Re: [Qemu-devel] [PATCH v2] arm: add device tree support

[Alexander Graf]

On 01.02.2012, at 02:35, Paul Brook wrote:

>> We could also just change machine->init() and pass the dtb in there. In a
>> QOM world these would become machine device properties anyways.
>> 
>>    machine->init(ram_size, boot_devices,
>>                  kernel_filename, kernel_cmdline, initrd_filename,
>> cpu_model);
>> 
>> Essentially we shouldn't treat -dtb any different than -kernel or -initrd.
>> It's also useful for more than ARM, namely embedded ppc systems. But I can
>> easily post a follow-up patch for those.
> 
> Changing machine->init means you have to touch every single board file, and 
> clone the exact same code for every machine that uses arm_boot.c.  All of 
> which will be rewritten in the near future.

Well, the dt file name would have to be passed into the generic arm_boot.c 
function, yes. But that's something that we need to do at one point in time 
either way, because machines will want to have default dtb file names.

> machine->init is a particularly suckiy interface to start with, we want to be 
> using it less, not more.  It's not like we're going support multiple machine 
> instanced.  At least not before machine->init is removed altogether.

I do see your point on not extending legacy interfaces though and not bloating 
up the patch. In fact, I'm indifferent enough on the actual implementation atm, 
as long as the command line interface (or whatever the user sees) is reasonably 
sane. And it is IMHO. So if it makes everything easier, do it using a global, 
but keep in mind that this will need refactoring.


Alex