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SubjectRe: [PATCH v3 0/3] thermal: introduce by-name softlink
On Wed, Dec 11, 2019 at 1:11 PM Daniel Lezcano
<daniel.lezcano@linaro.org> wrote:
>
> On 11/12/2019 21:11, Wei Wang wrote:
> > On Wed, Dec 11, 2019 at 12:54 AM Greg Kroah-Hartman
> > <gregkh@linuxfoundation.org> 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
> >>>> <daniel.lezcano@linaro.org> 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
> > convenience.
>
> But usually all these thermal zones are fixed and building the name<->tz
> association is just a question of a few lines of code from userspace,
> no? What would be the benefit of adding more ABI?


code reuse as tz mapping is per device tree setup and we try to use
the same _type_ in thermal zone in shared client code for Android
thermal API.

>
> If there is a thermal zone change, then a notification can be used, so
> the userspace code rebuild the name<->tz, no?


Assuming you meant for type<->tz, this mapping won't change in runtime
in our case (not unloading things), but it could be changed due to
device tree change, e.g. adding/removing thermal zones.


>
> > 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!
> > -Wei
> >>
> >> thanks,
> >>
> >> greg k-h
>
>
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>
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