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>

1 files changed, 89 insertions, 0 deletions

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.