[ewg] Re: [ofa-general] ofed autoconf.h

[Steve Wise]

>> I'll run experiments.
>>     
>
> I just did.  It seems to work as I thought.  You do get macro
> redefinition warnings though for something defined in both files:
>
> bar/a.h:1:1: warning: "FOO" redefined
>
> which will be an error if you build with -Werror.  :-(
>
> If including the kernel's autoconf.h *before* doing all of the OFED
> macros is the right solution (which I think it is) the warnings can be
> fixed by doing:
>
> #include_next <autoconf.h>
>
>   

Ok we'll do this for 1538 and push it into ofed-1.4.1.


> But relative to bug 1578, I'd only want to see macros which are to be
> set to something "#undef"ed first and not have every macro "#undef"ed
> wholesale.
>
>   

Yup.


>   
>> You have to rebuild/reinstall ofed if you change the backing kernel.
>>     
>
> Hrm.  Even if I change something completely unrelated to OFED or
> networking at all, like say just changing CONFIG_SERIAL_8250 from m to
> y?
>
>   

Probably not.  But as a rule, the build of ofed is against a specific 
kernel and configuration.  Change the backing kernel config can cause 
problems unless you rebuild.  Especially if module versioning is on.


>   
>> This does expose an issue, however.  If an ofed release changes the 
>> kernel verbs or cm APIs, then it can break  any rdma kernel modules that 
>> do not get rebuilt against the ofed headers.  But this issue has always 
>> been there I guess. 
>>     
>
> Yeah.  I was considering that as well WRT to bug 1578 and not wholesale
> "#undef"ing all macros leading to a mixture of kernel provided and OFED
> provided RDMA options.
>
> I wonder if this is something that is appropriate to do at (OFED0
> configure time, and simply bail if a mismatch is found with a "you can't
> do that.  either change your ofed selections or disable FOO in your
> kernel configuration" type error message.
>   

Gimme an example of what you mean?


> I don't think this particular problem is something we need to address
> for 1.4.1 though.
>
>   

So 1578 can be deferred?


Steve.