TorizonCore Builder - Kernel Module Compiling error

Technical Support
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1

Hello,

I am using an Apalis imx8x module on a custom carrier board. On this carrier we have a M41T81 RTC. I a m trying to compile the rtc-m41-t80.c module from the llinux/drivers/rtc folder. For this i am using the TC Builder and the configured script.

kernel:
    modules:
      - source-dir: modules/m41t81/
        autoload: yes

When the build start i get following errors:

/workdir/modules/m41t81/m41t80.c: In function ‘m41t80_handle_irq’:
/workdir/modules/m41t81/m41t80.c:164:2: error: implicit declaration of function ‘rtc_lock’ [-Werror=implicit-function-declaration]
  164 |  rtc_lock(m41t80->rtc);
      |  ^~~~~~~~
/workdir/modules/m41t81/m41t80.c:168:3: error: implicit declaration of function ‘rtc_unlock’; did you mean ‘osq_unlock’? [-Werror=implicit-function-declaration]
  168 |   rtc_unlock(m41t80->rtc);
      |   ^~~~~~~~~~
      |   osq_unlock
/workdir/modules/m41t81/m41t80.c: In function ‘m41t80_probe’:
/workdir/modules/m41t81/m41t80.c:929:13: error: ‘RTC_FEATURE_ALARM’ undeclared (first use in this function)
  929 |   clear_bit(RTC_FEATURE_ALARM, m41t80_data->rtc->features);
      |             ^~~~~~~~~~~~~~~~~
/workdir/modules/m41t81/m41t80.c:929:13: note: each undeclared identifier is reported only once for each function it appears in
/workdir/modules/m41t81/m41t80.c:929:48: error: ‘struct rtc_device’ has no member named ‘features’
  929 |   clear_bit(RTC_FEATURE_ALARM, m41t80_data->rtc->features);
      |                                                ^~
/workdir/modules/m41t81/m41t80.c:987:7: error: implicit declaration of function ‘devm_rtc_register_device’; did you mean ‘rtc_register_device’? [-Werror=implicit-function-declaration]
  987 |  rc = devm_rtc_register_device(m41t80_data->rtc);
      |       ^~~~~~~~~~~~~~~~~~~~~~~~
      |       rtc_register_device
cc1: some warnings being treated as errors

What extra files do i need to add to the module directory tog et it to build?
Is there another driver that i can use for the m41t81?

Thanks.

2

Greetings @c.gantner,

Please take note of the article: Building External Kernel Modules With Torizon | Toradex Developer Center

The torizoncore-builder tool can only strictly build “out-of-tree” kernel modules, or put simply modules that don’t exist in the Linux kernel. Trying to build a module like rtc-m41t80.c, which does exist in the Linux kernel will generally not work and lead to very strange behaviors.

The only proper way to build an in-tree kernel module. Would be create a customized TorizonCore image with a recompiled kernel that has this kernel module enabled.

Best Regards,
Jeremias

3

Hello Jeremias,

I did not know that. Thank you for clarification.
I already read the article about building external kernel modules and also built one with success.
The issue was with the one “in-the-tree”. As far as i understand i need to build a custom image with Yocto? This would be the next point on my to do list. At the moment i am testing/setting everything up with the Builder.

Regards,
Cristian.

4

Glad I could clarify this.

This would be the ideal approach to avoid any unforeseen issues with adding this driver/module.

Best Regards,
Jeremias

5

Hi @c.gantner,

The Torizon team might be able to enable the device driver as a module in TorizonCore. I’m saying “might” because a few requisites must be met:

  • It shall not break any existing functionality.
  • The device driver must be included in the mainline/upstream.
  • You must provide the kernel configuration that must be enabled to make it work (e.g. CONFIG_XXX, CONFIG_RTC_DRV_M41T80=m, and so on).

If this would help you, and you have the required kernel configs, please provide them so we can evaluate if inclusion is possible.

6

Hello Leo,

Thank you for the help. In the mean time i managed to build a custom image with yocto and apply my customization with the torizon builder.

One of the last open topics is how i can add my own service files via the builder so that when i flash a new module i already have the files inside in the correct location.

Thank you again.

7

Hi @c.gantner, we’re happy to hear you have made progress.

Would you please open a new question about the service configuration files, providing more details? Meanwhile, the article Capturing Changes in the Configuration of a Board on TorizonCore | Toradex Developer Center may help you.