USB mass sample not working for FAT FS

[spoerk]

Describe the bug
The USB mass sample does not work for the FAT filesystem.

I want the USB mass sample with the FAT FS configuration as a basis for a new project on the Nordic nRF52840 DK. However, when I configure the sample to use FAT, the FS cannot be mounted.

To Reproduce
Compile the USB mass sample for the nRF52840 DK platform using the following prj.conf:

CONFIG_STDOUT_CONSOLE=y

#USB related configs
CONFIG_USB_DEVICE_STACK=y
CONFIG_USB_DEVICE_PRODUCT="Zephyr MSC sample"
CONFIG_LOG=y
CONFIG_USB_DRIVER_LOG_LEVEL_ERR=y
CONFIG_USB_MASS_STORAGE=y
CONFIG_USB_DEVICE_LOG_LEVEL_ERR=y
CONFIG_USB_MASS_STORAGE_LOG_LEVEL_ERR=y

CONFIG_MAIN_STACK_SIZE=1536

CONFIG_APP_MSC_STORAGE_FLASH_FATFS=y

Expected behavior
The sample should show a successful empty FAT FS over RTT and USB log.

Impact
Was showstopper, now fixed due to great help at Nordic Devzone.

Logs and console output
RTT log output:

[00:00:00.254,333] <err> usb_msc: Storage init ERROR !!!! - Aborting USB init
[00:00:00.258,514] <err> fs: fs mount error (-5)
[00:00:00.258,544] <err> main: Failed to mount filesystem
[00:00:00.258,728] <inf> main: The device is put in USB mass storage mode.

Environment (please complete the following information):

• OS: Windows 11
• Toolchain: Zephyr SDK v2.1.0
• Commit SHA or Version used

Additional context
Simon over at the Nordic Devzone has already solved the problem. His fix should be added to the repo.

[desowin]

The simple solution is to change the "MX25R64" to "mx25r6435f@0" and "GD25Q16" to "gd25q16@0" in samples/subsys/usb/mass/Kconfig. However, it was deemed inappropriate and much more complex solution, involving defining the flashdisk via devicetree binding is in review. See #50856 for more information.

[PerMac]

This bug exposed an issue with validation method of mass samples. Twister is satisfied with a single line:
"The device is put in USB mass storage mode." https://github.com/zephyrproject-rtos/zephyr/blob/main/samples/subsys/usb/mass/sample.yaml#L44 (all configs)
@jfischer-no @desowin Could you propose a multiline output which would validate that full workflow?

[desowin]

@jfischer-no @desowin Could you propose a multiline output which would validate that full workflow?

Example output when the sample works correctly is:

Area 4 at 0x0 on mx25r6435f@0 for 131072 bytes
Mount /NAND:: 0
/NAND:: bsize = 512 ; frsize = 512 ; blocks = 216 ; bfree = 216
/NAND: opendir: 0
End of files
[00:00:00.323,852] <inf> main: The device is put in USB mass storage mode.

Looking for "End of files" in addition to "The device is put in USB mass storage mode" would have caught the issue.