMP driver to limit maximum speed on fan-out ports.
- Make boot wait for PMP scan completes, and make rescan more reliable.
- Fix pass driver, to return CCB to user level in case of error.
- Increase number of retries in cd driver, as device may return several UAs.

Add BIO_DELETE support to ada(4):
- For SSDs use TRIM feature of DATA SET MANAGEMENT command, as defined by
ACS-2 specification working draft.
- For CompactFlash use CFA ERASE command, same as ad(4) does.

With this patch, `newfs -E /dev/ada1` was able to restore write speed of
my heavily weared OCZ Vertex SSD (firmware 1.4) up to the initial level
for the most part of it's capacity. Previous 1.3 firmware, even reportiong
TRIM capabilty bit set, was not working, reporting ABORT error for every
DSM command.

I have no idea whether it is normal, but for some reason it takes 200ms
to handle any TRIM command on this drive, that was making delete extremely
slow. But TRIM command is able to accept long list of LBAs and the length of
that list seems doesn't affect it's execution time. Implemented request
clusting algorithm allowed me to rise delete rate up to reasonable numbers,
when many parallel DELETE requests running.

Report stripe size only if physical sector size is not equal to logical.

MFp4:
If we panicked with SIM lock held, do not try to flush caches.
Extra lock recursing will not make debugging easier.

MFp4:
- Move tagged queueing control from ADA to ATA XPT. It allows to control
device command queue length correctly. First step to support < 32 tags.
- Limit queue for non-tagged devices by 2 slots for ahci(4) and siis(4).
- Implement quirk matching for ATA devices.
- Move xpt_schedule_dev_sendq() from header to source file.
- Move delayed queue shrinking to the more expected place - element freeing.
- Remove some SCSIsms in ATA.

MFp4:
- Remove CAM_PERIPH_POLLED flag. It is broken by design. Polling can't be
periph flag. May be SIM, may be CCB, but now it works fine just without it.
- Remove check unused for at least five years. If we will ever have non-BIO
devices in CAM, this check is smallest of what we will need.
- If several controllers complete requests same time, call swi_sched()
only once.

MFp4:
- Add support for sector size > 512 bytes and physical sector of several
logical sectors, introduced by ATA-7 specification.
- Remove some obsoleted code.

MFp4:
- Reduce code duplication in ATA XPT and PMP driver.
- Move PIO size setting from ada driver to ATA XPT. It is XPT business
to negotiate transfer details. ada driver is now stateless.
- Report PIO size to SIM. It is required for correct PATA SIM operation.
- Tune PMP scan timings. It workarounds some problems with SiI.
- If reset hapens during PMP initialization - restart it.
- Introduce early-initialized periph drivers, which are used during initial
scan process. Use it for xpt, probe, aprobe and pmp. It gives pmp chance
to finish scan before mountroot and numerate devices in right order.

Replace most of priority numbers with defines. No logical changes.

MFp4:
Add support for PIO-only devices.
Fix maxio values and 256 sectors transactions for 28bits commands.
Implement periodic ordered commands insertion, sames as da driver does.
Remove some SCSIsms.

Export disk serial numbers for adaX disks.

Reviewed by: mav
MFC after: 3 days

Short ATA command format has 28bit address, not 36bit.
Rename ata_36bit_cmd() into ata_28bit_cmd(), while it didn't become legacy.

MFC after: 2 days

ATA_FLUSHCACHE is a 36bit format command, not 48.

Fix copy-paste bug. Use regular non-polled mode for executing FLUSHCACHE
command on disk close.

Approved by: re (implicitly)

Separate the parallel scsi knowledge out of the core of the XPT, and
modularize it so that new transports can be created.

Add a transport for SATA

Add a periph+protocol layer for ATA

Add a driver for AHCI-compliant hardware.

Add a maxio field to CAM so that drivers can advertise their max
I/O capability. Modify various drivers so that they are insulated
from the value of MAXPHYS.

The new ATA/SATA code supports AHCI-compliant hardware, and will override
the classic ATA driver if it is loaded as a module at boot time or compiled
into the kernel. The stack now support NCQ (tagged queueing) for increased
performance on modern SATA drives. It also supports port multipliers.

ATA drives are accessed via 'ada' device nodes. ATAPI drives are
accessed via 'cd' device nodes. They can all be enumerated and manipulated
via camcontrol, just like SCSI drives. SCSI commands are not translated to
their ATA equivalents; ATA native commands are used throughout the entire
stack, including camcontrol. See the camcontrol manpage for further
details. Testing this code may require that you update your fstab, and
possibly modify your BIOS to enable AHCI functionality, if available.

This code is very experimental at the moment. The userland ABI/API has
changed, so applications will need to be recompiled. It may change
further in the near future. The 'ada' device name may also change as
more infrastructure is completed in this project. The goal is to
eventually put all CAM busses and devices until newbus, allowing for
interesting topology and management options.

Few functional changes will be seen with existing SCSI/SAS/FC drivers,
though the userland ABI has still changed. In the future, transports
specific modules for SAS and FC may appear in order to better support
the topologies and capabilities of these technologies.

The modularization of CAM and the addition of the ATA/SATA modules is
meant to break CAM out of the mold of being specific to SCSI, letting it
grow to be a framework for arbitrary transports and protocols. It also
allows drivers to be written to support discrete hardware without
jeopardizing the stability of non-related hardware. While only an AHCI
driver is provided now, a Silicon Image driver is also in the works.
Drivers for ICH1-4, ICH5-6, PIIX, classic IDE, and any other hardware
is possible and encouraged. Help with new transports is also encouraged.

Submitted by: scottl, mav
Approved by: re