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Re: [PATCH v2 1/2] dt-bindings: leds: gpio: Add optional retain-state-shutdown property

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On Mon, Aug 28, 2017 at 09:47:10AM +0930, Andrew Jeffery wrote:
> On Baseboard Management Controller (BMC) systems it's sometimes
> necessary for a LED to retain its state across a BMC reset (which is
> independent of the host system state). Add a devicetree property to
> describe this behaviour. The property would typically be used in
> conjunction with 'default-state = "keep"'.

A bit quick on the applying of this...

I don't understand how this works. The BMC usecase is interesting but 
that's fairly irrelevant to the binding. How do you know the GPIO state 
thru a reset? You're doing a core reset, but not reseting the GPIO 
controller?

When you use 'default-state = "keep"' but not this property? Seems like 
the same thing to me. Presumably the bootloader would just distinguish 
between a warm and cold reset to decide whether to re-init the state.

Finally, if we do have this property, why is it GPIO specific. You could 
just as easily have a LED controller IC and want to do the same thing.

Rob

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[PATCH v2 0/2] leds: gpio: Allow retaining state on shutdown Andrew Jeffery <andrew@aj.id.au> - 2017-08-28 02:20 +0200
  [PATCH v2 2/2] leds: gpio: Allow LED to retain state at shutdown Andrew Jeffery <andrew@aj.id.au> - 2017-08-28 02:20 +0200
  [PATCH v2 1/2] dt-bindings: leds: gpio: Add optional retain-state-shutdown property Andrew Jeffery <andrew@aj.id.au> - 2017-08-28 02:20 +0200
    Re: [PATCH v2 1/2] dt-bindings: leds: gpio: Add optional  retain-state-shutdown property Pavel Machek <pavel@ucw.cz> - 2017-08-28 12:30 +0200
      Re: [PATCH v2 1/2] dt-bindings: leds: gpio: Add optional  retain-state-shutdown property Brandon Wyman <bjwyman@gmail.com> - 2017-08-28 23:20 +0200
        Re: [PATCH v2 1/2] dt-bindings: leds: gpio: Add optional  retain-state-shutdown property Jacek Anaszewski <jacek.anaszewski@gmail.com> - 2017-08-29 21:20 +0200
    Re: [PATCH v2 1/2] dt-bindings: leds: gpio: Add optional  retain-state-shutdown property Rob Herring <robh@kernel.org> - 2017-08-31 23:30 +0200
      Re: [PATCH v2 1/2] dt-bindings: leds: gpio: Add optional  retain-state-shutdown property Andrew Jeffery <andrew@aj.id.au> - 2017-09-01 01:10 +0200
        Re: [PATCH v2 1/2] dt-bindings: leds: gpio: Add optional  retain-state-shutdown property Jacek Anaszewski <jacek.anaszewski@gmail.com> - 2017-09-05 21:20 +0200
  Re: [PATCH v2 0/2] leds: gpio: Allow retaining state on shutdown Jacek Anaszewski <jacek.anaszewski@gmail.com> - 2017-08-28 22:30 +0200

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