On 02/06/2013 01:33 PM, Jan Kiszka wrote:
> On 2013-02-06 13:31, Gilles Chanteperdrix wrote:
>> On 02/06/2013 01:28 PM, Jan Kiszka wrote:
>>
>>> On 2013-02-06 13:18, Gilles Chanteperdrix wrote:
>>>> On 02/06/2013 11:20 AM, Jan Kiszka wrote:
>>>>
>>>>> Hi Gilles,
>>>>>
>>>>> I just realized that there is now a 8253 clocksource in core-3.4+. How
>>>>> does this work together with Xenomai's TSC emulation via the 8254 in the
>>>>> x86 hal_32? Xenomai reprograms the PIT in rthal_setup_8254_tsc - is this
>>>>> harmless?
>>>>>
>>>>> I came across this while trying to get rid of Xenomai's "depends on
>>>>> !INPUT_PCSPKR" to avoid that circular Kbuild dependency.
>>>>
>>>>
>>>> This emulation replaces Xenomai's TSC emulation when the kernel boots on
>>>> a cpu without a TSC: the detection is made at run-time instead of
>>>> compilation time using self-modifying code (this in order to be able to
>>>> build Debian kernels which boots with any configuration).
>>>
>>> Hmm, that's for the kernel. But what prevents rthal_setup_8254_tsc from
>>> being executed in addition? I'm currently a bit lost in the #ifdefs.
>>
>>
>> rthal_setup_8254_tsc is not called.
>>
>>>
>>>> There is no
>>>> reason to keep the compilation-time dependency on !INPUT_PCSPKR with
>>>> I-pipe core, as now the pc speaker is disabled at run-time too.
>>>> Unfortunately, I could not find how to arrange the Kconfig either.
>>>
>>> As this is only about practically unsupported combinations of Xenomai
>>> (2.6.x) and I-pipe (for kernel 2.6.x) on x86, we could move from a
>>> configure-time to a build-time detection (#ifdef CONFIG_INPUT_PCSPKR ->
>>> BUILD_BUG()).
>>
>>
>> There is already a run-time detection which simply does not declare the
>> PC speaker platform device when there is no tsc.
>
> That's for core-3.4+, but not for older kernels. If we are fine with
> ignoring them, I'll just write a patch to remove that Kconfig dependency.
You could replace !INPUT_PCSPKR with !X86_TSC && !INPUT_PCSPKR
I-pipe core kernels can be compiled with CONFIG_X86_TSC anyway.
--
Gilles.
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