Re: kdbus: to merge or not to merge?

From: David Lang
Date: Thu Jun 25 2015 - 02:49:23 EST


On Wed, 24 Jun 2015, Greg KH wrote:

On Wed, Jun 24, 2015 at 10:39:52AM -0700, David Lang wrote:
On Wed, 24 Jun 2015, Ingo Molnar wrote:

And the thing is, in hindsight, after such huge flamewars, years down the line,
almost never do I see the following question asked: 'what were we thinking merging
that crap??'. If any question arises it's usually along the lines of: 'what was
the big fuss about?'. So I think by and large the process works.

counterexamples, devfs, tux

Don't knock devfs. It created a lot of things that we take for granted
now with our development model. Off the top of my head, here's a short
list:
- it showed that we can't arbritrary make user/kernel api
changes without working with people outside of the kernel
developer community, and expect people to follow them
- the idea was sound, but the implementation was not, it had
unfixable problems, so to fix those problems, we came up with
better, kernel-wide solutions, forcing us to unify all
device/driver subsystems.
- we were forced to try to document our user/kernel apis better,
hence Documentation/ABI/ was created
- to remove devfs, we had to create a structure of _how_ to
remove features. It took me 2-3 years to be able to finally
delete the devfs code, as the infrastructure and feedback
loops were just not in place before then to allow that to
happen.

So I would strongly argue that merging devfs was a good thing, it
spurned a lot of us to get the job done correctly. Without it, we would
have never seen the need, or had the knowledge of what needed to be
done.

I don't disagree with you, but it was definantly a case of adding something that was later regretted and removed. A lot was learned in the process, but that wasn't the issue I was referring to.

I don't want kdbus to end up the same way. The more I think back to those discussions, the more parallels I see between the two.

David Lang
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