On 02/02/2017 09:44 PM, Jacek Anaszewski wrote:
On 02/01/2017 10:55 PM, Rafał Miłecki wrote:
On 02/01/2017 10:26 PM, Jacek Anaszewski wrote:
On 02/01/2017 04:56 PM, Rafał Miłecki wrote:
On 01/31/2017 10:34 PM, Jacek Anaszewski wrote:
On 01/31/2017 05:11 PM, Rafał Miłecki wrote:
Thanks a lot Jacek for this explanation (and sorry but I needed a
bit of
time to
think about this). I can finally see your point, I think we're on the
same page
now.
I think that for all this time I was thinking from the pure DT
perspective. If
you ignore fact that Linux has multiple LED trigger drivers, then
"led-triggers"
may not sound that bad.
After reading your description however I can see this property can be
misleading
as Linux people may think "drivers" when seeing "triggers".
I still think this is a useful property and I hope we can still find a
way to
name it in a sane way: to be nice from DT PoV and march Linux LEDs
subsystem.
I also see the need for this property.
I think we should still work on some generic property (without linux,
prefix) as
this seems to be something generic, not really specific to Linux
implementation.
Specifying relation between LED and devices is something than AFAICS
can be
reused by other systems as well.
So my suggestion is to try some new name & leave linux,default-trigger
to allow
specifying one single trigger driver as required by current Linux
implementation.
What do you think about this?
There are few suggestions to came to my mind:
"trigger-sources"
"trigger-devices"
"led-trigger-devices"
"led-related-devices"
"led-event-devices"
trigger-devices would work in this specific use case,
where we can give phandles to usb ports. Nonetheless, we
have also other kernel based events serving as trigger
sources - e.g. timer.
In this case I'd go for trigger-sources, but we'd need
to have some generic way of defining the source like timer.
I'd leave timer for later discussion but I'm glad you brought this
problem.
Maybe we could discuss this on another example that is more supported
like
GPIOs?
We know this property allows specifying USB ports and we want it to
support
mixing various sources. So a very simple sample case seems to be using
it for
specifying GPIO as trigger source.
Is this possible to mix various entries in a list assigned to single
property?
Let's say:
trigger-sources =
<&ohci_port1>,
<&ehci_port1>,
<&gpio 1 GPIO_ACTIVE_HIGH>;
According to my knowledge all elements in the list are elements
of one array, no matter if they are comma separated or space separated
in "<>" brackets. DT maintainer would have to confirm that though.
This matches my knowledge as well.
Having that, we would be limited to a list of fixed size
tuples IMHO.
That sounds OK. Now I spent some time thinking about this I think it can work.
First of all we may need something like #sources-cells to extend our property
in the future.
Secondly it should be possible to detect type of phandle node by trying things
one by one. We should be e.g. able to check is phandle is for GPIO by trying
of_find_gpiochip_by_xlate.
Is this possible to support this? If so, which function I can use to
detect
what is pointed by a phandle?
I'm not that familiar with DT and I'm not sure how to handle this.
I wonder if this is correct way to go. Maybe we should think of
creating entirely new trigger mechanism that would allow for having
multiple active triggers at a time.
I'm OK with reworking Linux's triggers if it need be. I think we should
agree
on binding(s) first though.
I was thinking of creating entirely new mechanism (new sysfs file),
as we can't break existing users.
Agree.
Of course trigger-sources would be still useful for defining
a list of devices of the same type like in case of usbport trigger.
Nonetheless, I have a problem with this property being a part of
LED class device DT bindings. Triggers are not tightly coupled with
LED class devices, but trigger-sources being a list of usb ports
would be applicable only to usbport trigger. What if there was
another combo trigger e.g. for reporting activity on mulitple GPIOs?
That was exactly my point with above trigger-sources example including 2
USB
ports & GPIO.
How usbport trigger would make use use of information about GPIO?
Does it mean that in this approach triggers would arbitrarily choose
trigger-sources applicable for them?
It wouldn't. It would simply ignore it.
We could modify ledtrig-gpio.c however to support this new property
(ex-"led-triggers") and make use of specified GPIO(s). Of course ledtrig-gpio
would ignore specified USB ports. One type per LED trigger driver.
Should we have separate list of trigger sources per any possible
existing trigger type? Aren't we going to far from pure hardware
description the Device Tree was initially predestined to?
That would simplify things, but it gets us back to *multiple* properties
like
led-usb-triggers (or led-usb-trigger-sources)
led-pci-triggers (or led-pci-trigger-sources)
led-gpio-triggers (or led-gpio-trigger-sources)
etc.
Right, I was rather skeptical in my question - I don't like this
solution too.
