[RFC PATCH 0/9] dt: dependencies (for deterministic driver initialization order based on the DT)

Alexander Holler holler at ahsoftware.de
Wed May 14 09:23:13 PDT 2014

Am 14.05.2014 18:05, schrieb Grant Likely:
> On Wed, May 14, 2014 at 4:02 PM, Alexander Holler <holler at ahsoftware.de> wrote:
>> Am 14.05.2014 16:19, schrieb Grant Likely:
>>> Rather than a dtb schema change, for the most common properties (irqs,
>>> clocks, gpios), we could extract dependencies at boot time. I don't like
>>> the idea of adding a separate depends-on property because it is very
>>> easy to get it out of sync with the actual binding data (dtc is not the
>>> only tool that manipulates .dtbs. Firmware will fiddle with it too).
>> Then that stuff has to fiddle correct. Sorry, but trying to solve all
>> problems right from the beginning just leads to endless talks with no end
>> and nothing will happen at all because nobody aggrees how to start.
> I appreciate the problem that you're trying to solve and why you're
> using the dtc approach. My job is to poke at the solution and make
> sure it is going to be reliable. Making sure all users know how to
> fiddle with the new property correctly is not a trivial problem,
> especially when it is firmware that will not necessarily be updated.

The answer is just that they don't have to use this feature.

It is more meant as a long-term solution to fix for the problem of 
increasing hard-coded workarounds which all are trying to fix the 
initialization order of drivers. Hardware has become a lot more 
complicated than it was in the good old days, and I think the time is 
right trying to adopt the init-system to this new century instead of 
still adding workarounds here and there.

> I'm not saying flat out 'no' here, but before I merge anything, I have
> to be reasonably certain that the feature is not going to represent a
> maintenance nightmare over the long term.

The maintenance nightmare is already present in form of all the 
workarounds which are trying to fix the initialzation order necessary 
for modern hardware.



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