refactor(tinyusb_msc): Device callbacks

[roma-jam]

Requirements

The idea is to unmount the EMMC and finalize the EMMC transactions gracefully before MSC takes control of the EMMC. From what we've seen, the MSC takes over the EMMC at the moment the USB is plugged-in without any notification.

Reference link: https://esp32.com/viewtopic.php?f=13&t=34535

However, please consider a bit of polishing and adding more comments in future follow-ups.

Reference link: espressif/idf-extra-components#210 (review)

Description

This is a refactoring of currently present logic of MSC storage callbacks.

Changes simplify the callback logic by:

• merging the callbacks into one callback with event_id and options argument.
• decreasing amount of the code
• splitting the code for spiflash and sdmmc to increase code clarity in tinyusb_msc.

Key Features

1. Curved out storage code from tusb_msc_storage.c. Now, the spiflash and sdmmc have their own storage logic, available by the common API for the MSC storage.
2. Renamed tusb_msc_storage.c to tinyusb_msc.c. The rule is: all the upstream code from TinyUSB starts with tusb_* all additional code from our side starts with tinyusb_*. For example: tinyusb_task.c, tinyusb_msc.c and so on.
3. Introduced the dynamic configuration for the storage type: TINYUSB_MSC_STORAGE_TYPE_SPIFLASH or TINYUSB_MSC_STORAGE_TYPE_SDMMC. Only one function for the driver installation: tinyusb_msc_storage_init(&config).
4. Added possibility to select mount point (APP or USB) during the driver installation. User can select config.mount_point = TINYUSB_MSC_STORAGE_MOUNT_APP, and after driver installation the storage will be mounted to the APP. Valuable, when device is self_powered and we need to access the storage from the APP before the device
   will be connected to the USB Host.
5. Merged the callbacks to the one callback with user argument.
6. Added the FS format flags configuration (instead of build-time Kconfig)

Related

• MSC premount callbacks were intoduced in esp_tinyusb: add MSC pre mount/unmount changed event and callback idf-extra-components#210
• Follow-up for feat(tusb_msc): Add device mount/unmount callback #122

Testing

• Added a test application msc_storage, based on the spiflash that verifies the callbacks presence, mounting logic and memory leakages during intall/uninstall.

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Checklist

Before submitting a Pull Request, please ensure the following:

• 🚨 This PR does not introduce breaking changes.
• All CI checks (GH Actions) pass.
• Documentation is updated as needed.
• Tests are updated or added as necessary.
• Code is well-commented, especially in complex areas.
• Git history is clean — commits are squashed to the minimum necessary.