linux-kernel - Re: [PATCH V1 Resend 2/3] cpufreq: dt: Add generic platform-device creation support

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Message-ID: <56FE69E0.1080800@free.fr>
Date:	Fri, 1 Apr 2016 14:30:24 +0200
From:	Mason <slash.tmp@...e.fr>
To:	Viresh Kumar <viresh.kumar@...aro.org>,
	Arnd Bergmann <arnd@...db.de>
Cc:	linaro-kernel@...ts.linaro.org, k.kozlowski@...sung.com,
	kgene.kim@...sung.com, heiko@...ech.de, linux-pm@...r.kernel.org,
	mmcclint@...eaurora.org, xf@...k-chips.com,
	Rafael Wysocki <rjw@...ysocki.net>,
	linux-kernel@...r.kernel.org, rob.herring@...aro.org,
	Sebastian Frias <sebastian_frias@...madesigns.com>
Subject: Re: [PATCH V1 Resend 2/3] cpufreq: dt: Add generic platform-device
 creation support

On 01/04/2016 12:23, Viresh Kumar wrote:

> Cc'ing Rob and Mason.
> 
> On 30-03-16, 09:53, Arnd Bergmann wrote:
>
>> I think it should be something in the /cpus or the /opp_table hierarchy,
>> not the root of the device tree, but other than that I don't care much
>> whether it's a variation of the oppv2 compatible string or an additional
>> property in any of the nodes.
> 
> So you mean for future DT files we can have something like this:
> 
> 	cpus {
>               compatible = "operation-points-v2";
>               [...]
> 
> And the cpufreq-dt driver can match /cpus node's compatible string against
> "operating-points-v2" and create a device at runtime ?

Hmmm... I'm using the older operating-points prop in my platform's DT.
Why can't we define a new property (e.g. "enable-generic-cpufreq")
which registers the "cpufreq-dt" pseudo-device?

And platforms that manually register "cpufreq-dt" would be
automatically white-listed, even if they don't have the new
property, to maintain backward-compat?

> @Rob: Will that be acceptable to you? We are discussing (again) about how to
> probe cpufreq-dt driver automatically for platforms :)
> 
> The cpus node doesn't have any 'compatible' property today, and I will be
> required to add that in this case.

Why does it need a compatible prop?
Why isn't a bool prop enough?

Regards.