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>
This commit is contained in:
Aishwarya Pant
Tejun Heo
parent
8f8ca51dbb
commit
0a65e12515
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@ -0,0 +1,58 @@
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What: /sys/block/*/device/sw_activity
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Date: Jun, 2008
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KernelVersion: v2.6.27
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Contact: linux-ide@vger.kernel.org
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Description:
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(RW) Used by drivers which support software controlled activity
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LEDs.
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It has the following valid values:
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0 OFF - the LED is not activated on activity
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1 BLINK_ON - the LED blinks on every 10ms when activity is
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detected.
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2 BLINK_OFF - the LED is on when idle, and blinks off
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every 10ms when activity is detected.
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Note that the user must turn sw_activity OFF it they wish to
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control the activity LED via the em_message file.
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What: /sys/block/*/device/unload_heads
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Date: Sep, 2008
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KernelVersion: v2.6.28
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Contact: linux-ide@vger.kernel.org
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Description:
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(RW) Hard disk shock protection
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Writing an integer value to this file will take the heads of the
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respective drive off the platter and block all I/O operations
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for the specified number of milliseconds.
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- If the device does not support the unload heads feature,
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access is denied with -EOPNOTSUPP.
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- The maximal value accepted for a timeout is 30000
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milliseconds.
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- A previously set timeout can be cancelled and disk can resume
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normal operation immediately by specifying a timeout of 0.
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- Some hard drives only comply with an earlier version of the
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ATA standard, but support the unload feature nonetheless.
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There is no safe way Linux can detect these devices, so this
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is not enabled by default. If it is known that your device
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does support the unload feature, then you can tell the kernel
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to enable it by writing -1. It can be disabled again by
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writing -2.
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- Values below -2 are rejected with -EINVAL
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For more information, see
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Documentation/laptops/disk-shock-protection.txt
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What: /sys/block/*/device/ncq_prio_enable
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Date: Oct, 2016
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KernelVersion: v4.10
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Contact: linux-ide@vger.kernel.org
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Description:
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(RW) Write to the file to turn on or off the SATA ncq (native
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command queueing) support. By default this feature is turned
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off.
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@ -27,3 +27,92 @@ Description: This file contains the current status of the "SSD Smart Path"
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the direct i/o path to physical devices. This setting is
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controller wide, affecting all configured logical drives on the
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controller. This file is readable and writable.
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What: /sys/class/scsi_host/hostX/link_power_management_policy
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Date: Oct, 2007
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KernelVersion: v2.6.24
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Contact: linux-ide@vger.kernel.org
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Description:
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(RW) This parameter allows the user to read and set the link
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(interface) power management.
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There are four possible options:
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min_power: Tell the controller to try to make the link use the
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least possible power when possible. This may sacrifice some
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performance due to increased latency when coming out of lower
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power states.
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max_performance: Generally, this means no power management.
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Tell the controller to have performance be a priority over power
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management.
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medium_power: Tell the controller to enter a lower power state
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when possible, but do not enter the lowest power state, thus
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improving latency over min_power setting.
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med_power_with_dipm: Identical to the existing medium_power
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setting except that it enables dipm (device initiated power
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management) on top, which makes it match the Windows IRST (Intel
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Rapid Storage Technology) driver settings. This setting is also
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close to min_power, except that:
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a) It does not use host-initiated slumber mode, but it does
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allow device-initiated slumber
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b) It does not enable low power device sleep mode (DevSlp).
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What: /sys/class/scsi_host/hostX/em_message
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What: /sys/class/scsi_host/hostX/em_message_type
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Date: Jun, 2008
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KernelVersion: v2.6.27
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Contact: linux-ide@vger.kernel.org
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Description:
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em_message: (RW) Enclosure management support. For the LED
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protocol, writes and reads correspond to the LED message format
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as defined in the AHCI spec.
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The user must turn sw_activity (under /sys/block/*/device/) OFF
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it they wish to control the activity LED via the em_message
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file.
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em_message_type: (RO) Displays the current enclosure management
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protocol that is being used by the driver (for eg. LED, SAF-TE,
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SES-2, SGPIO etc).
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What: /sys/class/scsi_host/hostX/ahci_port_cmd
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What: /sys/class/scsi_host/hostX/ahci_host_caps
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What: /sys/class/scsi_host/hostX/ahci_host_cap2
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Date: Mar, 2010
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KernelVersion: v2.6.35
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Contact: linux-ide@vger.kernel.org
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Description:
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[to be documented]
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What: /sys/class/scsi_host/hostX/ahci_host_version
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Date: Mar, 2010
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KernelVersion: v2.6.35
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Contact: linux-ide@vger.kernel.org
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Description:
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(RO) Display the version of the AHCI spec implemented by the
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host.
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What: /sys/class/scsi_host/hostX/em_buffer
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Date: Apr, 2010
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KernelVersion: v2.6.35
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Contact: linux-ide@vger.kernel.org
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Description:
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(RW) Allows access to AHCI EM (enclosure management) buffer
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directly if the host supports EM.
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For eg. the AHCI driver supports SGPIO EM messages but the
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SATA/AHCI specs do not define the SGPIO message format of the EM
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buffer. Different hardware(HW) vendors may have different
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definitions. With the em_buffer attribute, this issue can be
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solved by allowing HW vendors to provide userland drivers and
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tools for their SGPIO initiators.
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What: /sys/class/scsi_host/hostX/em_message_supported
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Date: Oct, 2009
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KernelVersion: v2.6.39
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Contact: linux-ide@vger.kernel.org
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Description:
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(RO) Displays supported enclosure management message types.
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