usb: device_next: cdc_acm: Fix unused function warning

[tpambor]

Move cdc_acm_send_notification behind the #ifdef CONFIG_UART_LINE_CTRL to avoid unused function warning when config option CONFIG_UART_LINE_CTRL is deactivated.

/home/user/west_workspace/zephyr/subsys/usb/device_next/class/usbd_cdc_acm.c:572:19: warning: unused function 'cdc_acm_send_notification' [-Wunused-function]
  572 | static inline int cdc_acm_send_notification(const struct device *dev,
      |                   ^~~~~~~~~~~~~~~~~~~~~~~~~

[jfischer-no]

There are no "unused function warning when line coding is disabled".

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[jfischer-no]

#96404 (review)

[tpambor]

There are no "unused function warning when line coding is disabled".

Do you mind explaining a bit more? Is your comment about the commit message? I corrected the commit message to "when config option CONFIG_UART_LINE_CTRL is deactivated."

[tpambor]

@jfischer-no You can reproduce the warning compiling samples/subsys/usb/cdc_acm using clang with CONFIG_UART_LINE_CTRL=n.

I tested this using the upcoming zephyr-sdk 0.18.0-alpha4 which includes clang 19.1.7 with
west build -b stm32h573i_dk -- -DZEPHYR_TOOLCHAIN_VARIANT=zephyr/llvm

[jfischer-no]

@jfischer-no You can reproduce the warning compiling samples/subsys/usb/cdc_acm using clang with CONFIG_UART_LINE_CTRL=n.

I tested this using the upcoming zephyr-sdk 0.18.0-alpha4 which includes clang 19.1.7 with west build -b stm32h573i_dk -- -DZEPHYR_TOOLCHAIN_VARIANT=zephyr/llvm

Then it should be fixed in the upcoming toolchain.

[tpambor]

@jfischer-no You can reproduce the warning compiling samples/subsys/usb/cdc_acm using clang with CONFIG_UART_LINE_CTRL=n.
I tested this using the upcoming zephyr-sdk 0.18.0-alpha4 which includes clang 19.1.7 with west build -b stm32h573i_dk -- -DZEPHYR_TOOLCHAIN_VARIANT=zephyr/llvm

Then it should be fixed in the upcoming toolchain.

@jfischer-no I don't get what the issue is here. There is only a single user of cdc_acm_send_notification which is cdc_acm_line_ctrl_set which is only used when CONFIG_UART_LINE_CTRL=y. So cdc_acm_send_notification is certainly unused when CONFIG_UART_LINE_CTRL=n. gcc does not output a warning because this function is static inline but this is just a decision by gcc to not issue unused function warnings for inline functions. Clang issues unused function warnings also for inline functions. This is not a issue of the compiler and clang is a supported compiler as well. The warning can also be reproduced compiling using https://docs.zephyrproject.org/latest/develop/toolchains/arm_toolchain_for_embedded.html.

[ClaCodes]

Then it should be fixed in the upcoming toolchain.

@jfischer-no Could you please bring the debate about, whether or not an unused static inline merits a diagnostic upstream to the clang-compiler-team?

In the mean-time i do not see why this tiny fix should be blocked, could you explain or accept this for the benefit of the project?

[tpambor]

@jfischer-no You can reproduce the warning compiling samples/subsys/usb/cdc_acm using clang with CONFIG_UART_LINE_CTRL=n.
I tested this using the upcoming zephyr-sdk 0.18.0-alpha4 which includes clang 19.1.7 with west build -b stm32h573i_dk -- -DZEPHYR_TOOLCHAIN_VARIANT=zephyr/llvm

Then it should be fixed in the upcoming toolchain.

/cc @stephanosio @keith-packard