Re: [PATCH v01 2/3] xen/arm: add platform specific definitions for DRA7 evm board

[Julien Grall <julien.grall@linaro.org>]

On 06/27/2014 03:47 PM, Ian Campbell wrote:
> On Fri, 2014-06-27 at 15:27 +0100, Julien Grall wrote:
>> Hi Ian,
>>
>> On 27/06/14 13:17, Ian Campbell wrote:
>>>> +    /* OMAP Linux kernel handles devices with status "disabled" in a
>>>> +     * weird manner - tries to reset them. While their memory ranges
>>>> +     * are not mapped, this leads to data aborts, so skip these devices
>>>> +     * from DT for dom0.
>>>> +     */
>>>> +    DT_MATCH_NOT_AVAILABLE(),
>>>
>>> I think this should be done in common code, either by default (if that
>>> makes sense) or using a new quirk flag.
>>
>> Both of these solutions doesn't make sense to me. A device which is not 
>> available should not be touch by the kernel. In most of the case, Linux 
>> ignores a device which is not available (see amba/platform register code).
>>
>> For instance, some board has the same SOC but with different devices 
>> enabled/disabled. In this case, there is usually a common device tree 
>> with all enabled/disabled, and a specific device tree which override 
>> some properties.
>>
>> If OMAP does weird thinks with the device tree, then we should keep it 
>> in the platform code.
> 
> That's what the quirks mechanism is for IMHO.

platform_blacklist has been create to blacklist devices for a specific
platform. I don't think other platform will do a such weird think.

handle_node is actually quite complex, there is lots of different case
to skip a node. So I don't feel confident to add a quirk (and therefore
few lines mores) in this function.

So unless there is a good reason to skip blacklist, that does what we
want, I would prefer to use the current solution. And maybe we will be
able to remove it one day...

Regards,

-- 
Julien Grall