Re: Request review of device tree documentation

From: Mitch Bradley <wmb@firmworks•com>
To: Mike Rapoport <mike@compulab•co.il>
Cc: Nicolas Pitre <nico@fluxnic•net>,
	microblaze-uclinux@itee•uq.edu.au,
	devicetree-discuss <devicetree-discuss@lists•ozlabs.org>,
	Jamie Lokier <jamie@shareable•org>,
	linuxppc-dev <linuxppc-dev@ozlabs•org>,
	Dan Malek <ppc6dev@digitaldans•com>,
	Jeremy Kerr <jeremy.kerr@canonical•com>,
	linux-arm-kernel@lists•infradead.org,
	David Gibson <david@gibson•dropbear.id.au>
Subject: Re: Request review of device tree documentation
Date: Tue, 15 Jun 2010 20:13:15 -1000	[thread overview]
Message-ID: <4C186B7B.1060308@firmworks.com> (raw)
In-Reply-To: <4C186AA8.4040709@compulab.co.il>

Mike Rapoport wrote:
> Mitch Bradley wrote:
>
>> The second topic is the hypothetical use of OFW as a HAL. That will 
>> not happen for several reasons.  The opposition to the idea is 
>> widespread and deeply held, and there are good arguments to support 
>> that opposition.   Furthermore, the economic conditions necessary for 
>> the creation of such a HAL do not exist in the ARM world, nor indeed 
>> in the Linux world in general.  (The necessary condition is the 
>> ability for one company to impose a substantial change by fiat - 
>> essentially a monopoly position.)
>>
>> Shall we agree, then, that any further discussion of the HAL issue is 
>> "just for fun", and that nobody needs to feel threatened that it 
>> would actually happen?
>
> I've recently worked with vendor versions of U-Boot for advanced ARM 
> SoCs. There is already *huge* chunk of HAL code in those versions. And 
> if there would be possibility to have callbacks into the firmware 
> these chunks would only grow, IMHO.

How can there be HAL code in U-Boot unless there is already the 
possibility to have callbacks into the firmware?

It is not HAL if it can't be called.

>
>
>> The potential for "vendors breaking out of the debugging use case and 
>> turning it into a HAL" is miniscule, because
>>
>> a) The callback is disabled by default
>> b) The technical challenges of the callback interface limit its 
>> applicability to specific "wizard user" scenarios
>> c) OFW is unlikely to achieve sufficient market penetration for the 
>> HAL thing to be worth doing
>>
>>
>> _______________________________________________
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>> linux-arm-kernel@lists•infradead.org
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>
>