Commit 0a65e125 authored by Aishwarya Pant's avatar Aishwarya Pant Committed by Tejun Heo

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: default avatarAishwarya Pant <aishpant@gmail.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 8f8ca51d
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.
......@@ -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.
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