From: Pantelis Antoniou <panto@antoniou-consulting.com>
To: Grant Likely <grant.likely@secretlab.ca>
Cc: Mitch Bradley <wmb@firmworks.com>,
Stephen Warren <swarren@wwwdotorg.org>,
Kevin Hilman <khilman@ti.com>, Matt Porter <mporter@ti.com>,
Koen Kooi <koen@dominion.thruhere.net>,
linux-kernel <linux-kernel@vger.kernel.org>,
Felipe Balbi <balbi@ti.com>, Deepak Saxena <dsaxena@linaro.org>,
Scott Wood <scottwood@freescale.com>,
Russ Dill <Russ.Dill@ti.com>,
linux-omap@vger.kernel.org, devicetree-discuss@lists.ozlabs.org
Subject: Re: [RFC] Device Tree Overlays Proposal (Was Re: capebus moving omap_devices to mach-omap2)
Date: Mon, 12 Nov 2012 13:29:28 +0200 [thread overview]
Message-ID: <53E5CE97-0CA5-416A-BC57-01B6A7C87973@antoniou-consulting.com> (raw)
In-Reply-To: <CACxGe6vTJHvZwZ383DE5-k+ksv1nGeuLynADuQC+D2eySj7gWQ@mail.gmail.com>
Hi Grant,
On Nov 9, 2012, at 7:02 PM, Grant Likely wrote:
> On Wed, Nov 7, 2012 at 12:54 AM, Mitch Bradley <wmb@firmworks.com> wrote:
>> On 11/6/2012 12:37 PM, Stephen Warren wrote:
>>> This proposal is very oriented at an overlay-based approach. I'm not
>>> totally convinced that a pure overlay approach (as in how dtc does
>>> overlayed DT nodes) will be flexible enough, but would love to be
>>> persuaded. Again see below.
>>
>>
>> An overlay approach will not be powerful enough to solve the sorts of
>> problems that occur when a product goes into full production, becomes a
>> family, and starts to evolve. Issues like second-source parts that
>> aren't quite compatible and need to be detected and reported,
>> board-stuff options for different customer profiles, speed grades of
>> parts that aren't properly probeable but instead need to be identified
>> by some subterfuge, the list of tedious issues goes on and on.
>>
>> It's nice to pretend that the world fits into a few coherent simple
>> use cases, but 30 years of experience shipping computer product families
>> proves otherwise. You need a programming language to solve the full
>> set of problems - which I why the device tree is designed so it can
>> be generated and modified by a program.
>
> I'm not going to argue with that. There is nothing saying that the
> overlay wouldn't be generated or applied by a script. However, I do
> strongly think that the data model needs to be independent of any tool
> or execution environment used to manipulate it. I certainly am not
> interested in encoding scripts or bytecode into the tree - the
> opposite of the approach used by ACPI which must execute AML to even
> retrieve the device tree. I like the overlay approach because it is
> conceptually straightforward and provides a working model of how
> changes could be made from userspace while still being usable by
> firmware.
>
> An alternate approach from userspace would be to use a live virtual
> filesystem to manipulate the device tree, though that approach only
> applies to Linux userspace. Firmware would still need its own
> approach.
>
> g.
I completely agree here.
I certainly wouldn't want to introduce any kind of bytecode or a
programming model for manipulating DT. I know OF has a full blown
forth interpreter, but that's not what modern DT should be (IMHO).
Having DT provide such a programming model will preclude a number
of users of accessing it, and on top of that, complexity will
increase considerably.
When faced with a new problem, vendors will just code a workaround,
never bothering fixing it properly.
In a nutshell, let's not turn DT into ACPI, please.
