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/admin-guide/laptops/disk-shock-protection.rst


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.
