Re: [PATCH v2 1/2] leds: Add Intel Cherry Trail Whiskey Cove PMIC LEDs

From: Hans de Goede
Date: Mon Feb 18 2019 - 06:12:30 EST


Hi,

On 17-02-19 18:45, Pavel Machek wrote:
Hi!

I see... and yes, that would be the easiest solution.

But somehow I see "this LED is controlled by charging state" as
primary and "it shows pulses instead of staying on" as secondary
eye-candy.

This week there was another driver for charger LED.. but that one does
not do pulses. Ideally, we'd like consistent interface to the
userland.

(To make it complex, the other driver supports things like:
LED solid on -- fully charged
LED blinking slowly -- charging
LED blinking fast -- charge error
LED off -- not charging).

Something like that could be supported with my original hw_pattern
proposal where we simply encode all of this in the hw-pattern file:

tupple0: charging blinking_on_time
tupple1: charging blinking_off_time
tupple2: charging breathing_time
tupple3: manual blinking_on_time
tupple4: manual blinking_off_time
tupple5: manual breathing_time

So the userland would need to know "I'm on yoga, so 3rd tupple sets up
breathing when charging"?

Yes this is for the hw_pattern file not the regular pattern file and if I've
understood things correctly then the hw_pattern file is often (always?)
specific to the LED controller model. See e.g. :
Documentation/ABI/testing/sysfs-class-led-driver-sc27xx

Also userland is not really expected to touch this, the user himself
could touch it if he/she wants to customize things.

So for this chip you mention, we do not need the breathing time (no breathing support),
so we would get the following tupples:

tupple0: not charging blinking_on_time
tupple1: not charging blinking_off_time
tupple2: slow charging blinking_on_time
tupple3: slow charging blinking_off_time
tupple4: fast charging blinking_on_time
tupple5: fast charging blinking_off_time
tupple6: charging error blinking_on_time
tupple7: charging error blinking_off_time

Patterns and their meanings are fixed (or almost) on that driver, so
fortunately that will not be neccessary.

Ok, so back the Whiskey Cove PMIC LED controller, I think
there was some agreement to add a hw_control sysfs
attribute and simplify the hw_pattern ABI to:

tupple0: blinking_on_time
tupple1: blinking_off_time
tupple2: breathing_time

You suggested adding support for a hw_control
sysfs attribute to the core, activated by a flag.

I assume that there will then be a callback into the
driver when that file gets written. The semantics for
the Whiskey Cove PMIC LED controller are clear, but
how should the patch adding support for this to the LED core
describe the new hw_control sysfs attribute in:
Documentation/ABI/testing/sysfs-class-led ?

Or do you just want to have the basic handling in the
core and then describe the semantics in a per LED controller
way like how we do for hw_pattern, so for the
Whiskey Cove PMIC LED controller we would add a:
Documentation/ABI/testing/sysfs-class-led-cht-wc
file, which we need to do anyways for the hw_pattern file?

<snip stuff about N900>

Regards,

Hans





Where by solid on/off can be done by setting one
of the blinking times to 0.

Having hw_pattern ABIs like this where some of
the tupples only activate on certain conditions
might be better then a hardware_control sysfs
file as it offers more flexibility.

Agreed about flexibility, but I don't think it does enough to provide
hardware abstraction. It might be too much flexibility.

Also it only works with hw controlled LEDs.

With RGB LED multiple patterns per LED make a lot of sense (as there's
typically just one led.

For example on N900, we have

green: fully charged.
yellow pulsing: charging.
solid yellow: hardware feature, emergency charging.
white pulsing: happy phone, no events
blue fast pulses: message waiting

On N900, I'm handling that in userspace, but...

Best regards,
Pavel