Regards
-- Pantelis
next prev parent reply other threads:[~2012-11-12 11:29 UTC|newest]
Thread overview: 99+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-05 20:40 [RFC] Device Tree Overlays Proposal (Was Re: capebus moving omap_devices to mach-omap2) Grant Likely
2012-11-05 21:40 ` Tabi Timur-B04825
2012-11-05 23:22 ` Tony Lindgren
2012-11-09 12:06 ` Grant Likely
2012-11-06 0:07 ` Grant Likely
2012-11-06 10:31 ` Pantelis Antoniou
2012-11-07 22:35 ` Ryan Mallon
2012-11-08 13:28 ` Koen Kooi
2012-11-08 14:09 ` Timur Tabi
2012-11-08 17:00 ` Mitch Bradley
2012-11-06 10:30 ` Pantelis Antoniou
2012-11-06 11:14 ` Grant Likely
2012-11-06 18:35 ` Tony Lindgren
2012-11-06 19:29 ` Russ Dill
2012-11-06 19:41 ` Pantelis Antoniou
2012-11-06 22:17 ` Stephen Warren
2012-11-06 19:34 ` Pantelis Antoniou
2012-11-06 20:45 ` Grant Likely
2012-11-06 20:50 ` Grant Likely
2012-11-07 8:06 ` Pantelis Antoniou
2012-11-07 15:33 ` Alan Tull
2012-11-09 17:03 ` Grant Likely
2012-11-07 8:13 ` Pantelis Antoniou
2012-11-07 10:19 ` Benoit Cousson
2012-11-07 11:02 ` Pantelis Antoniou
2012-11-07 11:12 ` Benoit Cousson
2012-11-07 11:23 ` Pantelis Antoniou
2012-11-09 20:33 ` Grant Likely
2012-11-12 11:34 ` Pantelis Antoniou
2012-11-12 13:01 ` Grant Likely
2012-11-07 17:25 ` Stephen Warren
2012-11-07 22:10 ` Pantelis Antoniou
2012-11-08 10:36 ` Cousson, Benoit
2012-11-09 5:32 ` Joel A Fernandes
2012-11-09 14:29 ` David Gibson
2012-11-10 3:15 ` Joel A Fernandes
2012-11-09 21:22 ` Grant Likely
2012-11-12 11:47 ` Pantelis Antoniou
2012-11-13 3:59 ` Joel A Fernandes
2012-11-09 22:59 ` Stephen Warren
[not found] ` <-4237940489086529028@unknownmsgid>
[not found] ` <559B8433-67C3-4A1A-A5D6-859907655176@antoniou-consulting.com>
2012-11-10 3:36 ` Joel A Fernandes
2012-11-12 12:48 ` Pantelis Antoniou
2012-11-13 2:28 ` David Gibson
2012-11-06 22:37 ` Stephen Warren
2012-11-07 0:54 ` Mitch Bradley
2012-11-09 17:02 ` Grant Likely
2012-11-12 11:29 ` Pantelis Antoniou [this message]
2012-11-07 8:47 ` Pantelis Antoniou
2012-11-07 17:18 ` Stephen Warren
2012-11-07 22:08 ` Pantelis Antoniou
2012-11-09 16:28 ` Grant Likely
2012-11-09 23:23 ` Stephen Warren
2012-11-09 23:40 ` Grant Likely
2012-11-12 10:53 ` Koen Kooi
2012-11-12 12:10 ` Pantelis Antoniou
2012-11-12 16:52 ` Stephen Warren
2012-11-13 7:25 ` David Gibson
2012-11-13 8:09 ` Pantelis Antoniou
2012-11-13 12:24 ` Grant Likely
2012-11-13 13:38 ` Pantelis Antoniou
2012-11-15 4:57 ` David Gibson
2012-11-13 17:10 ` Stephen Warren
2012-11-13 23:30 ` David Gibson
2012-11-14 0:00 ` Pantelis Antoniou
2012-11-13 16:57 ` Stephen Warren
2012-11-13 18:10 ` Mitch Bradley
2012-11-13 18:29 ` Stephen Warren
2012-11-13 19:09 ` Mitch Bradley
2012-11-13 19:11 ` Pantelis Antoniou
2012-11-17 22:27 ` Jean-Christophe PLAGNIOL-VILLARD
2012-11-20 17:09 ` Grant Likely
2012-11-11 20:47 ` Rob Landley
2012-11-12 12:50 ` Pantelis Antoniou
2012-11-12 16:54 ` Stephen Warren
2012-11-12 11:23 ` Pantelis Antoniou
2012-11-12 16:49 ` Stephen Warren
2012-11-12 17:00 ` Pantelis Antoniou
2012-11-12 17:10 ` Stephen Warren
2012-11-12 17:19 ` Pantelis Antoniou
2012-11-12 17:29 ` Stephen Warren
2012-11-12 17:38 ` Pantelis Antoniou
2012-11-12 20:16 ` Russ Dill
2012-11-12 16:45 ` Stephen Warren
2012-11-09 2:26 ` David Gibson
2012-11-09 15:40 ` Pantelis Antoniou
2012-11-13 0:03 ` David Gibson
2012-11-09 21:08 ` Grant Likely
2012-11-13 0:05 ` David Gibson
2012-11-09 21:42 ` Grant Likely
2012-11-13 1:05 ` David Gibson
2012-11-13 5:22 ` Stephen Warren
2012-11-13 6:54 ` David Gibson
2012-11-09 22:57 ` Stephen Warren
2012-11-09 23:27 ` Grant Likely
2012-11-12 12:05 ` Pantelis Antoniou
2012-11-09 23:14 ` Stephen Warren
2012-11-09 23:06 ` Stephen Warren
2012-11-09 23:32 ` Grant Likely
2012-11-12 11:03 ` Koen Kooi
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