Mbed-os: FATFS: FAT16 broken at smallest cluster count

[chrissnow]

Description

• Type: Bug
• Related issue:
• Priority: Blocker Minor

---

Bug

If you have a device that has 4096 512/528b sectors and try to format without specifying the AU it fails.
https://github.com/ARMmbed/mbed-os/blob/20d93bf78d5172b6a0f1c1065058d641e4e0f2e1/features/filesystem/fat/ChaN/ff.cpp#L4172-L4174
Which results in FAT16 as the result since nclst = 0x1000
Yet this then fails here as there is not enough sectors for FAT16
https://github.com/ARMmbed/mbed-os/blob/20d93bf78d5172b6a0f1c1065058d641e4e0f2e1/features/filesystem/fat/ChaN/ff.cpp#L4204-L4207
and returns

FR_MKFS_ABORTED

If you format with an AU of 2

FATFileSystem::format(&flash,2)

It will succeed with FAT12

Expected behavior
Format's the device as FAT12
Actual behavior

FR_MKFS_ABORTED

Steps to reproduce
Use a 16mbit DataFlash which has 4096 sectors of 512/528 (or anything similar)

FATFileSystem::format(&flash); //this fails
FATFileSystem::format(&flash,2);//this works

Further info. https://github.com/ARMmbed/dataflash-driver/issues/3
CC @geky @marcuschangarm

[geky]

Thanks for raising this!

This should also be possible to reproduce with the HeapBlockDevice using @chrissnow's settings (4096 x 512 byte blocks)

internal prioritization IOTMORF-1634

[ciarmcom]

ARM Internal Ref: MBOTRIAGE-150

[yossi2le]

@chrissnow @cmonr @0xc0170 @geky
Hi All
This bug has been opened October 18 2017 and on November 10 2017 the ChanFs was upgraded to R0.13a. I have tried to reproduce the bug but it is not reproducible any more.
So can someone close this bug please?

Thanks

[yossi2le]

@cmonr 10x