Re: [PATCH] s390/net: lcs: fix build errors when FDDI is a loadable module

Randy Dunlap
2023-06-28T02:53:13Z

Hi,
Sorry for the delay.

On 6/22/23 05:16, Alexandra Winter wrote:
>
>
> On 22.06.23 09:53, Simon Horman wrote:
>> On Thu, Jun 22, 2023 at 09:15:24AM +0200, Alexandra Winter wrote:
>>>
>>>
>>> On 21.06.23 23:37, Randy Dunlap wrote:
>>>> Require FDDI to be built-in if it is used. LCS needs FDDI to be
>>>> built-in to build without errors.
>>>>
>>>> Prevents these build errors:
>>>> s390-linux-ld: drivers/s390/net/lcs.o: in function `lcs_new_device':
>>>> drivers/s390/net/lcs.c:2150: undefined reference to `fddi_type_trans'
>>>> s390-linux-ld: drivers/s390/net/lcs.c:2151: undefined reference to `alloc_fddidev'
>>>>
>>>> This FDDI requirement effectively restores the previous condition
>>>> before the blamed patch, when #ifdef CONFIG_FDDI was used, without
>>>> testing for CONFIG_FDDI_MODULE.
>>>>
>>>> Fixes: 128272336120 ("s390/net: lcs: use IS_ENABLED() for kconfig detection")
> [...]
>>
>>> 2) I wonder whether
>>>
>>> depends on CCW && NETDEVICES && (ETHERNET || FDDI)
>>> + depends on FDDI || FDDI=n
>>>
>>> would do what we want here:
>>> When FDDI is a loadable module, LCS mustn't be built-in.
>>>
>>> I will do some experiments and let you know.
>>
>> It does seem to on my side.
>> But checking would be much appreciated.
>
>
> Here are my experiments:
>
> Current net-next:
> -----------------
> if !IS_ENABLED(CONFIG_ETHERNET) && !IS_ENABLED(CONFIG_FDDI)
>
> drivers/s390/net/KConfig:
> config LCS
> def_tristate m
> depends on CCW && NETDEVICES && (ETHERNET || FDDI)
>
> .config:
> ETHERNET | FDDI | LCS choices | LCS | compile
> --------------------------------------------------------
> n m m,n m success (failed before Randy's fix)
> y m y,m,n m success (failed before Randy's fix)
> y m y fails: undefined reference to `fddi_type_trans'
>
>
> Simon's proposal:
> -----------------
> depends on CCW && NETDEVICES && (ETHERNET || FDDI)
> + depends on FDDI=y || FDDI=n
>
> ETHERNET | FDDI | LCS choices | LCS | compile
> --------------------------------------------------------
> n m -
> y m -
> y m -
> y n y,m,n y success
> y n y,m,n m success
> y y y,m,n m success
>
>
> Alexandra's proposal:
> ---------------------
> depends on CCW && NETDEVICES && (ETHERNET || FDDI)
> + depends on FDDI || FDDI=n
>
> ETHERNET | FDDI | LCS choices | LCS | compile
> --------------------------------------------------------
> n m m,n m success
> y m m,n m success
> y n y,m,n y success
> y n y,m,n m success
> y y y,m,n m success
>
> -----------------------------------------------------------
>
> Seems that
> A[tristate] depends on B[tristate]
> means that A cannot be 'higher' than B.
> Meaning, if B=n -> A= must be n
> if B=m -> A can be m or n
> if B=y -> A can be y or m or n

Looks correct.

> Although I did not find documentation confirming that.

I think that it's in Documentation/kbuild/kconfig-language.rst,
under "Menu dependencies", but not quite in that format. :)

>
> @Randy, do you want give a v2 a try with that?

Sure, I'll try that.

> I guess then it is safe to delete from drivers/s390/net/lcs.c
> -#if !IS_ENABLED(CONFIG_ETHERNET) && !IS_ENABLED(CONFIG_FDDI)
> -#error Cannot compile lcs.c without some net devices switched on.
> -#endif

Yes, I was planning to do that as well.

Thanks for the time that you have spent on this.
--
~Randy