Re: [Linaro-uefi] [PATCH] xen: arm: implement generic multiboot compatibility strings (Was: Re: The GRUB multiboot support patch for aarch64(V3.1))

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

On 06/06/2014 01:32 PM, Ian Campbell wrote:
> On Fri, 2014-06-06 at 13:28 +0100, Julien Grall wrote:
>> On 06/06/2014 01:24 PM, Fu Wei wrote:
>>> On 06/06/2014 02:31 AM, Ian Campbell wrote:
>>>> On Thu, 2014-06-05 at 18:03 +0100, Julien Grall wrote:
>>>>>>> While we are modifying the protocol, "linux-zImage" is confusing in the
>>>>>>> name. Actually we can use it for an ELF, another OS... I don't think Xen
>>>>>>> will change his behavior depending of the DOM0 image.
>>>>
>>>> Actually thinking about this some more I think you are right. Xen
>>>> already probes the kernel it gets so we can safely implement this as
>>>> multiboot,kernel, since we don't really need the more specific type. If
>>>> in the future some non-probable kernel comes along which we want to
>>>> support we still have the option of adding more specific compatibility
>>>> strings.
>>>>
>>>> Fu Wei -- if this is OK with you I will modify the wiki page to
>>>> s/multiboot,linux-zimage/multiboot,kernel/ and rev this patch to suit.
>>>
>>> This is OK for me, And I think the "multiboot,kernel" is better and more generic. :-)
>>>
>>>>
>>>> Can we do something similar with linux-ramdisk? I'm not sure since we
>>>> cannot easily probe the ramdisk contents. We could base the ramdisk
>>>> behaviour on the probed behaviour of the kernel. Anyone got any
>>>> thoughts?
>>>
>>> My thought looks exactly the same as yours :
>>> The cpio utility can detect the cpio file format. Maybe we can just probe the file, see if this is a cpio or cpio.gz.
>>
>> cpio is not Linux specific. Probing just the file won't help here to to
>> determine if we have to add the properties linux,initrd-* or another set.
> 
> This can/should be determined by probing the type of kernel which the
> initrd is being passed to, it is not a property of the initrd.

I don't find anything documentation in Linux tree that claim the
linux,initrd-* properties is part of the zImage protocol.

FYI, the device tree documentation in Linux
(Documentation/devicetree/usage-model.txt) is talking about
initrd-{start,end}, not linux,initrd-{start,end}.

If we plan to assume that the zImage always go with linux,initrd*
properties then we have to document this specification somewhere.

Regards,

-- 
Julien Grall