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Before: The cache won't be disabled when XIP on psram. But during flash erasing/programming, read data will be courrupt. When XIP in psram is enabled, the image is not mapped to the cache so usually there will be no flash access. The only way to read from flash is via the driver or use mmap. The driver has protection during erasing, while th mmap region not. Now: Mmap APIs provide a flag to make mmap->unmap region mutually exclusive to flash erase/programming when XIP from psram. SPI Flash write APIs will benefit from this. When the flag is used, no concurrent access to mapped region will happen while writing; otherwise the cache will be disable to avoid data corruption. Most ESP-IDF APIs calls mmap with this flag. As for users calling mmap-like APIs directly, they can choose whether to enable this by a flag. Closes https://github.com/espressif/esp-idf/issues/14897
ESP Flash Chips Directory
Overview
This directory contains header files for implementing custom SPI flash chip drivers. These headers are semi-public - they are intended for expert users who need to implement custom chip drivers for unsupported flash chips, but they are not considered stable API and may change without notice.
Intended Use
These headers are provided for:
- Expert users who need to implement custom chip drivers for flash chips not supported by ESP-IDF
- Advanced developers who need to extend or modify existing chip driver behavior
- Internal ESP-IDF development for implementing official chip drivers
Important Warnings
⚠️ These headers are NOT stable API
- The structure and content of these headers may change in any ESP-IDF release
- No backward compatibility is guaranteed
- These headers are not part of the public API contract
- Changes may break custom chip driver implementations without notice
⚠️ Use at your own risk
- Custom chip drivers using these headers may break when upgrading ESP-IDF
- Thorough testing is required after each ESP-IDF version upgrade
- Consider contributing your chip driver to ESP-IDF or 3rd party flash drivers repo instead of maintaining it separately
Directory Contents
spi_flash_chip_driver.h- Core chip driver interface definitionsesp_flash_types.h- Internal flash type definitionsspi_flash_chip_*.h- Header files for specific chip driver implementations that you may reuse (especially the generic driver)spi_flash_override.h- Flash override configuration structures for those parts outside the scope of esp_flash driver, usually used in the startup code
When to Use These Headers
✅ Appropriate use cases:
- Implementing a driver for a new flash chip model
- Extending functionality of an existing chip driver
- Debugging chip-specific flash issues
See example on how to implement the driver for a custom flash chip.
❌ Not appropriate for:
- Regular application development (use public APIs in
esp_flash.hinstead) - Production code that needs stable API guarantees