1.. SPDX-License-Identifier: GPL-2.0
2
3Kernel driver drivetemp
4=======================
5
6
7References
8----------
9
10ANS T13/1699-D
11Information technology - AT Attachment 8 - ATA/ATAPI Command Set (ATA8-ACS)
12
13ANS Project T10/BSR INCITS 513
14Information technology - SCSI Primary Commands - 4 (SPC-4)
15
16ANS Project INCITS 557
17Information technology - SCSI / ATA Translation - 5 (SAT-5)
18
19
20Description
21-----------
22
23This driver supports reporting the temperature of disk and solid state
24drives with temperature sensors.
25
26If supported, it uses the ATA SCT Command Transport feature to read
27the current drive temperature and, if available, temperature limits
28as well as historic minimum and maximum temperatures. If SCT Command
29Transport is not supported, the driver uses SMART attributes to read
30the drive temperature.
31
32
33Usage Note
34----------
35
36Reading the drive temperature may reset the spin down timer on some drives.
37This has been observed with WD120EFAX drives, but may be seen with other
38drives as well. The same behavior is observed if the 'hdtemp' or 'smartd'
39tools are used to access the drive.
40With the WD120EFAX drive, reading the drive temperature using the drivetemp
41driver is still possible _after_ it transitioned to standby mode, and
42reading the drive temperature in this mode will not cause the drive to
43change its mode (meaning the drive will not spin up). It is unknown if other
44drives experience similar behavior.
45
46A known workaround for WD120EFAX drives is to read the drive temperature at
47intervals larger than twice the spin-down time. Otherwise affected drives
48will never spin down.
49
50
51Sysfs entries
52-------------
53
54Only the temp1_input attribute is always available. Other attributes are
55available only if reported by the drive. All temperatures are reported in
56milli-degrees Celsius.
57
58=======================	=====================================================
59temp1_input		Current drive temperature
60temp1_lcrit		Minimum temperature limit. Operating the device below
61			this temperature may cause physical damage to the
62			device.
63temp1_min		Minimum recommended continuous operating limit
64temp1_max		Maximum recommended continuous operating temperature
65temp1_crit		Maximum temperature limit. Operating the device above
66			this temperature may cause physical damage to the
67			device.
68temp1_lowest		Minimum temperature seen this power cycle
69temp1_highest		Maximum temperature seen this power cycle
70=======================	=====================================================
71