linux-kernel - Re: [GIT PULL] power_supply: add power supply scope

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Date:	Fri, 09 Dec 2011 12:36:23 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Daniel Nicoletti <dantti12@...il.com>
CC:	Anton Vorontsov <cbouatmailru@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Richard Hughes <hughsient@...il.com>,
	linux-input@...r.kernel.org, Jiri Kosina <jkosina@...e.cz>,
	vojtech@....cz, Przemo Firszt <przemo@...szt.eu>,
	Richard Hughes <richard@...hsie.com>
Subject: Re: [GIT PULL] power_supply: add power supply scope

On 12/09/2011 12:00 PM, Daniel Nicoletti wrote:
>>>> diff --git a/drivers/power/power_supply_sysfs.c b/drivers/power/power_supply_sysfs.c
>>>> index e15d4c9..21178eb 100644
>>>> --- a/drivers/power/power_supply_sysfs.c
>>>> +++ b/drivers/power/power_supply_sysfs.c
>>>> @@ -63,6 +63,9 @@ static ssize_t power_supply_show_property(struct device *dev,
>>>>      static char *capacity_level_text[] = {
>>>>              "Unknown", "Critical", "Low", "Normal", "High", "Full"
>>>>      };
>>>> +    static char *scope_text[] = {
>>>> +            "Unknown", "System", "Device"
>>>> +    };
>>>>      ssize_t ret = 0;
>>>>      struct power_supply *psy = dev_get_drvdata(dev);
>>>>      const ptrdiff_t off = attr - power_supply_attrs;
>>>> @@ -95,6 +98,8 @@ static ssize_t power_supply_show_property(struct device *dev,
>>>>              return sprintf(buf, "%s\n", capacity_level_text[value.intval]);
>>>>      else if (off == POWER_SUPPLY_PROP_TYPE)
>>>>              return sprintf(buf, "%s\n", type_text[value.intval]);
>>>> +    else if (off == POWER_SUPPLY_PROP_SCOPE)
>>>> +            return sprintf(buf, "%s\n", scope_text[value.intval]);
>>> Should we really handle the PROP_SCOPE as a dynamic property?
>>> Maybe do it similar to PROP_TYPE, so that drivers will only need to
>>> specity the scope during registration, and not bother w/ handling
>>> it in theirs get_property() callbacks?
>> I don't really know.  I guess its possible in theory that a device could
>> change scope on the fly if its power was re-routed.  But then, the type
>> can change too (if, for example, a UPS switched between AC and battery
>> power, or a HID device switching between corded USB power or cordless
>> battery power), so I'm not really sure what the rationale is either
>> way.  (I guess you model power supplies switching type as having
>> multiple power supplies which turn themselves on and offline?)
> But isn't the scope about powering or not the system? If so even if
> the device is now using AC it will not be powering the computer.
>

Sure.  I was just commenting on the similarity between scope and type
with respect to whether they're immutable properties of a power supply
or things that can change over time.

    J
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