Re: [PATCH net-next] net: dsa: hellcreek: Add missing TAPRIO dependency

On Thu, Jan 28, 2021 at 5:37 PM Vladimir Oltean [off-list ref] wrote:

On Thu, Jan 28, 2021 at 05:33:38PM +0100, Kurt Kanzenbach wrote:

quoted

Add missing dependency to TAPRIO to avoid build failures such as:

|ERROR: modpost: "taprio_offload_get" [drivers/net/dsa/hirschmann/hellcreek_sw.ko] undefined!
|ERROR: modpost: "taprio_offload_free" [drivers/net/dsa/hirschmann/hellcreek_sw.ko] undefined!

Fixes: 24dfc6eb39b2 ("net: dsa: hellcreek: Add TAPRIO offloading support")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>

Acked-by: Arnd Bergmann <arnd@arndb.de>

Note that for sja1105, Arnd solved it this way. I am still not sure why.

commit 5d294fc483405de9c0913ab744a31e6fa7cb0f40
Author: Arnd Bergmann [off-list ref]
Date:   Fri Oct 25 09:26:35 2019 +0200

    net: dsa: sja1105: improve NET_DSA_SJA1105_TAS dependency

    An earlier bugfix introduced a dependency on CONFIG_NET_SCH_TAPRIO,
    but this missed the case of NET_SCH_TAPRIO=m and NET_DSA_SJA1105=y,
    which still causes a link error:

As I described in this commit, the problem here was that NET_DSA_SJA1105_TAS
is a 'bool' symbol with a dependency on a 'tristate', so you have to prevent
the option from getting enabled when it's part of a driver that gets built into
the kernel but the dependnecy is in a loadable module.

NET_DSA_HIRSCHMANN_HELLCREEK on the other hand is a 'tristate'
symbol itself, so the dependency takes care of it: you cannot set it to =y
when its dependency is =m.

         Arnd