Re: [PATCH v5 3/3] leds: Add control of the voltage/current regulator to the LED core

[Jean-Jacques Hiblot]

On 13/10/2019 14:09, Pavel Machek wrote:
> Hi!
>
> > I must say I'm not a big fan of this change.
> > It adds a bunch of code to the LED core and gives small
> > functionality in a reward. It may also influence maximum
> > software blinking rate, so I'd rather avoid calling
> > regulator_enable/disable when timer trigger is set.
> >
> > It will of course require more code.
> >
> > Since AFAIR Pavel was original proponent of this change then
> > I'd like to see his opinion before we move on to discussing
> > possible improvements to this patch.
> Was I?
>
> Okay, this series looks quite confusing to me. First, 1/3 looks
> "interesting" (would have to analyze it way more).
>
> Second, 3/3... So we have a LED driver _and_ a regulator? So yes, the
> chip driving a LED is usually ... voltage/current regulator. What is
> second regulator doing there? Is that a common setup?

This is quite common with current-sink LED drivers.

The setup looks like this:

+-----------+
|           |
| Regulator |
|           +------------------------+
|           |                        |
+-----------+                      __|__
                                   \   /
         +---------------------+    \ / led
         |                     |     V
         |    Led Driver       |   --+--
         |                     |     |
         |                     |     |
         |                +----------+
         |              \      |
         |               \     |
         |                +    |
         |                |    |
         +---------------------+
                          |
                       +--+--+
                       ///////


Only the regulator usually does not supply only one LED.

JJ


> Best regards,
> 								Pavel
>