AP_Notify: allow display drivers to be disabled

[muramura]

Summary

Allow boards to enable only the AP_Notify display drivers they use.

This adds per-display-driver build options for SSD1306, SH1106, and SITL display backends, while keeping the existing default behavior unchanged.

Classification & Testing (check all that apply and add your own)

• Checked by a human programmer
• Non-functional change
• No-binary change
• Infrastructure change (e.g. unit tests, helper scripts)
• Automated test(s) verify changes (e.g. unit test, autotest)
• Tested manually, description below (e.g. SITL)
• Tested on hardware
• Logs attached
• Logs available on request

Built Copter for esp32s3m5stampfly with extra hwdef settings enabling only SSD1306 display support and disabling SH1106 display support. Confirmed the build succeeds, the final ELF contains Display_SSD1306 symbols, and no Display_SH1106 symbols are present.

Also built Copter for esp32s3m5stampfly with extra hwdef settings enabling only SH1106 display support and disabling SSD1306 display support. Confirmed the build succeeds, the final ELF contains Display_SH1106 symbols, and no Display_SSD1306 symbols are present.

Hardware tested on M5StampFly with a Grove SSD1315 OLED display connected to the I2C Grove port. The display works using the SSD1306 driver with NTF_DISPLAY_TYPE=1.

Description

Some small boards only need one AP_Notify display backend. Before this change, Display.cpp referenced SSD1306, SH1106, and SITL display backends directly whenever display support was enabled. That made it difficult for board-specific hwdef files to include only the display backend they actually use.

This change adds:

• AP_NOTIFY_DISPLAY_SSD1306_ENABLED
• AP_NOTIFY_DISPLAY_SH1106_ENABLED
• AP_NOTIFY_DISPLAY_SITL_ENABLED

The defaults preserve current behavior. Boards can override these defines from hwdef to reduce unused display driver code.

[peterbarker]

Encase all of the relevant source files in the same defines.

i.e. do not rely on the compiler eliding stuff, it's not entirely reliable and does lead to stuff being included when you really don't want it.

[peterbarker]

Suggested change

	// allow boards to include only the display drivers they use
	#ifndef AP_NOTIFY_DISPLAY_SSD1306_ENABLED
	#define AP_NOTIFY_DISPLAY_SSD1306_ENABLED HAL_DISPLAY_ENABLED
	#endif
	#ifndef AP_NOTIFY_DISPLAY_BACKEND_DEFAULT_ENABLED
	#define AP_NOTIFY_DISPLAY_BACKEND_DEFAULT_ENABLED HAL_DISPLAY_ENABLED
	#endif
	// allow boards to include only the display drivers they use
	#ifndef AP_NOTIFY_DISPLAY_SSD1306_ENABLED
	#define AP_NOTIFY_DISPLAY_SSD1306_ENABLED AP_NOTIFY_DISPLAY_BACKEND_DEFAULT_ENABLED
	#endif

[peterbarker]

Suggested change

	#define AP_NOTIFY_DISPLAY_SH1106_ENABLED HAL_DISPLAY_ENABLED
	#define AP_NOTIFY_DISPLAY_SH1106_ENABLED AP_NOTIFY_DISPLAY_BACKEND_DEFAULT_ENABLED

[peterbarker]

Suggested change

	#define AP_NOTIFY_DISPLAY_SITL_ENABLED (HAL_DISPLAY_ENABLED && (CONFIG_HAL_BOARD == HAL_BOARD_SITL))
	#define AP_NOTIFY_DISPLAY_SITL_ENABLED (AP_NOTIFY_DISPLAY_BACKEND_DEFAULT_ENABLED && (CONFIG_HAL_BOARD == HAL_BOARD_SITL))

[peterbarker]

Suggested change

	#endif
	#endif // AP_NOTIFY_DISPLAY_SH1106_ENABLED

similarly elswhere

[muramura]

@peterbarker san
Updated as requested:

• Enclosed all display driver source and header files in their respective #if AP_NOTIFY_DISPLAY_... defines.
• Added AP_NOTIFY_DISPLAY_BACKEND_DEFAULT_ENABLED in AP_Notify_config.h.
• Added comments to #endif directives in Display.cpp.

Thanks for the review!