How to set dependency in kernel module package?

For Developers
1

Hello all,
i created a new hwmon driver package which needs CONFIG_REGMAP set in kernel config.
But this variable is not set bydefault in my target config.

When i add another kernel module which requires these settings with
make menuconfig (e.g. kmod-hwmon-lm75) , also my driver compiles without error.
But without this workaround CONFIG_REMAP is not set and compilation fails.

What i've done so far:

What am i missing?

2

It looks like the lantiq atm packages do this with kmod-atm, so it should be possible: https://github.com/openwrt/openwrt/blob/f0445746f6fd96fc7c5394b238153bd2ff22bc5b/package/kernel/lantiq/ltq-atm/Makefile#L24

Some suggestions:

  • Check tmp/.config-package.in to see that your package dependencies are being parsed correctly. Sometimes, I need to manually remove this tmp folder to get config to update correctly.
  • don't include in KCONFIG Kconfigs that you depend on packages for (HWMON I2C REGMAP_I2C)
  • You should be able to use KERNEL_MAKE
  • Might be easier to remove the Kconfig your driver defines: https://github.com/openwrt/openwrt/commit/24bf94ecb728d47d45ec9a419b92bb8440eb64ce
  • I think, because you are not building this driver as part of the kernel build, the KernelPackage KCONFIG should be empty—this is what the other src kernel packages do, see: git grep KCONFIG -- 'package/kernel/**Makefile' ':!package/kernel/linux'
  • Check other examples of KernelPackage build from source: find package/kernel/ -maxdepth 2 -type d -iname src -printf '%h\n'
3

Thanks for your suggestions, but meanwhile i think it is not possible to add an required kernel config for a package which is not part of the kernel tree.

It looks like the lantiq atm packages do this with kmod-atm , so it should be possible:

Promising, but i think the kmod-atm dependecy is already set in the target configs,
as these packages can't be added to other targets.

  • Check tmp/.config-package.in to see that your package dependencies are being parsed correctly.

It looks good, all dependencies are here, but in kernel config CONFIG_REGMAP_I2C is missing.

  • don't include in KCONFIG Kconfigs that you depend on packages for (HWMON I2C REGMAP_I2C)

Removed it, but no change.

  • You should be able to use KERNEL_MAKE

Still no success.

  • Might be easier to remove the Kconfig your driver defines:

Also no change.

  • I think, because you are not building this driver as part of the kernel build, the KernelPackage KCONFIG should be empty

O.k., but the dependency is still missing.

  • Check other examples of KernelPackage build from source: find package/kernel/ -maxdepth 2 -type d -iname src -printf '%h\n'

I didn't find a good example here, they have either no dependencies or are target depended, so all dependcies are set already be the target.

Meanwhile i think i should move my driver to the kernel tree like ubnt-ledbar, see:
target/linux/generic/hack-5.xx/800-ubnt-ledbar-driver-patch and
target/linux/generic/files/drivers/leds/leds_ubnt-ledbar.c

Or better add patches under package/kernel/hwmon-isl28022 ?
Any thoughts on it?

4

It is not (directly). There may be something that select or depends on it:

git grep CONFIG_ATM -- target/linux/lantiq/
git grep kmod-atm -- target/linux/lantiq

This is due to the DEPENDS on @TARGET_lantiq_$ part of the KernelPackage

These packages are included in DEVICE_PACKAGES of the images, which might help getting this to work.

kmod-ovpn-dco is another example: https://github.com/openwrt/packages/blob/master/kernel/ovpn-dco/Makefile

Just making sure that you are checking the kernel config after it has been parsed, under build_dir/target-*/linux-*/linux-*/.config*

Yes, building this within kernel means let Makefile complexity. That driver was moved out to a package though: https://github.com/openwrt/openwrt/commit/4363faef8a8c975410f001858b010170942aacfc

The patches under package modify the source defined by the package, so that will not help here.

5

kmod-ovpn-dco is another example

Very interesting exampe, this package does exactly what i want.
I enabled 'kmod-ovpn-dco', the dependecies are set correctly and the build succeeds.

But i don't see yet what's the difference to my package.

Just making sure that you are checking the kernel config after it has been parsed, under build_dir/target-/linux-/linux-/.config

I have

  • .config.set, .config.prev and .config.old with the identical content and CONFIG_REGMAP_I2C=m set as needed.
  • .config.override with CONFIG_REGMAP_I2C=m (smaller content compared to .config.set)
  • .config and .config.modules.save which are identical and
    # CONFIG_REGMAP_I2C is not set which causes the trouble

For kmod-ovpn-dco the dependency CONFIG_NET_UDP_TUNNEL=m is set in all .config* files.

From the timestamps, .config is the newest one, but i need a make with V=sc to see what happens.

6

Good information. This means that Openwrt is correctly setting the Kconfig options https://github.com/openwrt/openwrt/blob/9a5b1af670185f07a797920f861a6033e61c5c61/include/kernel-defaults.mk#L114, but then configure run by the kernel is dropping them.
I think this could be because REGMAP_I2C is hidden option (no prompt text), so kernel configure will drop it unless something else select or depends on it (from kernel .config). If that is the case, I think you will need to move your driver into the kernel build. I saw something similar (hidden .config option dropped) with kmod-sfp (not) being built by itself.

7

I think this could be because REGMAP_I2C is hidden option (no prompt text)

I removed the HIDDEN flag from both regmap-i2c and regmap, but build still fails.

kmod-ovpn-dco depends on udptunnel4 and udptunnel6 which both are hidden too.
Therefore i think the HIDDEN flag is not the reason.

8

HIDDEN at OpenWrt level does not matter (relevant for OpenWrt make menuconfig)
We are looking at something that happens within the kernel build process: I think that no prompt text in kernel Kconfig does matter does matter here. Example:

config REGMAP_I2C
	tristate
	depends on I2C

vs.

config I2C
	tristate "I2C support"

The way to test this is to patch it in kernel, example:

config REGMAP_I2C
	tristate "REGMAP I2C support"
	depends on I2C

This can be done in-place, under build_dir/target-*/linux-*/linux-*/drivers/i2c/Kconfig, then rebuild kernel via make target/linux/install, but it is easy to make mistakes, and you will lose changes when a clean happens.

9

O.k. this works, i think i have to create a patch similar to
target/linux/generic/hack-5.15/261-lib-arc4-unhide.patch

Can i add such a patch to my PR, or is it better to create separate PRs?

10

PR created

11

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