From: Mitch Bradley <wmb@firmworks.com>
To: Koen Kooi <koen@dominion.thruhere.net>
Cc: Ryan Mallon <rmallon@gmail.com>, Kevin Hilman <khilman@ti.com>,
Wood Scott-B07421 <B07421@freescale.com>,
Matt Porter <mporter@ti.com>,
Tabi Timur-B04825 <B04825@freescale.com>,
"devicetree-discuss@lists.ozlabs.org"
<devicetree-discuss@lists.ozlabs.org>,
Pantelis Antoniou <panto@antoniou-consulting.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Felipe Balbi <balbi@ti.com>, Deepak Saxena <dsaxena@linaro.org>,
Russ Dill <Russ.Dill@ti.com>,
"linux-omap@vger.kernel.org" <linux-omap@vger.kernel.org>
Subject: Re: [RFC] Device Tree Overlays Proposal (Was Re: capebus moving omap_devices to mach-omap2)
Date: Thu, 08 Nov 2012 07:00:47 -1000 [thread overview]
Message-ID: <509BE53F.4040609@firmworks.com> (raw)
In-Reply-To: <356155A1-776B-4AA5-A912-14CE7D9AE42C@dominion.thruhere.net>
On 11/8/2012 3:28 AM, Koen Kooi wrote:
>
> Op 7 nov. 2012, om 23:35 heeft Ryan Mallon <rmallon@gmail.com> het volgende geschreven:
>
>> On 06/11/12 08:40, Tabi Timur-B04825 wrote:
>>> On Mon, Nov 5, 2012 at 2:40 PM, Grant Likely <grant.likely@secretlab.ca> wrote:
>>>
>>>> Jane is building custom BeagleBone expansion boards called 'capes'. She
>>>> can boot the system with a stock BeagleBoard device tree, but additional
>>>> data is needed before a cape can be used. She could replace the FDT file
>>>> used by U-Boot with one that contains the extra data, but she uses the
>>>> same Linux system image regardless of the cape, and it is inconvenient
>>>> to have to select a different device tree at boot time depending on the
>>>> cape.
>>>
>>> What's wrong with having the boot loader detect the presence of the
>>> Cape and update the device tree accordingly? We do this all the time
>>> in U-Boot. Doing stuff like reading EEPROMs and testing for the
>>> presence of hardware is easier in U-Boot than in Linux.
>>
>> This is probably okay for some hardware, but doesn't work in the general
>> case. Not all hardware is detectable, for example a cape which just adds
>> a set of LEDs for GPIO pins. Also, some hardware might not easily be
>> detectable without adding additional complexity to the boot loader.
>
> And as Pantelis mentioned before, I really don't want my users to change the bootloader whenever they add a new LED. Touching the bootloader is just too accident prone, we had a ton of RMA requests for older versions of the beagleboard from people trying to upgrade u-boot.
One possibility for dynamic device tree mods would be to run Open
Firmware from u-boot and have it generate the device tree and possibly
modify it either interactively or from a script loaded from a file or
the network. OFW could then either load Linux directly or return to
u-boot, which would proceed with loading.
>
> Apart from the above I'd like to have fewer points of failure. Right now I need to keep uImage and foo.dtb in sync and I hate to add u-boot to that equasion as well.
>
> regards,
>
> Koen
> _______________________________________________
> devicetree-discuss mailing list
> devicetree-discuss@lists.ozlabs.org
> https://lists.ozlabs.org/listinfo/devicetree-discuss
>
next prev parent reply other threads:[~2012-11-08 17:01 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 [this message]
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
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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