On 03/08/2023 21:58, Rafael J. Wysocki wrote:
On Thu, Aug 3, 2023 at 6:20 PM Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> wrote:
On 03/08/2023 16:15, Rafael J. Wysocki wrote:
On Thu, Aug 3, 2023 at 3:06 PM Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> wrote:
On 02/08/2023 18:48, Rafael J. Wysocki wrote:
[ ... ]
Let me check if I can do something on top of your series to move it in
the ACPI driver.
It doesn't need to be on top of my series, so if you have an idea,
please just let me know what it is.
It can't be entirely in the ACPI driver AFAICS, though, because
trips[i] need to be modified on updates and they belong to the core.
Hence, the driver needs some help from the core to get to them. It
can be something like "this is my trip tag and please give me the
address of the trip matching it" or similar, but it is needed, because
the driver has to assume that the trip indices used by it initially
may change.
May be I'm missing something but driver_ref does not seems to be used
except when assigning it, no?
It is used on the other side. That is, the value assigned to the trip
field in it is accessed via trip_ref in the driver.
The idea is that the driver puts a pointer to its local struct
thermal_trip_ref into a struct thermal_trip and the core stores the
address of that struct thermal_trip in there, which allows the driver
to access the struct thermal_trip via its local struct
thermal_trip_ref going forward.
Admittedly, this is somewhat convoluted.
I have an alternative approach in the works, just for illustration
purposes if nothing else, but I have encountered a problem that I
would like to ask you about.
Namely, zone disabling is not particularly useful for preventing the
zone from being used while the trips are updated, because it has side
effects. First, it triggers __thermal_zone_device_update() and a
netlink message every time the mode changes, which can be kind of
overcome.
Right
But second, if the mode is "disabled", it does not actually
prevent things like __thermal_zone_get_trip() from running and the
zone lock is the only thing that can be used for that AFAICS.
>
So by "disabling" a thermal zone, did you mean changing its mode to
"disabled" or something else?
Yes, that is what I meant.
May be the initial proposal by updating the thermal trips pointer can
solve that [1]
No, it can't. An existing trips[] table cannot be replaced with a new
one with different trip indices, because those indices are already in
use. And if the indices are the same, there's no reason to replace
trips.
IMO we can assume the trip point changes are very rare (if any), so
rebuilding a new trip array and update the thermal zone with the pointer
may solve the situation.
The routine does a copy of the trips array, so it can reorder it without
impacting the array passed as a parameter. And it can take the lock.
The driver can take a lock as well. Forbidding drivers to use the
zone lock is an artificial limitation without technical merit IMV.
Yes, it is technically possible to take a lock from a driver. However,
from a higher perspective, we have a core framework which is
self-contained and we have a back-end which forces us to export this lock.
Even if it is possible, it is not desirable because we break the
self-containment and thus that will make future changes in the core
framework complicated because of the interactions with back-end drivers.
I'm not putting in question your changes in general but just want to
keep the direction of having the core framework and the drivers
interacting with the ops and a few high level functions where the core
framework handle the logic.
The clocksource/clockevent drivers are an example on how the time
framework and the drivers are clearly separated.
We just have to constraint the update function to invalidate arrays with
a number of trip points different from the one initially passed when
creating the thermal zone.
Alternatively, we can be smarter in the ACPI driver and update the
corresponding temperature+hysteresis trip point by using the
thermal_zone_set_trip() function.
I don't see why this would make any difference.
The function thermal_zone_set_trip() takes the lock.
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