Request review of device tree documentation

From: mike@compulab•co.il (Mike Rapoport)
To: linux-arm-kernel@lists•infradead.org
Subject: Request review of device tree documentation
Date: Wed, 16 Jun 2010 09:17:22 +0300	[thread overview]
Message-ID: <4C186C72.2020506@compulab.co.il> (raw)
In-Reply-To: <4C186B7B.1060308@firmworks.com>

Mitch Bradley wrote:
> 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?

Currently it aims to abstract hardware from U-Boot and reuse the same HW 
access code across operating systems and bootloaders. If this code would 
have callbacks I afraid the things would became worse.

> 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
>>>
>>>
>>> _______________________________________________
>>> linux-arm-kernel mailing list
>>> linux-arm-kernel at lists.infradead.org
>>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>>
>>

-- 
Sincerely yours,
Mike.