Dcoumentation has been added by parsing through git commit history and
reading code. This might be useful for scripting and tracking changes in
the ABI.

I do not have complete descriptions for the following 3 attributes; they
have been annotated with the comment [to be documented] -

        /sys/class/scsi_host/hostX/ahci_port_cmd
        /sys/class/scsi_host/hostX/ahci_host_caps
        /sys/class/scsi_host/hostX/ahci_host_cap2

Signed-off-by: Aishwarya Pant <aishp...@gmail.com>
---
 Documentation/ABI/testing/sysfs-block-device    | 58 ++++++++++++++++
 Documentation/ABI/testing/sysfs-class-scsi_host | 89 +++++++++++++++++++++++++
 2 files changed, 147 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-block-device

diff --git a/Documentation/ABI/testing/sysfs-block-device 
b/Documentation/ABI/testing/sysfs-block-device
new file mode 100644
index 000000000000..82ef6eab042d
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-block-device
@@ -0,0 +1,58 @@
+What:          /sys/block/*/device/sw_activity
+Date:          Jun, 2008
+KernelVersion: v2.6.27
+Contact:       linux-...@vger.kernel.org
+Description:
+               (RW) Used by drivers which support software controlled activity
+               LEDs.
+
+               It has the following valid values:
+
+               0       OFF - the LED is not activated on activity
+               1       BLINK_ON - the LED blinks on every 10ms when activity is
+                       detected.
+               2       BLINK_OFF - the LED is on when idle, and blinks off
+                       every 10ms when activity is detected.
+
+               Note that the user must turn sw_activity OFF it they wish to
+               control the activity LED via the em_message file.
+
+
+What:          /sys/block/*/device/unload_heads
+Date:          Sep, 2008
+KernelVersion: v2.6.28
+Contact:       linux-...@vger.kernel.org
+Description:
+               (RW) Hard disk shock protection
+
+               Writing an integer value to this file will take the heads of the
+               respective drive off the platter and block all I/O operations
+               for the specified number of milliseconds.
+
+               - If the device does not support the unload heads feature,
+                 access is denied with -EOPNOTSUPP.
+               - The maximal value accepted for a timeout is 30000
+                 milliseconds.
+               - A previously set timeout can be cancelled and disk can resume
+                 normal operation immediately by specifying a timeout of 0.
+               - Some hard drives only comply with an earlier version of the
+                 ATA standard, but support the unload feature nonetheless.
+                 There is no safe way Linux can detect these devices, so this
+                 is not enabled by default. If it is known that your device
+                 does support the unload feature, then you can tell the kernel
+                 to enable it by writing -1. It can be disabled again by
+                 writing -2.
+               - Values below -2 are rejected with -EINVAL
+
+               For more information, see
+               Documentation/laptops/disk-shock-protection.txt
+
+
+What:          /sys/block/*/device/ncq_prio_enable
+Date:          Oct, 2016
+KernelVersion: v4.10
+Contact:       linux-...@vger.kernel.org
+Description:
+               (RW) Write to the file to turn on or off the SATA ncq (native
+               command queueing) support. By default this feature is turned
+               off.
diff --git a/Documentation/ABI/testing/sysfs-class-scsi_host 
b/Documentation/ABI/testing/sysfs-class-scsi_host
index 0eb255e7db12..bafc59fd7b69 100644
--- a/Documentation/ABI/testing/sysfs-class-scsi_host
+++ b/Documentation/ABI/testing/sysfs-class-scsi_host
@@ -27,3 +27,92 @@ Description: This file contains the current status of the 
"SSD Smart Path"
                the direct i/o path to physical devices.  This setting is
                controller wide, affecting all configured logical drives on the
                controller.  This file is readable and writable.
+
+What:          /sys/class/scsi_host/hostX/link_power_management_policy
+Date:          Oct, 2007
+KernelVersion: v2.6.24
+Contact:       linux-...@vger.kernel.org
+Description:
+               (RW) This parameter allows the user to read and set the link
+               (interface) power management.
+
+               There are four possible options:
+
+               min_power: Tell the controller to try to make the link use the
+               least possible power when possible. This may sacrifice some
+               performance due to increased latency when coming out of lower
+               power states.
+
+               max_performance: Generally, this means no power management.
+               Tell the controller to have performance be a priority over power
+               management.
+
+               medium_power: Tell the controller to enter a lower power state
+               when possible, but do not enter the lowest power state, thus
+               improving latency over min_power setting.
+
+               med_power_with_dipm: Identical to the existing medium_power
+               setting except that it enables dipm (device initiated power
+               management) on top, which makes it match the Windows IRST (Intel
+               Rapid Storage Technology) driver settings. This setting is also
+               close to min_power, except that:
+               a) It does not use host-initiated slumber mode, but it does
+               allow device-initiated slumber
+               b) It does not enable low power device sleep mode (DevSlp).
+
+What:          /sys/class/scsi_host/hostX/em_message
+What:          /sys/class/scsi_host/hostX/em_message_type
+Date:          Jun, 2008
+KernelVersion: v2.6.27
+Contact:       linux-...@vger.kernel.org
+Description:
+               em_message: (RW) Enclosure management support. For the LED
+               protocol, writes and reads correspond to the LED message format
+               as defined in the AHCI spec.
+
+               The user must turn sw_activity (under /sys/block/*/device/) OFF
+               it they wish to control the activity LED via the em_message
+               file.
+
+               em_message_type: (RO) Displays the current enclosure management
+               protocol that is being used by the driver (for eg. LED, SAF-TE,
+               SES-2, SGPIO etc).
+
+What:          /sys/class/scsi_host/hostX/ahci_port_cmd
+What:          /sys/class/scsi_host/hostX/ahci_host_caps
+What:          /sys/class/scsi_host/hostX/ahci_host_cap2
+Date:          Mar, 2010
+KernelVersion: v2.6.35
+Contact:       linux-...@vger.kernel.org
+Description:
+               [to be documented]
+
+What:          /sys/class/scsi_host/hostX/ahci_host_version
+Date:          Mar, 2010
+KernelVersion: v2.6.35
+Contact:       linux-...@vger.kernel.org
+Description:
+               (RO) Display the version of the AHCI spec implemented by the
+               host.
+
+What:          /sys/class/scsi_host/hostX/em_buffer
+Date:          Apr, 2010
+KernelVersion: v2.6.35
+Contact:       linux-...@vger.kernel.org
+Description:
+               (RW) Allows access to AHCI EM (enclosure management) buffer
+               directly if the host supports EM.
+
+               For eg. the AHCI driver supports SGPIO EM messages but the
+               SATA/AHCI specs do not define the SGPIO message format of the EM
+               buffer. Different hardware(HW) vendors may have different
+               definitions. With the em_buffer attribute, this issue can be
+               solved by allowing HW vendors to provide userland drivers and
+               tools for their SGPIO initiators.
+
+What:          /sys/class/scsi_host/hostX/em_message_supported
+Date:          Oct, 2009
+KernelVersion: v2.6.39
+Contact:       linux-...@vger.kernel.org
+Description:
+               (RO) Displays supported enclosure management message types.
-- 
2.16.1

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