linux-kernel - Re: [RFC PATCH 0/5] device property: Introducing software nodes

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Date:   Tue, 16 Oct 2018 17:46:22 +0300
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: [RFC PATCH 0/5] device property: Introducing software nodes

On Tue, Oct 16, 2018 at 05:35:50PM +0300, Andy Shevchenko wrote:
> On Fri, Oct 12, 2018 at 2:41 PM Heikki Krogerus
> <heikki.krogerus@...ux.intel.com> wrote:
> >
> > Hi guys,
> >
> > To continue the discussion started by Dmitry [1], this is my proposal
> > that I mentioned in my last mail. In short, the idea is that instead
> > of trying to extend the support for the currently used struct
> > property_set, I'm proposing that we introduce a completely new,
> > independent type of fwnode, and replace the struct property_set with
> > it. I'm calling the type "software node" here.
> >
> > The reason for a complete separation of the software nodes from the
> > generic property handling code is the need to be able to create the
> > nodes independently from the devices that they are bind to.
> >
> > The way this works is that every node that is created will have a
> > kobject registered. That will take care the ref counting for us, and
> > also allow us to for example display the properties in sysfs.
> >
> > There are a few more details in patch 3/5 about the software nodes in
> > the commit message.
> >
> > [1] https://lkml.org/lkml/2018/9/17/1067
> 
> In private discussion I brought a concern that we exposed properties
> as a part of ABI, but at the same time we have not strict rules which
> might lead to ambiguous reading, e.g. there is no type exported and
> thus no possibility to tell what kind of property it is.
> 
> Examples:
> 1. 0x1 and 0x1 ??? are they of the same type?
> 2. 0x1 ??? is it an array or single value?
> 3. 0x12345678 ??? is it string or hex?
> 4. 25 ??? is it hex or decimal?
> 
> Until these will not be solved, better to not to expose properties to userspace.

I agree. I'll drop that part from my final version.


Thanks Andy,

-- 
heikki