Re: [RFC] improve binding for linux,wdt-gpio

Hello Guenter,

On Thu, Jul 30, 2015 at 12:25:07AM -0700, Guenter Roeck wrote:

On 07/29/2015 11:59 PM, Uwe Kleine-König wrote:

quoted

On Wed, Jul 29, 2015 at 08:49:23AM -0700, Guenter Roeck wrote:

quoted

On 07/29/2015 12:35 AM, Uwe Kleine-König wrote:

quoted

quoted

always-running is meant to indicate that the watchdog can not be stopped
(meaning a timer has to be used to send keepalives while the watchdog
device is closed). The documentation specifically states that.

"If the watchdog timer cannot be disabled ..."

How would you express that condition without always-running or a similar
attribute ?  I am also not sure how that relates to hw_algo; I thought
those properties are orthogonal.

For hw_algo = "level" the inactive level of the gpio disables the
watchdog (and resets the counter). So always-running doesn't make sense
for this type.

That is not what is currently implemented. "level" just means that

I'm not talking (yet) about the implementation.

quoted

the watchdog is pinged using a -high-low-high- or -low-high-low-
sequence, while toggle means that the level is changed with each
ping (-low-(wait)-high-(wait)-low-(wait)-high-...).

Currently the document tells us:

hw_algo: [...]
- level: Low or high level starts counting WDT timeout, the
  opposite level disables the WDT.

So similar to the "toggle" description there is some behaviour about
being disabled in certain states implied.

It might be that you put too much emphasis on the documentation and
little or none on the code. We already established that the documentation
is less than perfect. It might make sense to clean up the documentation
first to ensure that it matches what it is actually meant to document.

I'm not sure you wrote here what you intended to write?!
 

Sure, I understand, the devicetree bindings are supposed to be
implementation independent. We all know that this is an ideal view
which often does not match reality, as the code tends to be written
first and the devicetree bindings tend to be an afterthought.

I think for drivers that work with a single type of device it works well
the other way round. But for something as generic as a gpio watchdog
that is supposed to drive several different types of devices I think
agreeing on which way to go is more time saving than to come up with an
implementation first that then needs change on feedback.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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