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

Alexandra Winter
2023-06-22T12:16:28Z

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

Although I did not find documentation confirming that.

@Randy, do you want give a v2 a try with 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