linux-kernel - Re: [PATCH v5] Introduce support for Systems Management Driver over WMI for Dell Systems

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Date:   Thu, 1 Oct 2020 11:26:36 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     "Limonciello, Mario" <Mario.Limonciello@...l.com>,
        "mgross@...ux.intel.com" <mgross@...ux.intel.com>,
        Divya Bharathi <divya27392@...il.com>
Cc:     "dvhart@...radead.org" <dvhart@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>,
        "Bharathi, Divya" <Divya.Bharathi@...l.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        "Ksr, Prasanth" <Prasanth.Ksr@...l.com>
Subject: Re: [PATCH v5] Introduce support for Systems Management Driver over
 WMI for Dell Systems

Hi,

On 9/30/20 11:02 PM, Limonciello, Mario wrote:
>>> +		possible_values:	A file that can be read to obtain the possible
>>> +					values of the <attr>. Values are separated using
>>> +					semi-colon (``;``).
>> why not use set notation from math classes assuming intergers?  i.e.
>> (a, b)  all integers beween a and b but not including a or b (open set)
>> or
>> [a, b] all integerger betwen a and b including and b?  (closed set)
>>
>> Anyway its ambiguous if the the extremes are included in the set of possible
>> values as written.
>>
> 
> Enumeration attributes mean that there are fixed values, specifically not integers.
> Integers are in the "integer" type and explained below.
> 
> An example value that would be seen here is possible_values:
> 
> Enabled;Disabled;

That might not be the best example, because in that case arguably we
could export it as a boolean type (except that the WMI interface does
not give us boolean as an explicit / separate type).

Mark these enum attributes are really like enums in C, so we
have a fixed set of possible values which are described by
strings, since using integers for it makes no sense from a human
interaction pov. E.g. on the Lenovo X1C8 I have some attributes
have the following possible value sets:

                 Package (0x03)
                 {
                     "High",
                     "Normal",
                     "Silent"
                 },

                 Package (0x02)
                 {
                     "LCD",
                     "ExternalDisplay"
                 },

                 Package (0x02)
                 {
                     "Independent",
                     "Synchronized"
                 },

I hope this helps clarify things.

Regards,

Hans