[+CC: Felipe ]

On Sat, Oct 25, 2014 at 09:28:36AM +0200, Romain Perier wrote:

Hi Johan,

If that's still possible to do these changes, I am opened to suggestions.

Before v3.18 comes out, we can always change it with a follow-up patch.

2014-10-23 11:53 GMT+02:00 Johan Hovold [off-list ref]:

quoted

[ +CC: Guenter, Lee, linux-pm ]

On Tue, Oct 14, 2014 at 06:31:09AM +0000, Romain Perier wrote:

quoted

Several drivers create their own devicetree property when they register
poweroff capabilities. This is for example the case for mfd, regulator
or power drivers which define "vendor,system-power-controller" property.
This patch adds support for a standard property "poweroff-source"

Shouldn't this property really be called "power-off-source" or even
"power-off-controller"?

The power-off handler call-chain infrastructure is about to be merged
and will be using power[-_ ]off (i.e. not "poweroff") consistently (at
least in its interface).

"poweroff" or "power-off", I don't care. If people prefer "power-off",
choose this name :)

Let's try to stick to power off (and power_off) then.

quoted

Furthermore, isn't "controller" as in "power-off-controller" more
appropriate than "source" in this case? We have wake-up sources, which
might appear analogous, but that really isn't the same thing.

As I said, the idea with "power-off-source" (or "poweroff-source",
that's not the point here) is to mark the device as able to poweroff
the system, like "wakeup-source" which marks the device as able to
wakeup the system.
This is why I chose this name, because it is quite similar to wakeup
property except that it is for handling power, so it did make sense to
me.

The question is: what is the advantage of the suffix "controller"
compared to "source" ?

Yeah, I figured you had been inspired by the "wakeup-source" property.

The problem is that "source" tends to be used for inputs, for example,
wake-up source, interrupt source, entropy source, etc. Something that is
outside of the control of the OS. Contrary to for instance an output
which turns the system-power off.

quoted

I now this has already been merged to the regulator tree, but there's
still still time to fix this.

quoted

which marks the device as able to shutdown the system.

Signed-off-by: Romain Perier <romain.perier@gmail.com>
---
 include/linux/of.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/include/linux/of.h b/include/linux/of.h
index 6545e7a..27b3ba1 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h

@@ -866,4 +866,15 @@ static inline int of_changeset_update_property(struct of_changeset *ocs,
 /* CONFIG_OF_RESOLVE api */
 extern int of_resolve_phandles(struct device_node *tree);

+/**
+ * of_system_has_poweroff_source - Tells if poweroff-source is found for device_node
+ * @np: Pointer to the given device_node
+ *
+ * return true if present false otherwise
+ */
+static inline bool of_system_has_poweroff_source(const struct device_node *np)

Why "system_has"? Shouldn't this be of_is_power_off_source (controller)?

Note that the current custom vendor properties contain "system-" as prefix ;)

Yes, but you dropped it. ;)

And it's not the system that has the property (e.g. "poweroff-source"),
it's the node (or the device it describes).
 

we have several possibilities:
- of_system_has_power_off_source()
- of_has_power_off_source()

We should either to use "has" or "is" as prefix because that's a
predicate function.
I would prefer "has" since it refers to a property inside a node :
this node "has" the corresponding property, so "is" is not a good
candidate.

The boolean property in question describes a feature of the node
(device). Say the feature would be redness and call the property "red".
You would then generally ask whether the node *is red*, rather than
whether it has (the property) red (or has redness).

I'm actually inclined to just sticking to the current name
"system-power-controller" and just drop the vendor prefixes. Perhaps
your helper function can be used to parse both versions (i.e. with or
without a vendor prefix) as we will still need to support both.

I suggest you call that helper function

	of_is_system_power_controller(node)

or alternatively

	of_is_power_off_controller(node)

if that property name is preferred.

Note also that in at least one case (rtc-omap, patches in mm, see [1])
the property describes that the RTC is used to control an external PMIC,
which both allows us to power off the system *and* power back on again
on subsequent RTC alarms. This seems to suggest that the more generic
"system-power-controller" property name should be preferred.

Thanks,
Johan

[1] https://lkml.org/lkml/2014/10/21/631