libata: update documentation for sysfs interfaces

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 <aishpant@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

2 files changed, 147 insertions, 0 deletions

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-ide@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-ide@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-ide@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-ide@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-ide@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-ide@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-ide@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-ide@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-ide@vger.kernel.org
+Description:
+                (RO) Displays supported enclosure management message types.