Re: 2.6.29-rc3-git6: Reported regressions from 2.6.28
From: Randy Dunlap
Date: Thu Feb 05 2009 - 14:15:38 EST
Ingo Molnar wrote:
> * Randy Dunlap <randy.dunlap@xxxxxxxxxx> wrote:
>
>> Eric Anholt wrote:
>>> On Wed, 2009-02-04 at 19:56 +0100, Ingo Molnar wrote:
>>>> * Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>>>>
>>>>> On Wed, 4 Feb 2009, Norbert Preining wrote:
>>>>>> The problem is that if you have a configuration under 2.6.28 without
>>>>>> CONFIG_FB and just call make oldconfig, or even make config and don't
>>>>>> know that you loose the DRM. And I was using make oldconfig (there is a
>>>>>> graphical config?? ;-))
>>>>> Sure. It's inconvenient, no question about that. I asked the i915 people
>>>>> to look into not requiring CONFIG_FB, and I hope they will, but my point
>>>>> is that I don't think we can consider "small one-time inconvenience" to be
>>>>> a "regression".
>>>> if you mean that as a general principle, there's four very real downsides in
>>>> my opinion.
>>>>
>>>> Firstly, we could have done better (and still can do better), via various
>>>> easy and non-intrusive measures:
>>>>
>>>> - We could add a runtime warning:
>>>>
>>>> for example a WARN_ONCE("please enable CONFIG_DRM_I915 and CONFIG_FB")
>>>> that there's no DRM because CONFIG_FB is not selected and oldconfig
>>>> loses the I915 setting silently - placed in a key DRM ioctl, would
>>>> have gone a long way addressing the issue. Testers do notice kernel
>>>> warnings that pop up when their X gets slow. (This approach might also
>>>> have the added bonus of warning folks who enable the wrong driver for
>>>> the hardware.)
>>>>
>>>> - Or we could add a more thoughtful Kconfig migration:
>>>>
>>>> Rename DRM_I915 to DRM_I915_FB [which it really is now], and keep
>>>> DRM_I915 as a non-interactive migration helper: if set, it
>>>> auto-selects both FB and DRM_I915_FB.
>>>>
>>>> While CONFIG_FB is an interactive Kconfig option so a select can be
>>>> dangerous to a correct dependency tree, it seems safe to do in this
>>>> specific case because it seems to be a rather leaf entry with no
>>>> dependencies.
>>> I tried select FB. It's the right thing to do. It doesn't work. I
>>> posted to the mailing list two weeks ago about the insane dependency
>>> chain that kbuild comes up with and fails on when we do this, and got
>>> silence.
>> I tried what you had described in that email (from 2 weeks ago), got the
>> same results that you did, but kbuild does seem very confused (to me).
>>
>> reference email from 2+ weeks ago:
>> http://marc.info/?l=linux-kernel&m=123197341316461&w=2
>>
>> Adding Sam to cc.
>
> Check the patch i posted in this thread earlier today, it solves this
> problem.
I saw it. I'd rather kconfig be fixed instead, if possible.
--
~Randy
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