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SubjectRE: [PATCH] iwlwifi: work around reverse dependency on MEI
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Hi Arend,

> Subject: [PATCH] iwlwifi: work around reverse dependency on MEI
>
> From: Arnd Bergmann <arnd@arndb.de>
>
> If the iwlmei code is a loadable module, the main iwlwifi driver cannot be
> built-in:
>
> x86_64-linux-ld: drivers/net/wireless/intel/iwlwifi/pcie/trans.o: in function
> `iwl_pcie_prepare_card_hw':
> trans.c:(.text+0x4158): undefined reference to `iwl_mei_is_connected'
>
> Unfortunately, Kconfig enforces the opposite, forcing the MEI driver to not
> be built-in if iwlwifi is a module.
>
> There is no easy way to express the correct dependency in Kconfig, this is the
> best workaround I could come up with, turning CONFIG_IWLMEI into a 'bool'
> symbol, and spelling out the exact conditions under which it may be enabled,
> and then using Makefile logic to ensure it is built-in when iwlwifi is.
>
> A better option would be change iwl_mei_is_connected() so it could be
> called from iwlwifi regardless of whether the mei driver is reachable, but that
> requires a larger rework in the driver.

I can try to do that but I don't really see how..
I can't really make a function that would behave differently based on whether the symbol is available or not.

>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> drivers/net/wireless/intel/iwlwifi/Kconfig | 6 +++---
> drivers/net/wireless/intel/iwlwifi/Makefile | 3 +--
> drivers/net/wireless/intel/iwlwifi/mei/Makefile | 4 +++-
> 3 files changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/net/wireless/intel/iwlwifi/Kconfig
> b/drivers/net/wireless/intel/iwlwifi/Kconfig
> index cf1125d84929..474afc6f82a8 100644
> --- a/drivers/net/wireless/intel/iwlwifi/Kconfig
> +++ b/drivers/net/wireless/intel/iwlwifi/Kconfig
> @@ -93,10 +93,10 @@ config IWLWIFI_BCAST_FILTERING
> expect incoming broadcasts for their normal operations.
>
> config IWLMEI
> - tristate "Intel Management Engine communication over WLAN"
> - depends on INTEL_MEI
> + bool "Intel Management Engine communication over WLAN"
> + depends on INTEL_MEI=y || INTEL_MEI=IWLMVM
> + depends on IWLMVM=y || IWLWIFI=m
> depends on PM
> - depends on IWLMVM
> help
> Enables the iwlmei kernel module.

Johannes suggested to make IWLMVM depend on IWLMEI || !IWLMEI
That worked as well, I just had issues with this in our internal backport based tree.
I need to spend a bit more time on this, but I admit my total ignorance in Kconfig's dialect.


>
> diff --git a/drivers/net/wireless/intel/iwlwifi/Makefile
> b/drivers/net/wireless/intel/iwlwifi/Makefile
> index 75a703eb1bdf..c117e105fe5c 100644
> --- a/drivers/net/wireless/intel/iwlwifi/Makefile
> +++ b/drivers/net/wireless/intel/iwlwifi/Makefile
> @@ -29,7 +29,6 @@ iwlwifi-$(CONFIG_IWLWIFI_DEVICE_TRACING) += iwl-
> devtrace.o ccflags-y += -I$(src)
>
> obj-$(CONFIG_IWLDVM) += dvm/
> -obj-$(CONFIG_IWLMVM) += mvm/
> -obj-$(CONFIG_IWLMEI) += mei/
> +obj-$(CONFIG_IWLMVM) += mvm/ mei/
>
> CFLAGS_iwl-devtrace.o := -I$(src)
> diff --git a/drivers/net/wireless/intel/iwlwifi/mei/Makefile
> b/drivers/net/wireless/intel/iwlwifi/mei/Makefile
> index 8e3ef0347db7..98b561c3820f 100644
> --- a/drivers/net/wireless/intel/iwlwifi/mei/Makefile
> +++ b/drivers/net/wireless/intel/iwlwifi/mei/Makefile
> @@ -1,5 +1,7 @@
> # SPDX-License-Identifier: GPL-2.0-only
> -obj-$(CONFIG_IWLMEI) += iwlmei.o
> +ifdef CONFIG_IWLMEI
> +obj-$(CONFIG_IWLWIFI) += iwlmei.o
> +endif
> iwlmei-y += main.o
> iwlmei-y += net.o
> iwlmei-$(CONFIG_IWLWIFI_DEVICE_TRACING) += trace.o
> --
> 2.29.2

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