Re: [RFC 6/6] xen/arm: Replace early_printk call to printk call

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

On 20/02/14 11:05, Ian Campbell wrote:
> On Thu, 2014-02-20 at 11:01 +0000, Julien Grall wrote:
>>
>> On 20/02/14 09:04, Ian Campbell wrote:
>>> I was actually thinking more along the lines of a .word at a defined
>>> offset which you could hex edit to a specific value to activate a
>>> particular flavour of early printk handling. That would be sufficient
>>> e.g. for osstest to activate the appropriate stuff for the specific
>>> platform.
>>
>> I don't see useful use case to have a such early printk implementation
>> in Xen. When the board is fully supported, failed at early stage (e.g
>> before console is initialized) is very unlikely. At least if you don't
>> play with memory.
>
> a) there are boards which aren't fully supported, getting some debug out
> of a distro package might be useful

Few months ago we have decided to allow early printk only when Xen is 
compiled with debug enabled. It seems a big mistake to ship distro with 
debug enabled :).

> b) even for boards which are fully supported there may still be bugs
> which only appear under particular circumstances.

I understand this use case. If I understand your previous mail the 
solution would me "Hex editing manually the Xen binary to set the early 
printk", right? If so, you are assuming that the distro (or anything 
else) is proving the zImage. Otherwise the developper has to:
    - unpack from the uImage
    - editing the zImage
    - recreate the uImage

That seems very complicated compare to recompiling Xen...

-- 
Julien Grall