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SubjectRe: [PATCH v5 3/3] leds: Add control of the voltage/current regulator to the LED core
On Mon, Oct 14, 2019 at 12:49:07PM +0200, Jean-Jacques Hiblot wrote:
>
> 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.

Given questions have been raised about the complexity of the change I
wondered whether, for a system with this topology, the regulator
could/should be enabled when the LED driver driver probes?


Daniel.

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