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SubjectRe: [PATCH v3 0/3] thermal: introduce by-name softlink
On Wed, Dec 11, 2019 at 12:54 AM Greg Kroah-Hartman
<> wrote:
> On Tue, Dec 10, 2019 at 09:54:11PM +0100, Daniel Lezcano wrote:
> > On 10/12/2019 21:01, Wei Wang wrote:
> > > On Tue, Dec 10, 2019 at 6:36 AM Daniel Lezcano
> > > <> wrote:
> > >>
> > >> On 05/12/2019 08:19, Wei Wang wrote:
> > >>> The paths thermal_zone%d and cooling_device%d are not intuitive and the
> > >>> numbers are subject to change due to device tree change. This usually
> > >>> leads to tree traversal in userspace code.
> tree traversal is supposed to be done in userspace code :)
Yes, that can be done in userspace, but given the amount of thermal
zones we have in some mobile devices, this will bring a lot of

e.g. this is on Pixel 4 XL:
coral:/ # ls /sys/devices/virtual/thermal/
cdev-by-name cooling_device15 cooling_device22 cooling_device3
cooling_device9 thermal_zone15 thermal_zone22 thermal_zone3
thermal_zone37 thermal_zone44 thermal_zone51 thermal_zone59
thermal_zone66 thermal_zone73 thermal_zone80 thermal_zone88
cooling_device0 cooling_device16 cooling_device23 cooling_device30
thermal_zone0 thermal_zone16 thermal_zone23 thermal_zone30
thermal_zone38 thermal_zone45 thermal_zone52 thermal_zone6
thermal_zone67 thermal_zone74 thermal_zone81 thermal_zone9
cooling_device1 cooling_device17 cooling_device24 cooling_device31
thermal_zone1 thermal_zone17 thermal_zone24 thermal_zone31
thermal_zone39 thermal_zone46 thermal_zone53 thermal_zone60
thermal_zone68 thermal_zone75 thermal_zone82 tz-by-name
cooling_device10 cooling_device18 cooling_device25 cooling_device4
thermal_zone10 thermal_zone18 thermal_zone25 thermal_zone32
thermal_zone4 thermal_zone47 thermal_zone54 thermal_zone61
thermal_zone69 thermal_zone76 thermal_zone83
cooling_device11 cooling_device19 cooling_device26 cooling_device5
thermal_zone11 thermal_zone19 thermal_zone26 thermal_zone33
thermal_zone40 thermal_zone48 thermal_zone55 thermal_zone62
thermal_zone7 thermal_zone77 thermal_zone84
cooling_device12 cooling_device2 cooling_device27 cooling_device6
thermal_zone12 thermal_zone2 thermal_zone27 thermal_zone34
thermal_zone41 thermal_zone49 thermal_zone56 thermal_zone63
thermal_zone70 thermal_zone78 thermal_zone85
cooling_device13 cooling_device20 cooling_device28 cooling_device7
thermal_zone13 thermal_zone20 thermal_zone28 thermal_zone35
thermal_zone42 thermal_zone5 thermal_zone57 thermal_zone64
thermal_zone71 thermal_zone79 thermal_zone86
cooling_device14 cooling_device21 cooling_device29 cooling_device8
thermal_zone14 thermal_zone21 thermal_zone29 thermal_zone36
thermal_zone43 thermal_zone50 thermal_zone58 thermal_zone65
thermal_zone72 thermal_zone8 thermal_zone87

> But what userspace code needs to do this, and for what?
In Android, thermal daemon and thermal HAL as well as some init.rc
script would use those thermal paths for managing and monitoring
thermal. The daemon/HAL could have logic pipled in, however Android's
init.rc script would be really tricky.
On a related note, we also create /dev/block/by-name links from userspace.

> thanks,
> greg k-h

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