diff mbox series

[net] net: dsa: realtek: fix Kconfig to assure consistent driver linkage

Message ID 20220412155527.1824118-1-alvin@pqrs.dk (mailing list archive)
State Accepted
Commit 2511e0c87786f333c4665508f421ac99e378c719
Delegated to: Netdev Maintainers
Headers show
Series [net] net: dsa: realtek: fix Kconfig to assure consistent driver linkage | expand

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Context Check Description
netdev/tree_selection success Clearly marked for net
netdev/fixes_present success Fixes tag present in non-next series
netdev/subject_prefix success Link
netdev/cover_letter success Single patches do not need cover letters
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/cc_maintainers success CCed 11 of 11 maintainers
netdev/build_clang success Errors and warnings before: 0 this patch: 0
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/verify_fixes success Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 0 this patch: 0
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 55 lines checked
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline success Was 0 now: 0

Commit Message

Alvin Šipraga April 12, 2022, 3:55 p.m. UTC 
From: Alvin Šipraga <alsi@bang-olufsen.dk>

The kernel test robot reported a build failure:

or1k-linux-ld: drivers/net/dsa/realtek/realtek-smi.o:(.rodata+0x16c): undefined reference to `rtl8366rb_variant'

... with the following build configuration:

CONFIG_NET_DSA_REALTEK=y
CONFIG_NET_DSA_REALTEK_SMI=y
CONFIG_NET_DSA_REALTEK_RTL8365MB=y
CONFIG_NET_DSA_REALTEK_RTL8366RB=m

The problem here is that the realtek-smi interface driver gets built-in,
while the rtl8366rb switch subdriver gets built as a module, hence the
symbol rtl8366rb_variant is not reachable when defining the OF device
table in the interface driver.

The Kconfig dependencies don't help in this scenario because they just
say that the subdriver(s) depend on at least one interface driver. In
fact, the subdrivers don't depend on the interface drivers at all, and
can even be built even in their absence. Somewhat strangely, the
interface drivers can also be built in the absence of any subdriver,
BUT, if a subdriver IS enabled, then it must be reachable according to
the linkage of the interface driver: effectively what the IS_REACHABLE()
macro achieves. If it is not reachable, the above kind of linker error
will be observed.

Rather than papering over the above build error by simply using
IS_REACHABLE(), we can do a little better and admit that it is actually
the interface drivers that have a dependency on the subdrivers. So this
patch does exactly that. Specifically, we ensure that:

1. The interface drivers' Kconfig symbols must have a value no greater
   than the value of any subdriver Kconfig symbols.

2. The subdrivers should by default enable both interface drivers, since
   most users probably want at least one of them; those interface
   drivers can be explicitly disabled however.

What this doesn't do is prevent a user from building only a subdriver,
without any interface driver. To that end, add an additional line of
help in the menu to guide users in the right direction.

Link: https://lore.kernel.org/all/202204110757.XIafvVnj-lkp@intel.com/
Reported-by: kernel test robot <lkp@intel.com>
Fixes: aac94001067d ("net: dsa: realtek: add new mdio interface for drivers")
Signed-off-by: Alvin Šipraga <alsi@bang-olufsen.dk>
---

Note that the Fixes: tag could arguably go back to: 

765c39a4fafe ("net: dsa: realtek: convert subdrivers into modules")

... but this would not help the stable branches, since the following
commit (which is the chosen point of my Fixes: tag) changes things a
lot. I will have to send a separate backport for stable.

---
 drivers/net/dsa/realtek/Kconfig | 30 +++++++++++++++++++++---------
 1 file changed, 21 insertions(+), 9 deletions(-)

Comments

patchwork-bot+netdevbpf@kernel.org April 13, 2022, 1:40 p.m. UTC | #1 
Hello:

This patch was applied to netdev/net.git (master)
by David S. Miller <davem@davemloft.net>:

On Tue, 12 Apr 2022 17:55:27 +0200 you wrote:
> From: Alvin Šipraga <alsi@bang-olufsen.dk>
> 
> The kernel test robot reported a build failure:
> 
> or1k-linux-ld: drivers/net/dsa/realtek/realtek-smi.o:(.rodata+0x16c): undefined reference to `rtl8366rb_variant'
> 
> ... with the following build configuration:
> 
> [...]

