Incorrect page size returned from Flash IAP

[LaurentLouf]

Description

• Target STM32F103RCT6
• GNU ARM 7-2017-q4-major
• mbed-cli 1.7.3
• 603c4f9 (HEAD -> master) Merge pull request littlefs: Fixed issue with cleanup in mount function on error #7851 from geky/fix-littlefs-mount-cleanup

A minimal code to reproduce the issue would be :

#include "mbed.h"


// Internal flash interface
FlashIAP internal_flash;

int main() {
    // Initialize internal flash interface
    internal_flash.init();
    printf("Flash start %d, size %d, page size %d\r\n", internal_flash.get_flash_start(),
           internal_flash.get_flash_size(), internal_flash.get_page_size());
}

This issue being that I've got the following response on my target :

Flash start 134217728, size 262144, page size 4

So the flash start and size are coherent with my target, but the page size isn't at all. According to the doc of Flash IAP (https://os.mbed.com/docs/v5.8/mbed-os-api-doxy/classmbed_1_1_flash_i_a_p.html), the value returned is expressed in byte and I highly doubt that I have page sizes of 4 bytes (should be 2kbytes if I recall correctly). I've had to adapt a few files to support my target, but it's been a while and I don't have any problems with the changes made, so I assume that they are mostly correct. So could it be an error with the API of Flash IAP ?

Issue request type

[ ] Question
[ ] Enhancement
[X] Bug

[LMESTM]

@LaurentLouf
the page size definition in mbed is the program page size, which is:

     *  The page size defines the writable page size
     *  @return Size of a program page in bytes

and your STM32 target allows to write the flash down to 4 bytes at a time (you cannot write 1, 2 or 3 bytes only, it has to be be at least 4 bytes), which corresponds to the definition of the page size in mbed.

[LMESTM]

@LaurentLouf
Maybe what you are looking for is

    uint32_t get_sector_size(uint32_t addr) const;

You'll need to use an address because all the sectors may not have the same size.
I agree that "page" and "sector" terminology may not perfectly match between mbed API and STM32 reference manual ...
hope this helps ...

[LaurentLouf]

@LMESTM Well thanks for the quick reply ! I thought about that shortly after posting the question and I have to agree that the terminology is a bit confusing. Thanks for the information about the different sector sizes, I'll have to check that carefully.