Re: [PATCH] s390/net: lcs: use IS_ENABLED() for kconfig detection

Simon Horman
2023-06-21T15:53:17Z

On Tue, Jun 20, 2023 at 07:35:17PM -0700, Randy Dunlap wrote:
> Hi,
>
> On 6/15/23 15:21, Randy Dunlap wrote:
> > When CONFIG_ETHERNET=m or CONFIG_FDDI=m, lcs.s has build errors or
> > warnings:
> >
> > ../drivers/s390/net/lcs.c:40:2: error: #error Cannot compile lcs.c without some net devices switched on.
> > 40 | #error Cannot compile lcs.c without some net devices switched on.
> > ../drivers/s390/net/lcs.c: In function 'lcs_startlan_auto':
> > ../drivers/s390/net/lcs.c:1601:13: warning: unused variable 'rc' [-Wunused-variable]
> > 1601 | int rc;
> >
> > Solve this by using IS_ENABLED(CONFIG_symbol) instead of ifdef
> > CONFIG_symbol. The latter only works for builtin (=y) values
> > while IS_ENABLED() works for builtin or modular values.
> >
> > Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
> > Cc: Alexandra Winter <wintera@linux.ibm.com>
> > Cc: Wenjia Zhang <wenjia@linux.ibm.com>
> > Cc: linux-s390@vger.kernel.org
> > Cc: netdev@vger.kernel.org
> > Cc: Heiko Carstens <hca@linux.ibm.com>
> > Cc: Vasily Gorbik <gor@linux.ibm.com>
> > Cc: Alexander Gordeev <agordeev@linux.ibm.com>
> > Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
> > Cc: Sven Schnelle <svens@linux.ibm.com>
> > ---
> > drivers/s390/net/lcs.c | 10 +++++-----
> > 1 file changed, 5 insertions(+), 5 deletions(-)
> >
> > diff -- a/drivers/s390/net/lcs.c b/drivers/s390/net/lcs.c
> > --- a/drivers/s390/net/lcs.c
> > +++ b/drivers/s390/net/lcs.c
> > @@ -36,7 +36,7 @@
> > #include "lcs.h"
> >
> >
> > -#if !defined(CONFIG_ETHERNET) && !defined(CONFIG_FDDI)
> > +#if !IS_ENABLED(CONFIG_ETHERNET) && !IS_ENABLED(CONFIG_FDDI)
> > #error Cannot compile lcs.c without some net devices switched on.
> > #endif
> >
> > @@ -1601,14 +1601,14 @@ lcs_startlan_auto(struct lcs_card *card)
> > int rc;
> >
> > LCS_DBF_TEXT(2, trace, "strtauto");
> > -#ifdef CONFIG_ETHERNET
> > +#if IS_ENABLED(CONFIG_ETHERNET)
> > card->lan_type = LCS_FRAME_TYPE_ENET;
> > rc = lcs_send_startlan(card, LCS_INITIATOR_TCPIP);
> > if (rc == 0)
> > return 0;
> >
> > #endif
> > -#ifdef CONFIG_FDDI
> > +#if IS_ENABLED(CONFIG_FDDI)
> > card->lan_type = LCS_FRAME_TYPE_FDDI;
> > rc = lcs_send_startlan(card, LCS_INITIATOR_TCPIP);
> > if (rc == 0)
> > @@ -2139,13 +2139,13 @@ lcs_new_device(struct ccwgroup_device *c
> > goto netdev_out;
> > }
> > switch (card->lan_type) {
> > -#ifdef CONFIG_ETHERNET
> > +#if IS_ENABLED(CONFIG_ETHERNET)
> > case LCS_FRAME_TYPE_ENET:
> > card->lan_type_trans = eth_type_trans;
> > dev = alloc_etherdev(0);
> > break;
> > #endif
> > -#ifdef CONFIG_FDDI
> > +#if IS_ENABLED(CONFIG_FDDI)
> > case LCS_FRAME_TYPE_FDDI:
> > card->lan_type_trans = fddi_type_trans;
> > dev = alloc_fddidev(0);
>
>
> kernel test robot reports build errors from this patch when
> ETHERNET=y, FDDI=m, LCS=y:
>
> https://lore.kernel.org/all/202306202129.pl0AqK8G-lkp@intel.com/
>
> Since the code before my patch expected (supported) FDDI=y only
> (by checking for CONFIG_FDDI only and not checking for CONFIG_FDDI_MODULE),
> the best solution that I can see is to enforce that expectation in
> drivers/s390/net/Kconfig:
>
> diff -- a/drivers/s390/net/Kconfig b/drivers/s390/net/Kconfig
> --- a/drivers/s390/net/Kconfig
> +++ b/drivers/s390/net/Kconfig
> @@ -5,7 +5,7 @@ menu "S/390 network device drivers"
> config LCS
> def_tristate m
> prompt "Lan Channel Station Interface"
> - depends on CCW && NETDEVICES && (ETHERNET || FDDI)
> + depends on CCW && NETDEVICES && (ETHERNET || FDDI = y)

Hi Randy,

Unfortunately I don't think this helps.
In the config given at the link above, ETHERNET is y.
And the error regarding fddi_type_trans and alloc_fddidev being undefined
seems to occur regardless of your change.

I did have better luck with this.

diff --git a/drivers/s390/net/Kconfig b/drivers/s390/net/Kconfig
index 9c67b97faba2..303220251495 100644
--- a/drivers/s390/net/Kconfig
+++ b/drivers/s390/net/Kconfig
@@ -6,6 +6,7 @@ config LCS
def_tristate m
prompt "Lan Channel Station Interface"
depends on CCW && NETDEVICES && (ETHERNET || FDDI)
+ depends on FDDI=y || FDDI=n
help
Select this option if you want to use LCS networking on IBM System z.
This device driver supports FDDI (IEEE 802.7) and Ethernet.

I am assuming that LCS=m and FDDI=m can't work at runtime
because there is no guarantee that FDDI is loaded before LCS.
But I could well be wrong here.

> help
> Select this option if you want to use LCS networking on IBM System z.
> This device driver supports FDDI (IEEE 802.7) and Ethernet.
>
> What do people think of that change?
> Any other ideas/suggestions?
>
> thanks.
> --
> ~Randy
>