Here is the summary with links:
  - [net] net: dsa: realtek: fix Kconfig to assure consistent driver linkage
    https://git.kernel.org/netdev/net/c/2511e0c87786

You are awesome, thank you!
patchwork-bot+netdevbpf@kernel.org April 15, 2022, 9 a.m. UTC | #2 
Hello:

This patch was applied to netdev/net-next.git (master)
by David S. Miller <davem@davemloft.net>:

On Tue, 12 Apr 2022 17:55:27 +0200 you wrote:
> From: Alvin Šipraga <alsi@bang-olufsen.dk>
> 
> The kernel test robot reported a build failure:
> 
> or1k-linux-ld: drivers/net/dsa/realtek/realtek-smi.o:(.rodata+0x16c): undefined reference to `rtl8366rb_variant'
> 
> ... with the following build configuration:
> 
> [...]

Here is the summary with links:
  - [net] net: dsa: realtek: fix Kconfig to assure consistent driver linkage
    https://git.kernel.org/netdev/net-next/c/2511e0c87786

You are awesome, thank you!
diff mbox series

Patch

diff --git a/drivers/net/dsa/realtek/Kconfig b/drivers/net/dsa/realtek/Kconfig
index 1aa79735355f..060165a85fb7 100644
--- a/drivers/net/dsa/realtek/Kconfig
+++ b/drivers/net/dsa/realtek/Kconfig
@@ -9,34 +9,46 @@  menuconfig NET_DSA_REALTEK
 	help
 	  Select to enable support for Realtek Ethernet switch chips.
 
+	  Note that at least one interface driver must be enabled for the
+	  subdrivers to be loaded. Moreover, an interface driver cannot achieve
+	  anything without at least one subdriver enabled.
+
+if NET_DSA_REALTEK
+
 config NET_DSA_REALTEK_MDIO
-	tristate "Realtek MDIO connected switch driver"
-	depends on NET_DSA_REALTEK
+	tristate "Realtek MDIO interface driver"
 	depends on OF
+	depends on NET_DSA_REALTEK_RTL8365MB || NET_DSA_REALTEK_RTL8366RB
+	depends on NET_DSA_REALTEK_RTL8365MB || !NET_DSA_REALTEK_RTL8365MB
+	depends on NET_DSA_REALTEK_RTL8366RB || !NET_DSA_REALTEK_RTL8366RB
 	help
 	  Select to enable support for registering switches configured
 	  through MDIO.
 
 config NET_DSA_REALTEK_SMI
-	tristate "Realtek SMI connected switch driver"
-	depends on NET_DSA_REALTEK
+	tristate "Realtek SMI interface driver"
 	depends on OF
+	depends on NET_DSA_REALTEK_RTL8365MB || NET_DSA_REALTEK_RTL8366RB
+	depends on NET_DSA_REALTEK_RTL8365MB || !NET_DSA_REALTEK_RTL8365MB
+	depends on NET_DSA_REALTEK_RTL8366RB || !NET_DSA_REALTEK_RTL8366RB
 	help
 	  Select to enable support for registering switches connected
 	  through SMI.
 
 config NET_DSA_REALTEK_RTL8365MB
 	tristate "Realtek RTL8365MB switch subdriver"
-	depends on NET_DSA_REALTEK
-	depends on NET_DSA_REALTEK_SMI || NET_DSA_REALTEK_MDIO
+	imply NET_DSA_REALTEK_SMI
+	imply NET_DSA_REALTEK_MDIO
 	select NET_DSA_TAG_RTL8_4
 	help
 	  Select to enable support for Realtek RTL8365MB-VC and RTL8367S.
 
 config NET_DSA_REALTEK_RTL8366RB
 	tristate "Realtek RTL8366RB switch subdriver"
-	depends on NET_DSA_REALTEK
-	depends on NET_DSA_REALTEK_SMI || NET_DSA_REALTEK_MDIO
+	imply NET_DSA_REALTEK_SMI
+	imply NET_DSA_REALTEK_MDIO
 	select NET_DSA_TAG_RTL4_A
 	help
-	  Select to enable support for Realtek RTL8366RB
+	  Select to enable support for Realtek RTL8366RB.
+
+endif