linux-kernel - Re: [PATCH 0/1] Compact interface for Device-Tree

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Message-Id: <20141104155329.A23A5C423D0@trevor.secretlab.ca>
Date:	Tue, 04 Nov 2014 15:53:29 +0000
From:	Grant Likely <grant.likely@...aro.org>
To:	Arnd Bergmann <arnd@...db.de>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Rob Herring <robherring2@...il.com>,
	Gilad Avidov <gavidov@...eaurora.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Sagar Dharia <sdharia@...eaurora.org>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	David Woodhouse <dwmw2@...radead.org>
Subject: Re: [PATCH 0/1] Compact interface for Device-Tree

On Mon, 03 Nov 2014 16:06:03 +0100
, Arnd Bergmann <arnd@...db.de>
 wrote:
> On Friday 31 October 2014 23:53:28 Rafael J. Wysocki wrote:
> > On Saturday, November 01, 2014 05:13:45 AM Rob Herring wrote:
> > > On Fri, Oct 31, 2014 at 6:59 AM, Gilad Avidov <gavidov@...eaurora.org> wrote:
> > > >
> > > > Device-Tree compact API
> > > > ------------------------
> > > >
> > > > Common code seen in driver’s probe reads device tree values and handling
> > > > erroneous return codes from all those of_property_read_xxx()  APIs. This
> > > > common code is factored out by the of_property_map module which allows
> > > > driver’s probe to replace that (often lengthy) code with a concise table:
> > > >
> > > > struct of_prop_map map[] = {
> > > >     {"i2c",            &dev->id,        OF_REQ,  OF_ID,  -1},
> > > >     {"qcom,clk-freq-out",    &dev->clk_freq_out,    OF_REQ,  OF_U32,  0},
> > > >     {"qcom,clk-freq-in",    &dev->clk_freq_in,    OF_REQ,  OF_U32,  0},
> > > >     {"qcom,disable-dma",    &dev->disable_dma,    OF_OPT,  OF_BOOL, 0},
> > > >     {"qcom,master-id",    &dev->mstr_id,        OF_SGST, OF_U32,  0},
> > > >     {NULL,            NULL,            0,       0,       0},
> > > > };
> > > >
> > > > Then call populate to read the values into the device’s variables:
> > > >
> > > > ret = of_prop_populate(dev, dev->of_node, map);
> > > 
> > > Interesting idea. The main concern I have with this is there has been
> > > on-going discussions about how to generalize property handling across
> > > DT and ACPI to make drivers more agnostic, so I'm copying a few folks
> > > involved in that. That may be a bit orthogonal to what this is doing,
> > > but we may want some coordination here.
> > 
> > Agreed.
> > 
> > We actually have a patchset adding a unified device property API in 
> > linux-next (http://git.kernel.org/cgit/linux/kernel/git/rafael/linux-pm.git/log/?h=device-properties)
> > and I'd prefer to see the "compactization" to happen at that level, if possible,
> > rather that for of_ only.
> 
> Agreed, this should definitely use the new generalized API.
> I have prototyped a similar concept last year, which actually went much
> further and also abstracted high-level properties such as interrupts,
> gpios, pwm, dma-engine, etc. I still think we should do something
> like that, but I've never had the time to follow up and nobody else
> picked up my work from back then.
> 
> Would others like to see that?

Absolutely. I also tried to do the same thing and didn't get very far.
And, yes, it should be done at the level of the device properties API.

g.

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