[PATCH 0/3] patches to allow DTB to be appended to the ARM zImage

[robherring2@gmail.com (Rob Herring)]

On 06/14/2011 03:32 PM, Arnd Bergmann wrote:
> On Tuesday 14 June 2011 19:28:49 Nicolas Pitre wrote:
>> On Tue, 14 Jun 2011, Tony Lindgren wrote:
>>
>>> * Nicolas Pitre <nicolas.pitre@linaro.org> [110614 00:04]:
>>>> +
>>>> +   for_each_tag(atag, atag_list) {
>>>> +           if (atag->hdr.tag == ATAG_CMDLINE) {
>>>> +                   setprop_string(dt, "/chosen", "bootargs",
>>>> +                                     atag->u.cmdline.cmdline);
>>>> +           } else if (atag->hdr.tag == ATAG_MEM) {
>>>> +                   uint32_t mem_reg_property[2];
>>>> +                   mem_reg_property[0] = cpu_to_fdt32(atag->u.mem.start);
>>>> +                   mem_reg_property[1] = cpu_to_fdt32(atag->u.mem.size);
>>>> +                   setprop(dt, "/memory", "reg", mem_reg_property,
>>>> +                              sizeof(mem_reg_property));
>>>> +           } else if (atag->hdr.tag == ATAG_INITRD2) {
>>>> +                   uint32_t initrd_start, initrd_size;
>>>> +                   initrd_start = atag->u.initrd.start;
>>>> +                   initrd_size = atag->u.initrd.size;
>>>> +                   setprop_cell(dt, "/chosen", "linux,initrd-start",
>>>> +                                   initrd_start);
>>>> +                   setprop_cell(dt, "/chosen", "linux,initrd-end",
>>>> +                                   initrd_start + initrd_size);
>>>> +           }
>>>> +   }
>>>
>>> I think Russell posted a complete list of the ATAGs to translate
>>> somewhere, but at least ATAG_REVISION is missing here. That's being
>>> used quite a bit as system_rev to set things dynamically.
>>
>> No problem.  This is a work in progress.  We still can test the concept 
>> and fine tune the actual set of ATAGs being translated.
> 
> Let's talk about the revision field now, because it doesn't have a
> direct correspondence in existing attributes.
> 
> Functionality-wise, this would probably be the "compatible" property
> of the root node, with its most specific name to match, but that's not
> trivial to generate.
> 
> In some cases, the system revisions have significant differences in their
> devices (why else would you care about the revision), which means that you
> actually need a different device tree per revision anyway. If that's the
> common case, we could just ignore it completely or instead have a way
> to choose a specific device tree from a list based on the revision.
> 
> Another option would be to merge both the ATAG_REVISION and ATAG_SERIAL
> into a string and put them into the root "serial-number" property that
> is fairly easy to do, but would be harder to parse if you actually rely
> on specific values.
> 

IIRC, system_rev at least can be specified on the kernel command line,
so you could just append the cmd line. However, if you force the
built-in command line to be used that would not work,

Rob