ST7701 LCD driver incorrectly rejects MIPI-DSI interface due to wrong conditional compilation check

[SinKy-Yan]

I'm sorry that I'm not good at expressing myself. The following content is generated by Claude Code.

Bug Description

The ST7701 LCD driver (esp_panel_lcd_st7701.cpp) incorrectly rejects MIPI-DSI interface configuration due to a wrong conditional compilation check. The driver only checks for ESP_PANEL_DRIVERS_BUS_ENABLE_RGB but should also check for ESP_PANEL_DRIVERS_BUS_ENABLE_MIPI_DSI when using MIPI-DSI interface.

Environment

• Platform: ESP32-P4
• Library Version: Latest (ESP32_Display_Panel)
• Interface: MIPI-DSI
• LCD Controller: ST7701

Steps to Reproduce

1. Configure ST7701 with MIPI-DSI interface in esp_panel_board_custom_conf.h:

   #define ESP_PANEL_BOARD_LCD_CONTROLLER      ST7701
   #define ESP_PANEL_BOARD_LCD_BUS_TYPE        (ESP_PANEL_BUS_TYPE_MIPI_DSI)

2. Enable ST7701 driver in esp_panel_drivers_conf.h:

   #define ESP_PANEL_DRIVERS_LCD_USE_ST7701    (1)
   #define ESP_PANEL_DRIVERS_BUS_USE_MIPI_DSI  (1)

3. Compile and run the project.

Expected Behavior

The ST7701 driver should initialize successfully with MIPI-DSI interface.

Actual Behavior

The driver fails with error message:

[E][Panel][esp_panel_lcd_st7701.cpp:0073](init): MIPI-DSI is not supported

Root Cause

In src/drivers/lcd/esp_panel_lcd_st7701.cpp line 64-74, the conditional compilation only checks for RGB bus support:

#if ESP_PANEL_DRIVERS_BUS_ENABLE_RGB
    // Create refresh panel
    ESP_UTILS_CHECK_ERROR_RETURN(
        esp_lcd_new_panel_st7701(
            getBus()->getControlPanelHandle(), getConfig().getDeviceFullConfig(), &refresh_panel
        ), false, "Create refresh panel failed"
    );
    ESP_UTILS_LOGD("Create refresh panel(@%p)", refresh_panel);
#else
    ESP_UTILS_CHECK_FALSE_RETURN(false, false, "MIPI-DSI is not supported");
#endif // ESP_PANEL_DRIVERS_BUS_ENABLE_RGB

However, the underlying esp_lcd_new_panel_st7701() function in src/drivers/lcd/port/esp_lcd_st7701.c correctly supports both RGB and MIPI-DSI interfaces based on the vendor_config->flags.use_mipi_interface flag.

Proposed Fix

Change the conditional compilation check to include MIPI-DSI support:

#if ESP_PANEL_DRIVERS_BUS_ENABLE_RGB || ESP_PANEL_DRIVERS_BUS_ENABLE_MIPI_DSI
    // Create refresh panel
    ESP_UTILS_CHECK_ERROR_RETURN(
        esp_lcd_new_panel_st7701(
            getBus()->getControlPanelHandle(), getConfig().getDeviceFullConfig(), &refresh_panel
        ), false, "Create refresh panel failed"
    );
    ESP_UTILS_LOGD("Create refresh panel(@%p)", refresh_panel);
#else
    ESP_UTILS_CHECK_FALSE_RETURN(false, false, "Neither RGB nor MIPI-DSI is supported");
#endif // ESP_PANEL_DRIVERS_BUS_ENABLE_RGB || ESP_PANEL_DRIVERS_BUS_ENABLE_MIPI_DSI

Additional Context

• ST7701 hardware IC supports both RGB and MIPI-DSI interfaces.
• ESP32-P4 supports MIPI-DSI interface.
• The lower-level driver implementation (esp_lcd_st7701.c) correctly handles both interfaces.
• Only the high-level wrapper has this conditional compilation issue.

Workaround

Currently, users can work around this by adding -DESP_PANEL_DRIVERS_BUS_ENABLE_RGB=1 to build flags, but this is misleading since RGB interface is not actually being used.

[martinroger]

You should propose a PR, sounds like you have the solution !

[SinKy-Yan]

I've submitted this fix in PR #223
Fixes #221